Nov 23

Engineering Design and Efficiency of Chevy Volt’s Charge-Sustaining Mode: Builds on GM’s Two-Mode Hybrid Technology

 

[ad#post_ad]I had a discussion with Alex Cattelan, the Chevy Volt’s chief powertrain engineer about the engineering design and operation of the Chevy Volt’s charge sustaining mode.  This is the mode that occurs after the car has depleted the first 40 miles of  range and the gas generator has begun providing electric power.

When you first unveiled the Volt and it was a math model, the car was promoted as getting 50 MPG in generator mode. Now that there are real world parts and parallel hybrid like the Prius verse series. Can you speak about the efficiency difference between series and parallel hybrid operation?
We’re tuning our fuel economy right now. From an architectural perspective there are differences between series and parallel hybrids , there’s absolutely no doubt about that. The issue you mentioned the Volt is a series hybrid when we go into charge sustaining mode or when the engine comes on. We like to think of it not as a hybrid. You’ve got to understand that all of the decisions that we’ve made around this product are made because its an EV. That is the first and foremost thing that it needs to be. So because it is an EV some of the decisions that we’ve made around engine operation will be different than what Toyota makes in its parallel hybrid. For them they are always operating in hybrid mode so they need to optimize everything for engine operation.

In our case we’re optimizing everything for EV operation and the secondary is certainly going to be better than conventional vehicles, but were not necessarily totally optimizing the system for charge sustaining mode because we don’t want to compromise electric vehicle mode.

So to be optimally efficient in charge-sustaining mode you might compromise EV performance?
In the electric vehicle mode, and its not just performance, its efficiency in electric vehicle mode that we’re optimizing.

You mean those first 40 miles?
Right, so you’ve got to remember our principle promise is this is an EV and our engine is there as a range extender and so even when the engine is on, we operate as through we are in EV. All the primary propulsion is satisfied by the electric motor. The engine is really there to supplement power to keep the battery sustained. Now there are a couple of tricks of the trade that we do since we have the engine on more, but for example we don’t want to do a whole lot of gearing that you would do in a parallel hybrid, because none of that is beneficial to you in the EV state.

But doesn’t the fact that you could keep the engine at fixed RPMs also allow you better efficiency?
Actually we don’t keep it at a fixed RPM, we have a window of operation that is optimized. We have been able to optimize the engine for a window of efficiency but it is still best to charge your power and torque levels within that window as the customer torque request varies. We don’t want to always be operating at one state because really you may be putting too much energy into the battery or drawing too much energy out of the battery. It is still good to vary that engine power and torque. Not to follow exactly what the accelerator pedal does, but to optimize efficiency.

We actually have a very sophisticated efficiency calculator in our model within our software. It calculates on a very very short time scale what the driving conditions of the car are. Which mode you are in, whether you turning you engine on or off, and what power and torque you want to run than engine always with the optimization of efficiency in mind as well as managing trade offs for driveability and noise.

We took all of the model that’s in the two mode hybrid and we’ve basically been carving out pieces we don’t need, adding in pieces we do need for this architecture and optimizing that model for this particular vehicle. We didn’t build this from scratch, this is also software that we are using that is also on the 2-mode but we are modifying it for optimizing this architecture.

I’ve driven the 2-mode and notice you can see the switched in mode of operation without feeling it in the car.
Which is the goal, you don’t want you to feel it in the car, we don’t want the customer to know these transitions are taking place, but we need to be able to enable them for efficiency.

With the Volt, once you’re in CS mode you will have a few different windows of operation or just one window for the generator?
We’re optimizing the generator to have different power generating levels. But the beautiful piece of being able to decouple the engine or generator from the axle torque requirement is we can travel along and hit those power levels that we need to optimize the system for battery charging and discharging, we can maneuver across them at any rate of change we so choose.

So think of it as the beauty of being able to decouple the engine is we have a degree of freedom that we don’t have to follow the pedal at all. We can pick and choose the points that are most efficient, we can go between those point on the best path and the most pleasing path to the customer. Actually this is a lot of the work we are doing even on a Prius hybrid every hybrid does it to some extent but every engine is required to follow the pedal. It is much more coupled to the axle torque request than in our vehicle.

It seems to me then you should make CS mode even more efficient then in a car where the engine always has to turn the axle?
Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled. Again were optimizing some of those efficiency point puts we are really doing is focusing on the optimization of the EV. There are trade offs because we absolutely consider this product an EV by nature.

This entry was posted on Monday, November 23rd, 2009 at 7:37 am and is filed under Engineering, Generator, GM Q and A. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

COMMENTS: 159


  1. 1
    Gsned57

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    Nov 23rd, 2009 (7:55 am)

    Sounds to me like he’s pretty much saying the Volt won’t be as efficient in CS mode as the Prius is. Even still I agree that their focus must be on the first 40 miles and if the Volt only gets 40MPG in CS mode as opposed to 50 that won’t kill the sale for me. Software can always be optimized in the future and they can send out upgrades to get a few extra MPG’s after the car is out. I would suspect that most people buying the Volt are in it for the first 40 miles without a case of range anxiety. If it isn’t the most fuel efficient car after 40 miles it’s not that big of a deal to me but I could see it being a problem for others. I’m pretty sure this is a good news day for John1701 but I’d still trade in the wife’s Prius for a Volt in a second.


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    Herm

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    Nov 23rd, 2009 (8:25 am)

    Gsned57: Sounds to me like he’s pretty much saying the Volt won’t be as efficient in CS mode as the Prius is

    SHE (Alex is a lady) did not say that.. she is basically saying that their main concern is not be the genset. That is a proper decision.

    If GM had been 100 percent focused on the genset they could have selected a diesel or some other fancy high efficiency engine, but that did not make economic sense.. those 40 miles that 80% of the public will actually use on a daily basis are the important ones.


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    LRGVProVolt

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    Nov 23rd, 2009 (8:25 am)

    #1

    Gsned57: If it isn’t the most fuel efficient car after 40 miles

    I believe her statement indicates that the Volt will have better MPG than the Prius which is the current leader in MPG. The specific part of her statement, I am referring to is this:

    “Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled.”

    I have long thought that approximately 60 MPG would be the final figure in CS mode. I concluded after reading the analysis discussion on this blog that my first thought on this topic was correct. From what Alex Cattelan says in this article, we may find out exactly what that figure is, very soon.

    Happy trails to you ’til we meet again.


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    ziv

     

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    Nov 23rd, 2009 (8:27 am)

    Alex is getting into the ‘how many angels can dance on the head of a pin’ arena in some of this, but I think she is saying that compromises were made and some people aren’t going to like them. Obviously they are compromising in favor of maximizing charge depleting performance, and it sounds like they will not get to 50 mpg in charge sustaining mode. But, as the chart shows, the ICE is not on half the time after you deplete the battery to 30%. You deplete to 30%, the ICE kicks in, you charge to 35%, the ICE shuts off and you are in all electric mode until you hit 30% again. Are you in charge sustaining mode if the car is operating in all electric mode at that point? Because if it isn’t technically charge sustaining mode in their engineer speak, then you could get 40 mpg in in charge sustaining mode, but since you are charging the battery to 35% and enabling the car to go into all electric mode for 4 miles or so… Which would in effect nearly double your apparent mileage. The chart does have a line that says the engine generator on = charge sustaining mode, ergo engine not on, not charge sustaining mode? Maybe so?
    OK, that is a whole lot of wishful speaking attempt to decode her engineer speak, but is it at all likely? I don’t think so, but I hope so.


  5. 5
    Herm

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    Nov 23rd, 2009 (8:33 am)

    LRGVProVolt: I believe his statement indicates that the Volt will have better MPG than the Prius which is the current leader in MPG. The specific part of his statement, I am referring to is this:
    “Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled.”

    Dont try to verbally pin down Alex, you will lose :)

    The Prius is not a conventional vehicle.. in any case GM may not release that number since its not really part of any established EPA testing procedures.. it may seem simple to us to measure gas consumption in CS mode but probably not to the statisticians at the EPA.

    The one thing we learned today is that the Volt will not work in discrete RPM steps like we all tought.. but instead will slowly change the rpm to suit the power generation demands.. at least until another GM boss pops up and says something else or even talks about a transmission like Lutz did.. but I think she did make a definitive statement.


  6. 6
    Randy

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    Nov 23rd, 2009 (8:33 am)

    (click to show comment)


  7. 7
    Tagamet

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    Nov 23rd, 2009 (8:35 am)

    I agree that between the lines it does sound like the goals are heavily weighted toward the first 40 miles and the extended range mileage is secondary to *performance* similar to that first 40 miles. Obviously, the higher the extended range mpg is, the better, but it’s not a deal breaker for me either (unless it is *really* “bad” – less than 35).
    Be well,
    Tagamet

    Let’s Just Get The Volts’ Wheels On The Road!!**********NPNS


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    BillR

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    Nov 23rd, 2009 (8:37 am)

    I summized about 10 days ago that the 2-mode could be used in the Volt as follows:

    ———————-
    After hearing how the Volt’s drive housing was similar to the 2-mode transmission, I started to do some research. It seem that the 2-mode uses a planetary gear set.

    http://en.wikipedia.org/wiki/Global_Hybrid_Cooperation

    More info is here:

    http://en.wikipedia.org/wiki/Planetary_gearset

    In the 2nd link, look at the gearset diagram in the upper RH corner of the page. The central gear in yellow is the sun gear. It meshs with the 4 planet gears shown in blue. The planet gears are held by the carrier in green, and the outer gear shown in red is the annulus.

    For pure EV mode, let’s assume the annulus is fixed, and the traction motor/generator (MG2) drives the sun gear. This is a reduction gear, and let’s assume a 2:1 ratio. So for every rev of the sun gear (direct connected to MG2), the output shaft (green carrier) turns 1/2 rev.

    A standard differential for the Corvette is a 2.56 final drive. So this equates to another speed reduction, combined equals 5.12. From one of my downloaded photos of the Volt, I could zoom in and read the tire size as P225/45R18. On the Michelin website, this tire rotates 802 rev/mile. Thus, in EV mode, MG2 would need to operate at 4100 rpm to drive the Volt at 60 mph (1 mile per minute).

    Now comes the interesting part. GM states that in some modes, the 2-mode is electronically variable. So now let’s image that the other motor/generator, the one driven by the ICE (MG1), is connected to the annulus. So as MG1 rotates the annulus, the gear ratio changes. If the annulus is rotated in the same direction and same speed as the sun gear, there is no rotation of the planet gears, and the speed reduction is 1:1. This means that MG2 now only needs to operate at 2050 rpm to drive the Volt at 60 mph.

    So by varying the relative speeds of MG1 and MG2, the gear ratio can be changed to put MG2 in its ideal operating zone.

    For charge sustaining mode, a clutch between the ICE and MG2 can be closed, and the ICE will now drive the gearset, and ultimately the wheels. Speeds of the MG’s can be adjusted so to provide the optimum speed from the ICE. At 45 mph steady level cruise, the ICE may be controlled to 1200 rpm, and the excess shaft power used to generate electricity for the battery pack. Go up a hill, and after a period of time, the ICE speed changes and power is taken from the battery to provide boost. I expect the ICE will operate at or near full throttle at all times, with its power output controlled by MG1 and MG2 by modulating its speed.

    So there is a possibility that gives the Volt an electronically variable speed transmission.
    —————————
    So let’s look at some quotes

    “All the primary propulsion is satisfied by the electric motor.”

    Does this imply that there is secondary propulsion, such as from the ICE or generator?

    “The engine is really there to supplement power to keep the battery sustained. Now there are a couple of tricks of the trade that we do since we have the engine on more, but for example we don’t want to do a whole lot of gearing that you would do in a parallel hybrid, because none of that is beneficial to you in the EV state.”

    Does this imply a geared connection from the ICE/generator to the wheels, however, its use is minimized?

    “We took all of the model that’s in the two mode hybrid and we’ve basically been carving out pieces we don’t need, adding in pieces we do need for this architecture and optimizing that model for this particular vehicle. We didn’t build this from scratch, this is also software that we are using that is also on the 2-mode but we are modifying it for optimizing this architecture.”

    Note that the 2-mode uses 2 – 60 kW MG’s embedded in the transmission. By limiting the ICE to 53 kW, GM can potentially use the one of these MG’s with little or no modification as the generator.

    This is an interesting topic, and I hope we get the chance to find out more.

    (Quote)


  9. 9
    MrDuck85

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    Nov 23rd, 2009 (8:37 am)

    She said: “Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled.”

    This implies to me that the CS mileage will be quite high, particularly keeping the point in mind that ziv made above. If the genset was capable of putting out a low enough power to maintain a steady city speed, it could stay on all the time in CS mode. I assume that in order to handle the highest output requirement (the mythical infinite hill) it was decided to cycle it for low-end needs. This makes sense with the buffer being provided by the battery.

    I’m looking forward to a very pleasant surprise when the actual CS mileage is announced. This will be a car whose mileage increases over the life of the car, simply due to ongoing software algorithm optimization.


  10. 10
    Tagamet

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    Nov 23rd, 2009 (8:39 am)

    Randy: GMs big seller is pickups and Suberbans,When will they work on an electric version of those. Razar has already put together a 100MPG electric hummer at reasonable cost with off the shelf parts. THey also plan to do the same with F150s,Silverados,Suberbans Ect.
    American runs on , The volt, while a worthy cause is just a people mover or a pizza delivery car,that will fight for a place in a crowded eco-box market. I guess you have to start somewhere,but GM should start with their strong sellers, not the segment where they are already getting creamed by the competition.  

    There’s a strong argument for converting existing guzzlers rather than the smaller cars, because the gas savings are greater. I doubt, however, that the EREV *at this point* is ready battery-wise for large vehicles. Once the battery cost comes down, they’ll be all set. JMO.
    Be well,
    Tagamet

    Let’s Just Get The Volts’ Wheels On The Road!!**********NPNS


  11. 11
    Dan Petit

     

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    Nov 23rd, 2009 (8:40 am)

    Nice descriptive flow in Alex’s interview. Her explanations really get to the basics for the philosophy of Volt. Eleven or so more months, and perhaps we can have individual owners describing also what Alex knows and describes for us all so well.


  12. 12
    George S. Bower

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    Nov 23rd, 2009 (8:40 am)

    So, as we suspected, they are programing the ICE to run on a line of peak efficiency on the ICE performance map. The other point of the article is that they are using 2 mode tranny SOFTWARE and no mention of couplings or mechanical transmitions. The Volt should be able to equal the Prius in CSM MPG. It has an almost 10% advantage in the aero drag department.


  13. 13
    Randy

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    Nov 23rd, 2009 (8:41 am)

    GM already admits there is little or no profit in small cars,even less in reasearch intrensive ones. ANy company will not survive for long without profit. FIx the BIG problem first the 10-12MPG guzzlers that make up 50+ % of the market and use all the gas. THe prius size cars are not the problem with oil shortage.


  14. 14
    Herm

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    Nov 23rd, 2009 (8:46 am)

    BillR: “All the primary propulsion is satisfied by the electric motor.”
    Does this imply that there is secondary propulsion, such as from the ICE or generator?

    NO.. it says ALL that drives the wheels is the motor. Very clear statement.

    Its not 100% correct since there is some forward thrust from the radiator fan and the exhaust (if the pipe is aimed to the rear), if you want to be picky about it.

    note: “We’re tuning our fuel economy right now.”

    They may simply not know what the CS Mode mpg is yet.


  15. 15
    Tagamet

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    Nov 23rd, 2009 (8:47 am)

    BillR
    It’s my understanding that there is no physical connection between the ICE and the wheels. It’s all electric all the time. Am I wrong on that?
    Thanks.
    Be well,
    Tagamet

    Let’s Just Get The Volts’ Wheels On The Road!!**********NPNS


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    Jason M. Hendler

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    Nov 23rd, 2009 (8:53 am)

    Certainly, the more EV miles they deliver, the better overall fuel economy – hopefully no fuel at all.

    Less than 12 months away now …


  17. 17
    George S. Bower

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    Nov 23rd, 2009 (9:01 am)

    to BillR:
    I just don’t think this article implies that GM is using MECHANICAL parts of the 2 mode tranny, just 2 mode tranny SOFTWARE.


  18. 18
    Jackson

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    Nov 23rd, 2009 (9:10 am)

    On the one hand:

    “We like to think of it not as a hybrid. You’ve got to understand that all of the decisions that we’ve made around this product are made because its an EV. That is the first and foremost thing that it needs to be. So because it is an EV some of the decisions that we’ve made around engine operation will be different than what Toyota makes in its parallel hybrid.”

    But on the other hand:

    “So think of it as the beauty of being able to decouple the engine is we have a degree if freedom that we don’t have to follow the pedal at all. We can pick and choose the points that are most efficient, we can go between those point on the best path and the most pleasing path to the customer”

    Net result:

    We still don’t know what true mpg in CS mode will be!

    While I remain optimistic (50+ mpg), I think GM should, when most advantageous for advertising, reveal this true CS mpg figure; and not wait for someone on this site (probably Lyle) to purchase an actual Volt and perform the test in terms of a set distance on a depleted battery, noting the actual usage of gasoline. This constant dancing around details on the matter makes it look like GM is hiding something; and mostly to it’s detriment in the EV PR sphere.

    BillR: For charge sustaining mode, a clutch between the ICE and MG2 can be closed, and the ICE will now drive the gearset, and ultimately the wheels.

    The insistance that the engine must power the wheels at some point comes up now whenever CS mode is discussed; it is starting to sound like a conspiracy theory.

    Perhaps we should ask BillR who really shot Kennedy? ;-)


  19. 19
    kdawg

     

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    Nov 23rd, 2009 (9:26 am)

    After Alex’s comments, i’d estimate 35-40mpg is probably pretty close in CS mode. I like the way she deflects attention given to this number by reaffirming the first 40 miles of EV driving is what counts. Getting better mpg in CS mode than a Prius or a Focus may have been nice bragging rights, but when you factor in the EV part of the trip you start getting 100~200mpg in a Volt anyway.

    GM needs to add a scale to the left side of the chart. I’d like to know the deadband in CS mode.


  20. 20
    BillR

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    Nov 23rd, 2009 (9:27 am)

    Herm:

    BillR: “All the primary propulsion is satisfied by the electric motor.”Does this imply that there is secondary propulsion, such as from the ICE or generator?

    NO.. it says ALL that drives the wheels is the motor. Very clear statement.
    Its not 100% correct since there is some forward thrust from theradiator fan and the exhaust (if the pipe is aimed to the rear), if youwant to be picky about it.
    note: “We’re tuning our fuel economy right now.”
    They may simply not know what the CS Mode mpg is yet.  

    Then why the word “primary”? Why not just state “All the propulsion is satisfied by the electric motor.”?


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    Green Washing

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    Nov 23rd, 2009 (9:28 am)

    (click to show comment)


  22. 22
    BillR

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    Nov 23rd, 2009 (9:41 am)

    Tagamet:
    BillRIt’s my understanding that there is no physical connection between theICE and the wheels. It’s all electric all the time. Am I wrong on that?Thanks.Be well,Tagamet
    Let’s Just Get The Volts’ Wheels On The Road!!**********NPNS   

    Tag,

    This is what we thought since 2007. However, Bob Lutz has hinted at a “secret transmission”, and someone from GM mentioned in an online chat that it was “darn deliberate” that the Volt’s MG housing looked similar to the FWD 2-mode.

    Alex also mentioned in a prior interview that she had some method to use the generator in a mode to help the traction motor operate in its most efficient band.

    http://gm-volt.com/2009/11/09/engineering-design-of-the-chevy-volts-two-electric-motors/

    One of her quotes,

    “We do have the ability to utilize both motors in propulsion mode.”

    I don’t profess to have the answer, but have only offered a possibility that uses both motors in propulsion mode, uses something similar to the 2-mode transmission, and provides a variable speed drive for the traction motor.


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    carcus1

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    Nov 23rd, 2009 (10:01 am)

    On mpg:
    Several times in the conversation (when approached on the subject) she redirects and emphasizes that they are focusing on EV performance, and says that it will get better than conventional mpg. That, to me, sounds like mpg is going to be better than a conventional car but not as good as a regular hybrid.

    On volt design — series vs. series/parallel:

    Still not clear. Her use of that “coupling” word (again) gets a little confusing. Especially where she says “being able to decouple” . . . ., but this interview doesn’t lend itself to the “mechanical conspiracy” nearly as much as the one posted on 11/9/09.

    / I think 50+ mpg is sounding more and more like a conspiracy


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    Guido

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    Nov 23rd, 2009 (10:05 am)

    Green Washing: This is purely for PR purpose, I also feel they are dancing around the details w/o revealing anything, they are not honest company:
    1). MPG during CS mode.
    2). Degradation of the battery
    Everyone here will be disappointed eventually!

    ———–
    So sorry for your miserable life ! Now, back under the bridge with you!


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    mikeinatl.

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    Nov 23rd, 2009 (10:07 am)

    I dont think GM is being secretive about the mileage in CS mode. I don’t think they know yet.

    In fact, it’s not possible to know what the mileage in CS mode will be at this point. GM is still trying to find the best balance for when and how the ICE comes on.

    First, provide that 40 mile EV range.

    Next, make sure the CS mode provides all power needed to sustain operation in all possible environments.

    Then, optimize for the driver experience so that there is a minimum of engine noise and sensation as the ICE sustains the battery’s charge.

    That last step seems to be where much of their focus is now. And the more they have to “feather-in” the ICE to reduce noise and other sensation, the more fuel it uses, lowering the gas mileage.

    So they don’t yet know what the mileage will be in CS mode. And when they do, THEN they might be secretive about it for marketing purposes, but not yet.


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    George S. Bower

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    Nov 23rd, 2009 (10:19 am)

    Not putting in a complex tranny is about COST. Even though it would make the CSM MPG better, the volt is already so expensive it’s just not an economically sound decision.


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    nasaman

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    Nov 23rd, 2009 (10:26 am)

    I find this interview to be fascinating. I have long believed the FWD 2-mode transmission (which included two 75HP electric motors in the version used for the original plug-in Saturn VUE) could be fairly easily modified to meet both the Volt’s generator & drive motor requirements ….by removing unneeded gearing and clutches, scaling up the motor used for traction and optimizing the motor used as the CS generator. As with the 2-mode, the motor & generator are sealed in a housing bolted to the ICE and are oil cooled. I would guess that the housing itself may need only minor changes. And we now learn that parts of the 2-mode software code will also be adapted to the Volt requirements —excellent!


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    Flaninacupboard

     

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    Nov 23rd, 2009 (10:27 am)

    I guess you American chaps won’t see it just yet, but the guys made a series hybrid on Top Gear last night, and they’d mocked up an Autocar review, describing it as “Britains answer to the Volt!”. It was powered by a 12kw milkfloat motor, and used a diesel generator for power. Quite interesting, if a little childish what they did with it.


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    srschrier

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    Nov 23rd, 2009 (10:33 am)

    The less aerodynamic new Chevy Cruze which is said to be built on the same platform as the Volt reportedly is getting low 40s highway MPG using the same four cylinder engine that serves as a generator for the Volt, though there may be a difference in each vehicle’s weight.


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    Ray

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    Nov 23rd, 2009 (10:33 am)

    Not knowing the exact details of the EV propulsion system in the Volt… I can tell you that to be in just the EV Mode on my 2010 Fusion Hybrid….
    you can get up to 73 KPH (40 MPH) on strictly electric and on level “coasting at speed” up to 77 KPH.

    However… to accelerate up to that speed ( in EV Mode)… you have to drive the car as if it were a large tractor trailer unit with a full load…
    On a clear stretch of road with no traffic… it could take up to a KM (1/2 a mile) to get up to 70 KPH..

    This car is not the fastest on the block for getting up to speed…. but by using the ICE in conjunction with the electric motor.. you can easily get up to the posted speed limits and …. once there…
    a light foot on the pedal will keep you in EV Mode for varying distances..
    The longest distance acheived so far…..well over 10 KMs ( 6 miles ) in EV mode. It all depends on the relative speed of the surrounding traffic, traffic conditions, road grade … etc..
    I have over 10,000 KMS on the car so far and the life time average milage is 5.8 L / 100 KMS (40.5 MPG US)
    Still loving the car…..and waiting for the Volt as a second car…


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    GM Volt Fan

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    Nov 23rd, 2009 (10:33 am)

    It sounds like the algorithms for charge sustaining mode operations are going to be a wee bit complex. I bet they will end up with equations that look like something Einstein would use. Lots of variables will need to be juggled in order to optimize everything.

    Plenty of control software programming and tweaking too. Let’s hope that GM has some really good programmers and scientists on the Volt design team. Hopefully, everything will be heavily tested, debugged, benchmarked, and super robust by the time the Volt hits showroom floors.


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    Nov 23rd, 2009 (10:43 am)

    My speculation is that the CS mode MPG is highly dependent on mode of operation. From the comments from Alex concerning the decoupling of the engine and the axle, it is apparent that the Volt system will be more efficient in city driving (when compared to the Prius and conventional), but will NOT be as efficient in long distance high speed driving. This is true of the Pruis also, but the differences between city and highway MPG may be more amplified for the Volt.

    So if you live in a city with poor traffic light management (like me), and you end up hitting every single red light going to and from work, then the Volt is for you…even if you drive exclusively in CS mode :)


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    Nov 23rd, 2009 (10:48 am)

    LRGVProVolt: Gsned

    LRGVProVolt, I read below and my eyes stuck to the more efficieint than a conventional vehicle.

    “Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled. Again were optimizing some of those efficiency point puts we are really doing is focusing on the optimization of the EV. There are trade offs because we absolutely consider this product an EV by nature.”

    Personally I too thought the Volt getting 50 MPG in CS Mode was understated but since she didn’t outright say better MPG than any car curently on the market instead saying better than conventional vehicles to me means it won’t be as high as the Prius.


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    Joel

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    Nov 23rd, 2009 (10:51 am)

    I fail to get too excited about these new technologoes for electric vehicles when we had a battery 12 years ago that could go 5 times as far. The NiMH battery (mothballed by Chevron) powered the Saturn EV-1 and the Toyota RAV-4 EV which were both 100% electric, not hybrid cars. GM crushed the EV1s but the RAV4s that were sold are still on the road in California. We could get the battery technology back from Chevron, Cefo, the author of Two Cents Per Mile, argues. If I could buy an electric car that got 200 mile sper charge, I would be sitting here typing. I’d be out buying it!


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    Nov 23rd, 2009 (10:51 am)

    Herm: Gsned57: Sounds to me like he’s pretty much saying the Volt won’t be as efficient in CS mode as the Prius is

    SHE (Alex is a lady) did not say that.. she is basically saying that their main concern is not be the genset. That is a proper decision.

    If GM had been 100 percent focused on the genset they could have selected a diesel or some other fancy high efficiency engine, but that did not make economic sense.. those 40 miles that 80% of the public will actually use on a daily basis are the important ones.

    Herm, I think you misread my first post. “Even still I agree that their focus must be on the first 40 miles and if the Volt only gets 40MPG in CS mode as opposed to 50 that won’t kill the sale for me”. I


  36. 36
    Texas

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    Nov 23rd, 2009 (10:52 am)

    1) I wonder about that marketing approach; the Volt is an EV and thus is not optimized for CS mode. It’s going to be far too complicated for the average consumer. Additionally, I don’t buy it. Sorry, but if the engine is not following the power needs in CS mode on the highway then the efficiency is going to drop even more (wasting energy storing to the battery (more steps away from ICE – to – Wheels).

    2) Why not just say the Volt is more geared for city drivers. It’s an EV that you don’t have to worry about having range anxiety. Say the Volt will work like a very efficient normal car on the highway (just not exceptionally great).

    3) My gut feeling is that in the end the ICE will follow the pedal. Playing around with different combinations will not lead to a noticeable gain and it will only make a “disconcerting” feeling. Of course, for us nuts, please give us that super efficiency mode as a selectable mode. Not only don’t we care that the ICE acts strangely, we like it! :)

    Keep up the great work GM. Just don’t kill yourselves trying to justify your decision to go serial hybrid. Yes, it will not be as good on the highway but it will be amazing 80% of the time when in the city! I can’t wait to tool around the block.

    Drive the highway? Get a diesel. For the rest, the Volt is best!


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    Nov 23rd, 2009 (10:54 am)

    BillR: “We do have the ability to utilize both motors in propulsion mode.”
    I don’t profess to have the answer, but have only offered a possibility that uses both motors in propulsion mode, uses something similar to the 2-mode transmission, and provides a variable speed drive for the traction motor.

    This whole thing about using gears and clutches is old school thinking. I am thinking that they are talking about using electronic/electrical optimization between the generator and the traction motor.

    I doubt that they would use mechanical connection between the genset (either generator or ICE) to the wheels as this would cause the cost to increase and the other issues (vibration, harshness, etc.) to be harder to solve.

    Around July 2010, they will have EPA evaluation and real production cars out there for journalist testing. We will know way before 11months from now how all these things (cs mode mileage, genset operation, etc.) will shake out.

    Even if pure cs mode mileage is terrible (~30mpg) the overall AVERAGE mileage will still blow last generation hybrids out of the water. I believe the EPA sticker will say 115/230 (hwy/cty) and that will be enough to make the case.

    I’m still amazed that the EPA would use ‘gas mileage’ to evaluate an electric car, but, that’s the way game-changing technology works. You can’t use the old paradigm anymore. ‘Your mileage may vary’ takes on a whole new meaning at 600mpg. (42 mile total commute. calculate it out!)


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    Nov 23rd, 2009 (11:08 am)

    I’ll leave the technological speculation to BillR and nasaman since this stuff is way beyond me. (They may be reading more into some of the comments than is there — people sometimes just aren’t 100% precise). However, it does seem that Carcus1 is right — from the way she handled the question about the mpg in CS mode it seems that she’s explaining why we’re not going to see the 50 mpg numbers we saw from the simulation.

    So the actual number will be less than 50 mpg. We just don’t know how much less. I was reasonably confident that GM would hit a low 40 mpg but maybe that’s a little too high. We know it will be better than a conventional vehicle, which would probably get mpg in the high 20s during the City and low 30s during Highway. I’m just not sure by how much. So somewhere between high 30s and low 40s? Just a guess.

    FWIW mpg in CS mode is not that important a factor to me. Given that the Volt, like all EVs, is a commuter car, the range extender is more a range anxiety killer than a mode you want to drive in. Like some forms of insurance, it’s just great to have even though you never really want to use it.


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    Anthony M. O'Neil

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    Nov 23rd, 2009 (11:08 am)

    I have been wondering what the status of work within GM to use Super Capacitors like AFS Trinity to help take the load off of the Lithium Batteries.
    It seems to me that Super Capacitors would help the Volt Power System as well as the Two Mode Hybred Power System.


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    Nov 23rd, 2009 (11:11 am)

    Joel: If I could buy an electric car that got 200 mile sper charge, I would be sitting here typing. I’d be out buying it!

    You can. It’s called a Tesla. The EV1 also cost about 100grand which is why they were leased.


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    Nov 23rd, 2009 (11:12 am)

    Loboc:
    I’m still amazed that the EPA would use ‘gas mileage’ to evaluate an electric car, but, that’s the way game-changing technology works.   

    The EPA has to use mpg because of CAFE. It doesn’t have a choice from a legal point of view. However, from a consumer standpoint, cost of operation would be a much better approach. Edmunds has actually done this for us:

    http://www.edmunds.com/industry-car-news/fuel-mileage-equivalency.html


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    Nov 23rd, 2009 (11:32 am)

    kdawg: GM needs to add a scale to the left side of the chart. I’d like to know the deadband in CS mode.  

    Why?.. I would love to know it also but I bet that is one of the things they are working on right now, probably very valuable corporate info.
    It will take GM’s competitors a few months to reverse engineer these settings, and that is after they get their hands on a Volt in early 2011. Its economic warfare.
    We would like it if GM optimized the genset for best CS Mode mileage, but they first have to give the customer a pleasing experience and then they have to satisfy CARB and the EPA.. too many shackles on the engineers.


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    Nov 23rd, 2009 (11:34 am)

    What Alex said made perfect sense to me, the Volt is a serial hybrid and they are optimizing EV efficiency, which I define as Miles Per KWh (MPKWh). That’s exactly what they should do, optimize the MPKWh, as the Volt’s EV efficiency will play a major role in the Volt’s MPG during charge sustaining mode. They also need to optimize the generator efficiency, which I would also group under EV efficiency.

    Since the ICE is not coupled to the wheels, they are free to operate in the engine sweet spots (most efficient operation), which is what she stated they are trying to do while also attempting to minimize NVH . Otto engines have a peak efficiency of about 35% – in other words, 35% of the energy generated by combustion is converted into useful rotational energy at the output shaft of the engine, while the remainder appears as waste heat.

    Electric generator losses usually include copper losses in the winding and magnetizing losses in the core, plus rotational losses. Generator efficiencies can range from 93-97%.

    For example, 1 Gallon of Gas is equal to approximately 36.4 kWh, and if the Volt’s EV efficiency at a constant 70 MPH is 3.5 MPKWh; and

    ICE efficiency = 35%
    Generator Efficiency = 95% (electricity to the battery)

    The Volt charge sustaining MPG would be:

    36.4 (KWh/Gallon) x 3.5 (Miles/KWh) x 35% x 95% = 42.4 MPG.

    A higher EV efficiency (MPKWh) directly translates in a higher charge sustaining MPG, all things being equal.


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    Nov 23rd, 2009 (11:49 am)

    I hear that some new “vanadium” batteries may be on the way soon and that they have longer life and a lot more power. Can anyone who knows about them comment.


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    LRGVProVolt

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    Nov 23rd, 2009 (11:50 am)

    #7

    Tagamet: I agree that between the lines it does sound like the goals are heavily weighted toward the first 40 miles and the extended range mileage is secondary to *performance* similar to that first 40 miles. Obviously, the higher the extended range mpg is, the better, but it’s not a deal breaker for me either (unless it is *really* “bad” – less than 35).
    Be well,
    TagametLet’s Just Get The Volts’ Wheels On The Road!!**********NPNS   

    Alex is telling us what the design requires for an EREV as apposed to the ICE. This is not engineering speak as ziv states: it is plan English for the differences between the two types of propulsion. Since the Volt is a vehicle that has no transmission or gear box, the electric motor must be their primary concern with regard to efficiency. The Volt will be far more efficient than any ICE vehicle or hybrids like the Prius since it has no mechanical link to the wheels.

    And unlike others who think I am second guessing here. Herm, I am merely taking what she said; it seems simple and clear. How anyone can read more into her statement is beyond me. Alex realizes that many people will read Lyle’s report here and therefore spoke in plain English. We can correctly interpret it as meaning that the ICE range extended will be more efficient than the normal ICE vehicle engine since the range extender runs in a sweat spot range most of the time unlike the ICE vehicles engine. Additionally, the battery pack acts as a buffer providing additional electricity to augment that produced by the generator. Therefore, in CS mode when the engine/generator is running, it will be much more efficient than an ICE vehicle engine.

    Tagamet, consider what GM plans to do with the Converj in the U.S. market. They are stating that it should get over 40 MPG, and we are talking about a transmission driven ICE vehicle. I don’t believe the Volt’s ICE will get less or any where around 35 MPG and although I agree with you on this, my belief is stronger that it will not be this bad. It’s efficiency will allow much better MPG. IMHO, it will get better than the 55 MPG or so that the Prius gets. From what we see of the component configuration and the information we have been given on performance so far, we should expect to see MPG for the Volt around 60 MPG. This is my estimate an I’ll stand by it.

    Happy trails to you ’til we meet again


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    Nov 23rd, 2009 (11:50 am)

    Lyle,

    Could you clear up the “mechanical conspiracy” with a simple question to an official GM source next time you talk:

    “Is the ICE ever mechanically coupled to the Volt’s drive train?”

    Thanks.

    /After re-reading Cattelan’s comments, It still seems to me that she’s talking about a modified 2 mode — i.e. series/parallel configuration — but different from the prius in that they can totally “decouple” the electric side of the drive train from the planetary gear set that links mechanically (sometimes) in order to maximize EV mode efficiency. All her comments make more sense to me when I read it this way.


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    Nov 23rd, 2009 (11:58 am)

    BillR: Tag,This is what we thought since 2007. However, Bob Lutz has hinted at a “secret transmission”, and someone from GM mentioned in an online chat that it was “darn deliberate” that the Volt’s MG housing looked similar to the FWD 2-mode. Alex also mentioned in a prior interview that she had some method to use the generator in a mode to help the traction motor operate in its most efficient band.nbsp; (Quote)

    Why wouldn’t she simply be referring to running the generator and electric motor in phase?


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    Nov 23rd, 2009 (11:58 am)

    #46 add,

    // What would this configuration be called . . . series–series/parallel? ;)


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    Nov 23rd, 2009 (12:03 pm)

    You guys are so interesting! Much speculation. But may I direct your attention to this. This is the first production EV from GM. They make more profit from big vehicles. This is just a test for things to come. There might be a 2-mode transmission in the future. There might be hydrogen fuel cells. There might even be different kinds of ICE. But the ARCHITECTURE had better be there to support all of it or it WILL be just an expensive science experiment. I for one think it is much more than that. It looks like it has the ability to support many configurations.


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    LRGVProVolt

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    Nov 23rd, 2009 (12:06 pm)

    #20

    BillR: Then why the word “primary”? Why not just state “All the propulsion is satisfied by the electric motor.”?

    Could be that, since the Volt has both an electric motor and an internal combustion engine, the word “primary” is used to eliminate any confusion by the uneducated reader.

    Happy trails to you ’til we meet again.


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    CaptJackSparrow

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    Nov 23rd, 2009 (12:08 pm)

    Back to life after that friggin H1N1 Swine Flu.

    Graph looks pretty and all but there are no numeric metrics. Means nothing to me other than a graphical illustration of a theoretical principle of operation.

    There’s still almost a year left for them to tweak. So nothing new.


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    Nov 23rd, 2009 (12:13 pm)

    #21

    Green Washing: While I remain optimistic (50+ mpg), I think GM should, when most advantageous for advertising, reveal this true CS mpg figure; and not wait for someone on this site (probably Lyle) to purchase an actual Volt and perform the test in terms of a set distance on a depleted battery, noting the actual usage of gasoline. This constant dancing around details on the matter makes it look like GM is hiding something; and mostly to it’s detriment in the EV PR sphere.>>>>>> This is purely for PR purpose, I also feel they are dancing around the details w/o revealing anything, they are not honest company:
    1). MPG during CS mode.
    2). Degradationof the batteryEveryone here will be disappointed eventually!  

    It is more likely you will be the one disappointed and perhaps a bit embarrassed when you find out have wrong you are.

    Happy trails to you ’til we meet again.

    P.S. The survival of GM is important to the livelihood of all their employees and those of companies supplying them parts and those who retail their vehicles. As one of the last remaining manufacturing corporations in the U.S., they are vital to a healthy American economy and most likely the sustained existence of your job.


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    Nov 23rd, 2009 (12:19 pm)

    Last year we had a thread which looked at the cooling and pump systems to be used in the Volt. Although GM wasn’t 100% specific. The “T” battery temperature control pump sounds like an enclosed impeller driven by an exterior (uncoupled) magnet.
    I can see the main ICE generator on the Volt being hard bolted to a primary drive spindle. With the booster/make-up motor being an opportunity user of any excess power the ICE delivers to the generator spindle.
    It doesn’t cost anything to harvest this freewheeling energy. As the process is part of the braking system. This magnetic vampirisation is consistent with the “no stone left unturned” approach mentioned by GM engineering.

    If this is the case. We now understand why GM is holding back on the CS mpg number. Because it will vary greatly with terrain and driver aggressiveness. And because magnetic opportunity reclaim will take months to fine tune. “Sport” mode is simply a command for higher magnetic attraction. Or possibly the actuation of magnetic post proximity through mechanical means. A little more E85 per mile is needed to have the battery prepped and ready to use 100% on demand torque. A simple idea spawned from the EREV dream.

    =D~


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    Nov 23rd, 2009 (12:22 pm)

    Jackson: This constant dancing around details on the matter makes it look like GM is hiding something; and mostly to it’s detriment in the EV PR sphere.

    #18

    Alas, I have to agree with that.


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    Nov 23rd, 2009 (12:26 pm)

    BillR: Then why the word “primary”? Why not just state “All the propulsion is satisfied by the electric motor.”?

    A perfectly logical question, IMHO. +1


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    Nov 23rd, 2009 (12:27 pm)

    kdawg: GM needs to add a scale to the left side of the chart. I’d like to know the deadband in CS mode.

    There is a scale on the left. It says 100% at the top, and seems to be linear. Extrapolating with a ruler held to my screen, it appears that the battery hits “full charge” at about 90-95% of capacity, it hits “discharge” at about 30%, the CS band ranges from 30 – 40%, with an “ideal” SOC of about 35%. This is fully in keeping with everything else I’ve read here and elsewhere.


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    Nov 23rd, 2009 (12:27 pm)

    That the CS mode has the responsive flexibility of charge & generator Alex outlines advances a point of question. I have tiered billing like most of the U.S. Even lowest use months I’m pushing into the third tier at .1829/kWh. Since my regular use crosses every month into the third tier EV use will ALWAYS be in the third tier. Thus, the cost of an 8 hr 120 VAC charge is about $1.47/kWh. One could argue 80 miles per gal. Whereas CS mode mileage works out around 50 mpg the diff is approx. 2/3rds of a gal. or $2. Therefore, if the driver were given an option to charge wholly in CS mode the cost diff is the charge time to 80% x $2. (at 53 kWhs minus applied drive power) would easily be within 2 hrs. – My question is: why not give the driver the option of charging the battery even though mileage is off optimum? The corollary point being: We start with EVM; CSM + charge to 80% (per driver optional selection); [back to] EVM –


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    Nov 23rd, 2009 (12:28 pm)

    Contrary to some opinions posted above, I don’t believe that the Volt will achieve superb mileage (50-60MPG) while in range extended mode. Chevy has been selectively disclosing information to the press about the Volt, and the fact that gas mileage while in RE mode – and even fuel tank capacity – are still big secrets tells me that it is not something they want to disclose until they absolutely have to.

    Personally, I think that the RE mileage will fall somewhere in the mid 30s. I hope I’m wrong.


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    Nov 23rd, 2009 (12:28 pm)

    $26

    George S. Bower: Not putting in a complex tranny is about COST. Even though it would make the CSM MPG better, the volt is already so expensiveit’s just not an economically sound decision.  

    Right on!!! Just one more reason to end this topic from discussion and get on with it. The statements about gearing for the Volt is an interesting subject but much more likely with regard to trucks and light duty vehicles.

    Happy trails to you ’til we meet again.


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    Nov 23rd, 2009 (12:30 pm)

    CaptJackSparrow: Back to life after that friggin H1N1 Swine Flu.Graph looks pretty and all but there are no numeric metrics. Means nothing to me other than a graphical illustration of a theoretical principle of operation.There’s still almost a year left for them to tweak. So nothing new.  

    Welcome back!
    One little detail I noticed is that the SOC is never 100% even when parked. Is that a typo or is that really true? Just curious.


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    Nov 23rd, 2009 (12:33 pm)

    Texas: Of course, for us nuts, please give us that super efficiency mode as a selectable mode. Not only don’t we care that the ICE acts strangely, we like it!

    #36

    Right.


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    Nov 23rd, 2009 (12:36 pm)

    V=IR: One little detail I noticed is that the SOC is never 100% even when parked. Is that a typo or is that really true? Just curious.

    I think they were talking about the “REAL” SOC where max charge will be ~85%? If that’s the case then yeah, the user defined 100% SOC is actually ~85% and saying it will not never be 100% is correct.


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    Nov 23rd, 2009 (12:38 pm)

    #33

    Gsned57:
    LRGVProVolt,I read below and my eyes stuck to the more efficieint than a conventional vehicle.“Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled. Again were optimizing some of those efficiency point puts we are really doing is focusing on the optimization of the EV. There are trade offs because we absolutely consider this product an EV by nature.”Personally I too thought the Volt getting 50 MPG in CS Mode was understated but since she didn’t outright say better MPG than any car curently on the market instead saying better than conventional vehicles to me means it won’t be as high as the Prius.  

    Conventional = ICE + Hybrids
    Non-conventional = Volt + other EV’s

    Time will tell!

    Happy trails to you ’til we meet again.


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    Nov 23rd, 2009 (12:52 pm)

    MrDuck85:
    There is a scale on the left.It says 100% at the top, and seems to be linear.Extrapolating with a ruler held to my screen, it appears that the battery hits “full charge” at about 90-95% of capacity, it hits “discharge” at about 30%, the CS band ranges from 30 – 40%, with an “ideal” SOC of about 35%.This is fully in keeping with everything else I’ve read here and elsewhere.  

    It is interesting that the first time SOC hits the yellow line it charges back up to ideal level. After that it only charges back up once it hits the red.


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    Dave K.

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    Nov 23rd, 2009 (1:05 pm)

    coffeetime: I think that the RE mileage will fall somewhere in the mid 30s.

    There has been much mention of ICE noise while in CS mode. There are two cures. Make the ICE quieter with a smothering exhaust system. Or use a quieter design such as a rotary engine. At face value the rotary engine sounds like a match made in heaven. Wankles operate with more of an electric buzz than a bang bang bang piston sound. And run very smooth.
    But, both the conventional ICE with smothering exhaust and the smooth rotary engine result in low mpg. Simply not efficient.

    Since GM is focusing on EV range with their engineering trade offs. I expect the convention ICE extended range engine to be audible yet smooth sounding to the ear. CS mpg being “better than conventional vehicles” means 40mpg+. I expect “sport” mode to deliver battery/CS numbers of 35/40. With “standard” mode delivering 40/45. And up to 45/50 for Sunday afternoon drivers.

    =D~


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    Nov 23rd, 2009 (1:08 pm)

    Dave K.: I expect “sport” mode to deliver battery/CS numbers of 35/40. With “standard” mode delivering 40/45. And up to 45/50 for Sunday afternoon drivers.

    I can live with that!


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    LRGVProVolt

     

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    Nov 23rd, 2009 (1:09 pm)

    #51

    CaptJackSparrow: Back to life after that friggin H1N1 Swine Flu.Graph looks pretty and all but there are no numeric metrics. Means nothing to me other than a graphical illustration of a theoretical principle of operation.There’s still almost a year left for them to tweak. So nothing new.  

    It may be old hat to most of the readers here, maybe not, but for those who are new it does explain how the Volt works during each type of mode. I do think it is neat to see the slight blips in remaining charge with regeneration working during Electric Vehicle Mode, the horizontal lines showing when Extended Range Mode which I am assuming are at 35% SOC, 30% SOC, and 25% SOC, with the statement the engine will be on/off at certain times, and the upper charge limit of 80% SOC. If my assumptions are correct, the SOC will never drop below 25% SOC. And when the motor/generator put electricity back into the battery giving 35% SOC, the motor/generator will turn off and all electric drive will resume. All in all, the chart clearly explains much of what we need to know about how the Volt operates without us ever getting into the vehicle and driving it.

    Happy trails to you ’til we meet again.


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    LRGVProVolt

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    Nov 23rd, 2009 (1:18 pm)

    coffeetime: Contrary to some opinions posted above, I don’t believe that the Volt will achieve superb mileage (50-60MPG) while in range extended mode.Chevy has been selectively disclosing information to the press about the Volt, and the fact that gas mileage while in RE mode – and even fuel tank capacity – are still big secrets tells me that it is not something they want to disclose until they absolutely have to.Personally, I think that the RE mileage will fall somewhere in the mid 30s.I hope I’m wrong.  

    Why would you think of mid 30,s which is typical for a transmission ICE vehicle and current engines are coming that get better than 40? This idea that GM is committing a conspiracy is non-sense at this point. GM is in the final phase of tweaking the efficiency of the ICE motor/ generator extender. Until they finalize that there is no reason to give out what might to termed misinformation.

    Happy trails to you ’til we meet again.


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    Nov 23rd, 2009 (1:42 pm)

    Rooster:

    BillR:Tag,This is what we thought since 2007. However, Bob Lutz has hinted ata “secret transmission”, and someone from GM mentioned in an onlinechat that it was “darn deliberate” that the Volt’s MG housing lookedsimilar to the FWD 2-mode. Alex also mentioned in a prior interviewthat she had some method to use the generator in a mode to help thetraction motor operate in its most efficient band.nbsp; (Quote)

    Why wouldn’t she simply be referring to running the generator and electric motor in phase?  

    From my interpretation of the articles on this subject, both the traction motor and generator can drive the vehicle (to some extent) or either can act as a generator.

    With a completely mechanically disconnected system, the ICE drives the generator, and the traction motor drives the wheels through a differential (gear reduction). This leaves no method that I know of to change the traction motor speed relative to wheel speed. The EV1 was configured in this way.

    http://www.eanet.com/ev1-club/evpics.htm

    http://www.evchargernews.com/CD-A/gm_ev1_web_site/features/features.htm

    For the Volt in EV mode, the electric coupling of the two MG’s could be beneficial by splitting the high amperage between the units. However, in CS mode, this would not be practical very often as it would require the two to run at the same speed, and it would be hard to link ICE speed with vehicle (wheel) speed.

    Finally, this method provides no means of varying the MG speed vs. wheel speed, so perhaps there is no “secret transmission”. As others have stated, now the ICE drives the generator, and this power must now go to the power electronics to provide the proper frequency and voltage for the traction motor. There are inherent losses with this conversion.

    With the 2-mode arrangement, you can vary the effective gear ratio, get more flexibility in the operation between each MG, and eliminate some of the losses associated with converting AC power from the genset to DC power and then back to AC power at the proper frequency and voltage.

    So that’s my reasoning.


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    Nov 23rd, 2009 (1:43 pm)

    LRGVProVolt: GM is in the final phase of tweaking the efficiency of the ICE motor/ generator extender. Until they finalize that there is no reason to give out what might to termed misinformation.

    If we can breathe so much into anything said about CS mode here, imagine how GM would be absolutely crucified over a 5% difference between today’s estimate and what is sold in dealerships.

    My concern is that GM will continue to hedge and look bad once they know the figure, for reasons unrelated to engineering. I think that they may be tempted to do this for marketing reasons, or to try and divorce the concept of mpg in CS mode from arguments which take into account overall efficiency (including AER miles).

    Sooner or later, this CS-mode, battery-depleted mpg metric will become known to early adopters through direct experience, and will be made public on the Internet. IMHO I believe it will benefit GM long term to “come clean”/”spring the surprise” earlier rather than later.

    I find it very hard to believe that CS mode will be only able to achieve “mid-thirties,” and that worst case will be that it only beats the Ford Focus hybrid and not the Prius.

    I’m not an automotive engineer. My only real qualification where EREV and EVs are concerned is having thought about the subject for 40+ years, for whatever that’s worth. I’ve imagined vehicles based solely on the idea behind CS-mode (able to de-couple the engine from direct mechanical load requirements combined with regenerative braking). My instinct is that this approach would beat any conventional ICE car by itself, hands down. My initial interest in the Volt was as much for CS mode as for the plug-in, electric-only operation. I still think GM is more likely to be holding their cards very close to the vest due to caution, or some other non-technical reason, rather than trying to deliberately soften news they know will be bad.


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    Nov 23rd, 2009 (1:44 pm)

    coffeetime: I think that the RE mileage will fall somewhere in the mid 30s.I hope I’m wrong.  

    To back up your point, US News reports that GM is saying that the Volt will run about 15% of the time in CS mode, giving it a MPG of 230. Assuming time is linear with miles, this means the Volt would go 34.5 miles on a gallon of gas.

    http://usnews.rankingsandreviews.com/cars-trucks/Chevrolet_Volt/


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    CorvetteGuy

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    Nov 23rd, 2009 (1:45 pm)

    CaptJackSparrow: Back to life after that friggin H1N1 Swine Flu.Graph looks pretty and all but there are no numeric metrics. Means nothing to me other than a graphical illustration of a theoretical principle of operation.There’s still almost a year left for them to tweak. So nothing new.  (Quote)

    I am hoping the value of GM stock shows the same increase as the charging mode on that chart!


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    Nov 23rd, 2009 (1:51 pm)

    CaptJackSparrow: Back to life after that friggin H1N1 Swine Flu.

    Hope you’re feeling better, Cap’n. Did you grow a curly tail? ;-)
    If so, I can recommend an oinkment! :-P

    I thought I might have made you ill with all those pics of your namesake – ! :-(


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    Nov 23rd, 2009 (1:51 pm)

    Sounds like the posters here are pretty much divided about the performance of the Volt. This tells us they speak in generalities and do not divulge actual performance. We know that the Volt will get “up to 40 miles” per charge. But posters vary as to what we will actually get in “normal” driving with house loads on. My 2 cents is the AER will vary from (3.6 miles per Kwh) 28 miles to (4.2 miles per Kwh) 33 miles.
    So the Volt will be a PHEV-30.

    Next we are divided on the cost of the battery pack, with some as high as $16,000, and some as low as $8,000. In my opinion the battery pack will run about $12,000.

    And we are divided as to how the Volt operates in charge sustaining mode. I think the operating points will be close to (1) off; (2) low- less than 1600 RPM putting out about 8 kw, and this operating point will be “imperceptible” to the driver; and (3) mid – about 2800 RPM putting out 24 kwh; and (4) high- close to 4200 RPM putting out 48 kwh. All these operating points fall within the efficiency window of 1200 to 4200 RPM.

    Lastly we are divided on fuel economy in charge sustaining mode, with some clinging to the original “50 MPG” and even some suggesting even more – say 60 MPG, but with the majority accepting the idea the Volt will get about 45 MPG or less in CS mode.

    Many times when Volt performance is addressed we cycle through these well defended opinions as if others who hold differing views are mentally challenged. Guess I will remain stupid in the opinion of others for 12 more months. Maybe less :)


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    Nov 23rd, 2009 (1:58 pm)

    It would be very interesting to know what happens when the car runs out of liquid fuel and one continues driving.
    Traditional cars just choke and the engine stops there, what will the volt’s computer decide?


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    Nov 23rd, 2009 (2:02 pm)

    “We’re optimizing the generator to have different power generating levels.”

    Thank you for calling it “the generator”!

    And I hope that the dashboard displays, not to mention the TV ads, and all references in the owner’s manual also refer to the ICE as “the generator” and not “the engine”.

    This is the simplest way to educate the public about the differences between a VOLT and a Prius. As I said yesterday, it makes perfect sense that “the generator” will (at times) be running at maximum output (read: high rpm’s) even though the vehicle speed may be slowing or even at a stop.

    As long as the dash readout shows the higher rpm’s as “generator output”, there will be no confusion to the driver “hearing” the ICE running fast even though they are not moving.


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    Nov 23rd, 2009 (2:06 pm)

    Paul: It would be very interesting to know what happens when the car runs out of liquid fuel and one continues driving.
    Traditional cars just choke and the engine stops there, what will the volt’s computer decide?  

    A message should appear in bright red letters right in the driver’s main display:

    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!


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    Nov 23rd, 2009 (2:16 pm)

    wwskinn3: I hear that some new “vanadium” batteries may be on the way soon and that they have longer life and a lot more power. Can anyone who knows about them comment.  (Quote)

    11ttydg.gif

    I just googled it, the best article involves using it for something I often threadjack here to promote: grid storage (which is, of course, why I think it is “best”).

    http://www.triplepundit.com/2008/11/vanadium-battery-technology-makes-commercial-progress-as-a-storage-solution-for-renewable-energy/

    There are many other articles which come up in a simple search.


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    Nov 23rd, 2009 (2:20 pm)

    Paul: Traditional cars just choke and the engine stops there, what will the volt’s computer decide?  

    Will the Volt allow you to use the battery reserve to go a bit further?.. I think a GM spokesperson said a while back you would be allowed to dip into those reserves.. but at the risk of damaging the battery.. perhaps GM will give you that option and at the same time void the warranty, an Onstar agent would ask you to authorize it.


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    Nov 23rd, 2009 (2:28 pm)

    Paul: It would be very interesting to know what happens when the car runs out of liquid fuel and one continues driving.Traditional cars just choke and the engine stops there, what will the volt’s computer decide?  (Quote)

    “I’m afraid I can’t do that, Dave. Paul. Whoever.”

    ;-)


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    Nov 23rd, 2009 (2:51 pm)

    More on the Vanadium battery (I think this could be promising):

    “The vanadium redox flow battery was developed by Professor Maria Skylass-Kazacos and her team at the University of New South Wales, Australia. It is a low cost, low environmental impact battery that has a superior deep cycling life and can be mechanically refuelled in minutes.

    The vanadium redox battery stores energy in a liquid electrolyte solution of vanadium pentoxide dissolved in sulphuric acid. The electrolyte can be charged or discharged by pumping it through the battery stack and either supplying electric power to the stack or taking power from the stack. It can also be recharged by having the spent electrolyte pumped out and a fresh charge of electrolyte pumped in.

    The spent electrolyte can then be recharged in another battery with electricity from the mains or from renewable energy sources. This raises the opportunity for the establishment of refuelling stations so that electric vehicles could exchange their electrolyte and then continue on their way with no more delay than if refuelling with petrol or diesel.”

    http://peswiki.com/index.php/Directory:Vanadium_Redox_Batteries

    The system, to me, seems midway between a battery and a fuel cell; one using replinishable liquids rather than tricky gasses. It seems to need two kinds though, so this may not be so straight forward for use in a car (depending on energy per unit of liquid, could it be a solution for over-the-road trucks?).

    Most stories are dated a year or more ago, and most actual work seems aimed at scaling up to electric-utility sizes; so there could be quite a wait before someone brings it out in a four wheeler.

    Anybody know what Vanadium costs, or where in the world it’s found besides in Australia?


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    Nov 23rd, 2009 (2:58 pm)

    Alex and her cruel engineering cohorts are problably sitting in their lab having a good laugh right about now. There is just too much room for speculation in these comments and although I have read all of the comments here I can easily imagine how they are going. The only things I take from this interview are:
    -GM chose to return the Volt to the charge point with as low a charge as possible. This decision to optimize EV mode, dictates that they “sustain” the battery instead of optimize the genset for most efficient output.
    -They have taken the 2-mode design and removed parts of it and added others to optimize for EREV architecture while emphasizing the EV portion of it’s function.
    -There is an opportunity to run the ICE more efficiently by decoupling it mechanically from motive power requirements. EV optimization and NVH may or may not hinder the ability to fully capitalize on this opportunity.
    -Alex speaks in a manner that is open for a lot of interpretation and my head really, really hurts now.


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    Nov 23rd, 2009 (3:15 pm)

    I know there are many posters here with no engineering education. But you should go to Wiki and investigate “Brake Specific Fuel Consumption”, and BSFC maps.

    You will find that the typical ICE operates for a significant amount of the time at very terrible BSFC loads and rpms.

    The great benefit of the Series design from an Engineers perspective, is that the EREV ICE does have to do so very often. In an conventional or Series-parallel hybrid car, e.g. the Prius, the mpg is a composite weighted average of the time it is operating at 100 mpg and the time it is operating at 1 mpg. Using the Series approach you can through away about all the time that it is operating at 1 mpg, as not existing. So you end up with a LOT of time operating at 100 mpg.

    We all know that hyper-milers can use tricks to obtain fantastic mileage figures. Bu they do obtain those mileage figures. Think of the Series setup as letting the Engineers use all those mileage tricks, virtually automatically.

    Alex is not being disingenuous at all. She is speaking precisely. There is exactly ONE spot on that BSFC map that is most efficient. But the region around that optimum spot is really pretty good, and MUCH better than any arbitrary point elsewhere on the BSFC map. Volt engineers, as she says, have NOT chosen to get the optimum CS mileage, by operating the ICE generator only at that optimum point. Instead they will use loads and rpms near the optimum.

    So if the optimum BSFC is say 150 mpg, the region around it may include rpm/load combinations that run from say 100 mpg to that 150 mpg optimum point. Any composite mpg average in such circumstances, will still be damn good.

    I would wager princely sum with anyone who thinks a larger engined Prius running at all points on the BSFC map, can come anywhere near matching the mileage of a 28% smaller engine operating in the sweet spotted region of the BSFC map.


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    Nov 23rd, 2009 (3:39 pm)

    Dave K.: If this is the case. We now understand why GM is holding back on the CS mpg number. Because it will vary greatly with terrain and driver aggressiveness.

    Dave K.: If this is the case. We now understand why GM is holding back on the CS mpg number. Because it will vary greatly with terrain and driver aggressiveness.

    #53

    The EPA mileage ratings we are all waiting for are determined by a highly structured and uniform standard test. I don’t see where individual terrain and driver aggressiveness come into it. As the window stickers say, “Your mileage may vary.”

    I would bet that Alex and her colleagues can simulate those EPA numbers for the “range extender” mode within a very small margin of error right now. Why they are so coy escapes me. I devoutly hope that those who say it’s because they want to blindside the competition with a very high number are right.


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    Nov 23rd, 2009 (3:43 pm)

    Koz: .-They have taken the 2-mode design and removed parts of it and added others to optimize for EREV architecture while emphasizing the EV portion of it’s function.-(Quote)

    I understand her to mean GM is reusing some of the 2-mode software, not hardware.


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    Nov 23rd, 2009 (3:46 pm)

    Noel Park: I would bet that Alex and her colleagues can simulate those EPA numbers for the “range extender” mode within a very small margin of error right now.

    Any time GM wants, they could tell you what the volt will get on the EPA cycles:

    “Manufacturers test their own vehicles—usually pre-production prototypes—and report the results to EPA. EPA reviews the results and confirms about 10-15 percent of them through their own tests at the National Vehicles and Fuel Emissions Laboratory.”

    http://www.fueleconomy.gov/feg/how_tested.shtml


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    Nov 23rd, 2009 (3:55 pm)

    CorvetteGuy: A message should appear in bright red letters right in the driver’s main display:
    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!

    #77

    I don’t need that feature. My wife already does it for me. In addition to being a highly effective speed warning system. As in:

    You are a figgin’ idiot!!! Slow down!!!

    And a collision warning system, and a cornering speed warning system, and many other as well.


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    Nov 23rd, 2009 (3:56 pm)

    Herm:

    Herm Says:
    November 23rd, 2009 at 11:32 am kdawg: GM needs to add a scale to the left side of the chart. I’d like to know the deadband in CS mode.
    Why?.. I would love to know it also but I bet that is one of the things they are working on right now, probably very valuable corporate info.
    It will take GM’s competitors a few months to reverse engineer these settings, and that is after they get their hands on a Volt in early 2011. Its economic warfare.
    We would like it if GM optimized the genset for best CS Mode mileage, but they first have to give the customer a pleasing experience and then they have to satisfy CARB and the EPA.. too many shackles on the engineers.

    Because I’m an engineer and we love data. :)

    Also, i’d like a scale on the time line. Going 70mph on flat terrain in CS mode, i’d like to see how often the generator comes on, and for how long.


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    Nov 23rd, 2009 (4:00 pm)

    Tagamet: BillR
    It’s my understanding that there is no physical connection between the ICE and the wheels. It’s all electric all the time. Am I wrong on that?
    Thanks.
    Be well,
    TagametLet’s Just Get The Volts’ Wheels On The Road!!**********NPNS   

    GM has already stated that they could theoretically replace the gasoline engine/generator with a fuel cell for this Voltec platform – the power source only needs to generate electrical power for the traction motor and battery.

    It would be very difficult to have a mechanical connection between a fuel cell and the wheels :)


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    Nov 23rd, 2009 (4:04 pm)

    MrDuck85: There is a scale on the left. It says 100% at the top, and seems to be linear. Extrapolating with a ruler held to my screen, it appears that the battery hits “full charge” at about 90-95% of capacity, it hits “discharge” at about 30%, the CS band ranges from 30 – 40%, with an “ideal” SOC of about 35%. This is fully in keeping with everything else I’ve read here and elsewhere.  (Quote)

    You may be right, but i’m guessing that chart was not drawn to scale and only used as an illustrative tool.


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    Nov 23rd, 2009 (4:10 pm)

    OT:
    Good article in this month’s issue of Design News on battery technology. Explains differences in chemistry, etc.

    http://www.designnews.com/article/365898-Rechargeable_Batteries_Extend_Their_Reach.php


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    Nov 23rd, 2009 (4:14 pm)

    CorvetteGuy: Paul: It would be very interesting to know what happens when the car runs out of liquid fuel and one continues driving.
    Traditional cars just choke and the engine stops there, what will the volt’s computer decide?

    A message should appear in bright red letters right in the driver’s main display:

    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!
    You are a figgin’ idiot!!! Get out and walk!!!

    AHAHAHAHAHAAA!!!!

    You beat me to it!


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    Nov 23rd, 2009 (4:19 pm)

    stas peterson:
    So if the optimum BSFC is say 150 mpg, the region around it may include rpm/load combinations that run from say 100 mpg to that 150 mpg optimum point. Any composite mpg average in such circumstances, will still be damn good.I would wager princely sum with anyone whothinks a larger engined Prius running at all points on the BSFC map, can come anywhere near matching the mileage of a 28% smaller engine operating in the sweet spotted region of the BSFC map.  

    I sincerely hope so – I am awaiting the results of all these software design decisions next Summer/Fall with optimism.

    I have always thought that 50 mpg in CS mode is quite attainable. The factors pulling down the CS MPG is the weight of the Volt (2950 pounds for Prius, 3520 for Volt) and the larger horsepower (150 hp electric motor in Volt, 137 hp combined power, motor and ICE, in the Prius). Even with the battery buffer allowing a 71 hp engine to feel like a 150 hp electric motor, if people drive aggressively as with a ‘normal’ 150 hp car, the energy requirements might cause a large percentage of the CS mode time spent at maximum ICE rpms, to keep the battery buffer filled.

    The 71 hp engine in the Volt certainly has the potential to be a gas sipper, compared to the 98 hp engine in the Prius, but it remains to be seen what percentage of the time each engine is in maximum rpm bands, how often they are completely off, etc…

    And I hear the Volt will have Sport, Normal and Gas-sipper modes (I wonder if this is for both CD and CS modes – it could be). If people drive in Sport mode, and drive aggressively without caring how much gasoline they use, the CS MPG will certainly go down. But the Gas-sipper mode might be very impressive indeed.


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    Nov 23rd, 2009 (4:33 pm)

    kdawg: Also, i’d like a scale on the time line. Going 70mph on flat terrain in CS mode, i’d like to see how often the generator comes on, and for how long.  

    Maybe Lyle could sneak a CAN bus probe with some memory when he gets his CS Mode ride.. all that data will be there.


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    Nov 23rd, 2009 (4:38 pm)

    Noel Park: The EPA mileage ratings we are all waiting for are determined by a highly structured and uniform standard test. I don’t see where individual terrain and driver aggressiveness come into it. As the window stickers say, “Your mileage may vary.”

    The Volt as it stands now can do the EPA city and hwy cycles fully under electric power (but not one after the other without recharging), so if the just used the standard test the mpg would be infinite since not one drop of gas would be used. They will use new tests for the Volt, the EPA is still working on it.


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    Nov 23rd, 2009 (5:05 pm)

    Shouldn’t there be a “parking” segment of the graph before the “charge mode” segment?!? Ouch! ;)

    Anyway, I still am not quite sure what she is really hinting at. I still get the impression there is some greater interaction between the engine/generator and the traction motor than just generator charges battery, battery powers generator. It’s like, when conditions are just right, they have some other interaction available.

    To my mind, that means using the AC waveforms directly from the generator to power the traction motor. To others, it signals some kind of mechanical linkage.

    I’m hoping for electrical. There could be a very big savings for avoiding the AC->DC and DC-AC steps at low speeds. This old blog from the Tesla Motors folks may help illustrate that:
    http://www.teslamotors.com/blog4/

    Notice their drivetrain’s energy consumption per mile is by far highest at the lowest speeds. From what I recall on induction motors, I would guess that would be typical for any induction motor based drivetrain. So, I would posit that the best place to do some kind of genset/traction motor coupling is at the lowest speeds, where the genset/traction AC voltages could match and NOT at the highest speeds where some kind of mechanical coupling would be more suitable.

    That and I really don’t want a mechanical coupling. :) If it’s truly the most efficient way to do it at this point, then I can probably get over it, but I really want to vote with my checkbook for something with no mechanical coupling to an ICE.


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    Nov 23rd, 2009 (5:10 pm)

    Jackson:
    I just googled it, the best article involves using it for something I often threadjack here to promote:grid storage (which is, of course, why I think it is “best”).http://www.triplepundit.com/2008/11/vanadium-battery-technology-makes-commercial-progress-as-a-storage-solution-for-renewable-energy/There are many other articles which come up in a simple search.  

    Hey Jackson,

    When the vanadium system came out several years ago, I had a discussion with one of my EE friends who is directly knowledgeable regarding it.

    I volunteered to him that it seemed from the illustration above that the energy is stored and released in a very variable rate based on the pumping velocity of the electrolytes. He confirmed that is exactly how it functions (with a note of surprise), and, added a few other comments. One thing he mentioned was that the electrolytes are extremely corrosive.

    If it leaked, that situation may suggest a very unsafe condition for a moving source of energy as is required for an EV.

    Remote applications out in wind-energy areas of the country might prove an excellent application of it , however.


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    Nov 23rd, 2009 (5:19 pm)

    Hey, did we ever learn EXACTLY how that 230mpg number came about? Because if anybody has spilled the beans on the (and it has to be the exact) measurement technique, we can probably back calculate the CS mileage pretty well. I remember we were guessing at it at the time it came out. Perhaps the EPA or somebody has released some more information since then?

    Anyway, we should keep our eyes open. At some point I would guess that the EPA metrics for EREV will be available (hopefully before they go on sale) and possibly before GM says what the CS mileage is. :)


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    Nov 23rd, 2009 (5:24 pm)

    Rooster: I understand her to mean GM is reusing some of the 2-mode software, not hardware.  (Quote)

    Re-reading that answer leads me to agree she is only speaking about software here.


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    Nov 23rd, 2009 (5:27 pm)

    Stas P. said
    “I would wager princely sum with anyone who thinks a larger engined Prius running at all points on the BSFC map, can come anywhere near matching the mileage of a 28% smaller engine operating in the sweet spotted region of the BSFC map.”

    The Prius does not operate at “all points” on the BSFC map. The Toyota engineers have it programmed to operate along its best SFC line just like the Volt. That is one of the ways they get such good mileage.


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    Nov 23rd, 2009 (5:33 pm)

    stas peterson: I would wager princely sum with anyone who thinks a larger engined Prius running at all points on the BSFC map, can come anywhere near matching the mileage of a 28% smaller engine operating in the sweet spotted region of the BSFC map.

    stas peterson: I would wager princely sum with anyone who thinks a larger engined Prius running at all points on the BSFC map, can come anywhere near matching the mileage of a 28% smaller engine operating in the sweet spotted region of the BSFC map.

    #83

    To borrow once again from our good friend Tagamet:

    “From your lips to God’s ears.” +!


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    Nov 23rd, 2009 (5:35 pm)

    Edit to #101:

    I dunno why it’s putting the quote up twice. I thought that I had made some kind of mistake the first time, but not this time.

    Oh well, the comments I quote are worth repeating twice anyway, LOL. Keep up the good work guys!


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    Nov 23rd, 2009 (5:36 pm)

    Geronimo: The factors pulling down the CS MPG is the weight of the Volt (2950 pounds for Prius, 3520 for Volt)…

    Other than inertia (which is taken care of nicely by the torque of the electric drive) the weight has very little to do with gas mileage. The aero is way more important even at city speeds. Thus the Volt will be better than the Prius just on aero alone.


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    Nov 23rd, 2009 (5:37 pm)

    DaveP: Shouldn’t there be a “parking” segment of the graph before the “charge mode” segment?!?Ouch!
    Anyway, I still am not quite sure what she is really hinting at.I still get the impression there is some greater interaction between the engine/generator and the traction motor than just generator charges battery, battery powers generator.It’s like, when conditions are just right, they have some other interaction available.To my mind, that means using the AC waveforms directly from the generator to power the traction motor.To others, it signals some kind of mechanical linkage.I’m hoping for electrical.There could be a very big savings for avoiding the AC->DC and DC-AC steps at low speeds.This old blog from the Tesla Motors folks may help illustrate that:
    http://www.teslamotors.com/blog4/Notice their drivetrain’s energy consumption per mile is by far highest at the lowest speeds.From what I recall on induction motors, I would guess that would be typical for any induction motor based drivetrain.So, I would posit that the best place to do some kind of genset/traction motor coupling is at the lowest speeds, where the genset/traction AC voltages could match and NOT at the highest speeds where some kind of mechanical coupling would be more suitable.That and I really don’t want a mechanical coupling. If it’s truly the most efficient way to do it at this point, then I can probably get over it, but I really want to vote with my checkbook for something with no mechanical coupling to an ICE.  

    Hey DaveP
    Just some speculation on my part. But, what if, at battery end-of-life, where you have an owner that under no circumstances can be in a position to get another battery, and, must just drive the vehicle. Maybe there is a way to use the very very last amount of energy storage capability of the battery (say, at year 15?), in order to make the Volt behave like a standard hybrid after 15 years?.

    This is not saying that the powertrain is designed to be the same as a Hybrid whatsoever in the preceding 15 years. It is saying that the cost of replacement packs might take as long as 12 to 14 years for that same “second” or “third” owner to re-invest.

    It wouldn’t be fair at all to say that the Volt powertrain is designed as a direct drive if my speculation had any merit. The reason why I am speculating some “far into the future, a GM-way of taking care of the Volt owner even at 15 years out”, is because GM is the company that thinks in terms of its customers needs that far out and well beyond. (Not a commercial image of a Prius made of sticks and leaves that literally “blows away in the wind” to be recycled presumably. All too soon when the owner does not have the $4000 for a traction battery at year six, which irritates the heck out of me for an obsolete technology that ought to cost about $800 bucks for that dang battery!!!)

    Ask any other OEM about their customer who bought one of their vehicles fifteen years ago, and, they might react like “No money to be made there”.

    GM’s business model takes care of the oldest GM customer’s vehicle just like the newest GM customer’s latest model.
    A true and substantial reason to trust that GM is doing the best possible job in bringing us the Volt.


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    Nov 23rd, 2009 (5:40 pm)

    Noel Park: You are a figgin’ idiot!!! Slow down!!!

    No contractions or cursing? That’s a keeper.


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    Nov 23rd, 2009 (5:41 pm)

    Herm: The Volt as it stands now can do the EPA city and hwy cycles fully under electric power (but not one after the other without recharging), so if the just used the standard test the mpg would be infinite since not one drop of gas would be used.

    #95

    I’m just saying, if they want us to know what the “RE” mileage is, they can just run the cycles with the car in RE mode the whole cycle. Or just start them with the battery down to the minimum level, and see what happens. I want to know what the EPA mileage will be, city, highway, and combined, after the AER ends. How complicated can that be?


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    Nov 23rd, 2009 (6:04 pm)

    stas peterson: Using the Series approach you can through away about all the time that it is operating at 1 mpg, as not existing. So you end up with a LOT of time operating at 100 mpg.

    Thanks, This was the reason i was thinking Volt will give a 70+ mpg on average and 50-150 mpg according to the load and other factors on real time driving conditions.Still i dont have reasons to think volt will only give 50 mpg on CS mode ( should be around and above 70) But problem is none ever done the full workout of range extender EV maths and did a demo.


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    Nov 23rd, 2009 (6:09 pm)

    DaveP: Hey, did we ever learn EXACTLY how that 230mpg number came about? Because if anybody has spilled the beans on the (and it has to be the exact) measurement technique, we can probably back calculate the CS mileage pretty well. I remember we were guessing at it at the time it came out. Perhaps the EPA or somebody has released some more information since then?Anyway, we should keep our eyes open. At some point I would guess that the EPA metrics for EREV will be available (hopefully before they go on sale) and possibly before GM says what the CS mileage is.   (Quote)

    I understand the ran the city cycle repeatedly in EV mode until the ICE started, and then measured the total distance traveled. Then they repeated 1 more city cycle in charge sustaining mode. Lastly, they took the total miles traveled (both EV and CS) and divided by the gas used.

    For example, the city loop is approximately 11 miles, and the Volt can travel 40 miles in EV mode. If it then gets 50 miles per gallon in CS mode on the city cyle, the math is the following:

    11 miles / 50 mpg = .220 gallons consume

    Total distance = 40 + 11 = 51 miles

    MPGe = 51/.220 = 231


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    Nov 23rd, 2009 (6:12 pm)

    Loboc:
    Other than inertia (which is taken care of nicely by the torque of the electric drive)the weight has very little to do with gas mileage. The aero is way more important even at city speeds. Thus the Volt will be better than the Prius just on aero alone.  

    Not true.

    The kinetic energy of a moving car is 1/2m*s^2, where m is the mass, and s is the speed.
    When in CS mode, all the energy ultimately comes from the gasoline (even regenerative braking just recaptures a fraction of energy that came from gasoline before). Any energy put into the battery buffer while driving is also from gasoline.
    So, the energy needed to go from 0 to speed s is directly proportional to mass (weight, on Earth). Double the weight of a car, you need twice the energy (gasoline burned) to get to the same speed (for that car). The Volt is 15.7 % heavier than the 2010 Prius, so this will affect MPG, but there are other factors as well.
    (I found the 2010 Prius is 3042 pounds; 2950 was for an older Prius).

    Rolling resistance of the tires is proportional to the weight – luckily Volt will use low resistance tires from Goodyear (Assurance Fuel Max tires) but the Prius also has low rolling resistance tires.

    As for aerodynamics, yes they are important, but the Cd of the Volt and Prius are very similar – I think the Volt attained a Cd of 0.24, but the Prius is 0.25, not much bigger:
    http://www.toyota.com/prius-hybrid/specs.html
    Perhaps the Volt has less cross sectional Area, which is also proportional to the Air Drag, but I don’t think it would be much smaller than the Prius

    The biggest unknowns right now are how GM uses the fuel-sipping gas engine in combination with their very large battery buffer – in “Fuel Saving” mode, this might give very good MPG, indeed.

    But the extra weight is a negative factor. The more steel they replace with aluminum in the future, the better.


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    Nov 23rd, 2009 (6:38 pm)

    Noel Park: I’m just saying, if they want us to know what the “RE” mileage is, they can just run the cycles with the car in RE mode the whole cycle. Or just start them with the battery down to the minimum level, and see what happens. I want to know what the EPA mileage will be, city, highway, and combined, after the AER ends. How complicated can that be?  

    I see what you are saying, first number on the sticker would be 40 miles of gas free driving, and the second set of numbers would just be standard city and hwy cycles in the CS Mode.. probably not a bad way to do it, fairly simple.


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    Nov 23rd, 2009 (6:40 pm)

    Herm:
    Maybe Lyle could sneak a CAN bus probe with some memory when he gets his CS Mode ride.. all that data will be there.  

    Hey Herm,

    LOL.
    Not gonna happen. Nothing will get into that little Volt IVER OBD2 connector even if there was one there.
    Even if there was access allowed, no one but GM would know what is going on with those datasets in that EV subprocessor.
    (Although I did have the opportunity to get all of Prius’s about 2 years ago (LOL)). (NOT PARTICULARLY IMPRESSIVE). (…..overpriced “two-block battery”, [grumble...,lol].)


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    Nov 23rd, 2009 (6:49 pm)

    Dan Petit: Just some speculation on my part. But, what if, at battery end-of-life, where you have an owner that under no circumstances can be in a position to get another battery, and, must just drive the vehicle. Maybe there is a way to use the very very last amount of energy storage capability of the battery (say, at year 15?), in order to make the Volt behave like a standard hybrid after 15 years?.

    GM has stated before that as time goes on the Volt will automatically adjust the SOC parameters, but that you will still have the 40 miles of electric range.. so lets say at year 10 the Volt discharges the pack down to 10% to still get that 40 miles of range.. then on year 11 it starts to cut down on the electric range and you only get 35 miles, perhaps all the electric range will be gone by the 15-20th year so that the car will operate in the CS Mode all the time with the small remaining capacity.. to buffer the motor, perhaps 0.5kwh left.. once that is gone you will have a very underpowered Volt. The Volt battery may have a very gradual decline as it ages.


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    Nov 23rd, 2009 (6:50 pm)

    Dan Petit: When the vanadium system came out several years ago, I had a discussion with one of my EE friends who is directly knowledgeable regarding it.

    THANK YOU for first hand information!

    There’s always a catch, isn’t there? Heh.


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    Nov 23rd, 2009 (7:00 pm)

    Dan Petit: Herm:
    Maybe Lyle could sneak a CAN bus probe with some memory when he gets his CS Mode ride.. all that data will be there.
    Hey Herm,
    LOL.
    Not gonna happen. Nothing will get into that little Volt IVER OBD2 connector even if there was one there.
    Even if there was access allowed, no one but GM would know what is going on with those datasets in that EV subprocessor.
    (Although I did have the opportunity to get all of Prius’s about 2 years ago (LOL)). (NOT PARTICULARLY IMPRESSIVE). (…..overpriced “two-block battery”, [grumble...,lol].)

    We just need to hack into their OnStar transmission. A couple of the posters here are in the area of their testing facility…


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    Nov 23rd, 2009 (7:02 pm)

    Herm:
    GM has stated before that as time goes on the Volt will automatically adjust the SOC parameters, but that you will still have the 40 miles of electric range.. so lets say at year 10 the Volt discharges the pack down to 10% to still get that 40 miles of range.. then on year 11 it starts to cut down on the electric range and you only get 35 miles, perhaps all the electric range will be gone by the 15-20th year so that the car will operate in the CS Mode all the time with the small remaining capacity.. to buffer the motor, perhaps 0.5kwh left.. once that is gone you will have a very underpowered Volt.The Volt battery may have a very gradual decline as it ages.  

    Herm,
    We could not be in more precise and exact agreement. I really think GM is the only OEM to trust in all of this EREV development.

    Doesn’t this really portend that all the other OEM’s must be really “up the creek” or even “down the creek headed towards the falls” regarding electrification?

    How do any of these other OEM’s maintain any belief systems that have them at any ease whatsoever to accept that a large proportion of their customers will consider them anything but outmoded, technically-entrenched to carbon, and beholden to (non)technical- curmudgeons-in-charge?

    I really think the rest of the OEM’s are shortly going to be in really deep trouble with their [ex]customers, and,
    it will all
    hit them all
    like a brick wall
    in about 11 more months.


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    Nov 23rd, 2009 (7:15 pm)

    Jackson:
    THANK YOU for first hand information!There’s always a catch, isn’t there?Heh.  

    Hey Jackson,
    Yes, but it’s the relentless drive to “fix the catch” that gets us moving forward in any new invention. Vanadium might have an honored place in our electrification process to store overnight wind energy reserves. We’ll just have to see and be patient for those inventors as well.


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    Nov 23rd, 2009 (7:25 pm)

    Koz:
    We just need to hack into their OnStar transmission. A couple of the posters here are in the area of their testing facility…  

    LOL. Nope; Not gonna happen either. LOL

    Only Uncle Sugar has the decryption technology to see how to figure out Volt if any datum went wireless. (Ok, no ownership jokes please relating to that last sentence. (I think GM stock is going to skyrocket. And, I am going to buy a little of it myself just to have a piece of electric motoring manufacturing leadership history.))


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    Nov 23rd, 2009 (7:41 pm)

    Noel Park: can simulate those EPA numbers

    Noel Park: a very high number

    To quote Barack Obama, “There is nothing false about hope”.

    The management at NGMCO is being open with news concerning the latest systems and advances regarding the Volt. The two question marks currently in the public eye are tank size and CS mpg. The size of the tank will be a trade off between advertised total range and added overall weight (which lowers initial battery range).

    The CS range number is tied to body aero, overall vehicle weight, and generator system fine tuning. NGMCO has stated this (in one way or another) dozens of times. I believe them when they say, “Fine tuning to be done”.

    Let’s hope the final CS numbers are strong. And let’s also hope we see the Volt sticker at $39k.

    $39k plus 10% (taxes ~ license ~ fees) = $42,900

    $42,900 – $7500 (tax credit) = $35,400

    Most new 4dr, leather, GPS sedans carry $28,000+ out the door pricing. The Volt is an attractive alternative to burning countless drums full of gasoline. The Volt will cost at least $1000 less per year to fuel than a gasoline sedan. These savings will multiply when opportunity charging and rising gasoline costs are taken into account.

    =D~


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    Nov 23rd, 2009 (7:42 pm)

    Dan Petit:
    LOL. Nope; Not gonna happen either. LOL Only Uncle Sugar has the decryption technology to see how to figure out Volt if any datum went wireless.(Ok,no ownership jokes please relating to that last sentence.(I think GM stock is going to skyrocket. And, I am going to buy a little of it myself just to have a piece of electric motoring manufacturing leadership history.))  

    Footnote,
    Although stock certificates aren’t actually issued anymore from what I understand, I would want a certificate issued with the GM seal on it to frame and hang up over my desk as a testimonial that I support GM’s electrification process, and, I really want a certificate to frame.


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    Nov 23rd, 2009 (7:43 pm)

    Ok, one more “mechanical conspiracy” thought. (and probably somebody’s already mentioned this on one of Cattelan’s two threads but I didn’t see it right off):

    If you look at the 11/9/09 post, Cattelan says this:

    ” in EV operation I have two motors on board and I typically use the traction motor only to drive the vehicle. However, I do have some mechanisms to couple those motors and in some points of operation these two motors can be coupled and have a more efficient state.”

    She does say “EV OPERATION”, which may very well mean in “CD MODE”. If so, then she’s just saying that the generator is (in charge depleting mode) de-clutched from the ICE and is acting as an electric motor to drive the wheels along with the traction motor. That the generator acts as both a generator AND as a traction motor (but not as a traction motor when it’s engaged to the ICE (CS MODE). They are doing this to get better efficiency out of the electrical motor combination (thus using fewer kwh/mi while draining the battery in CD mode). I think this would explain everything she’s saying while still keeping the Volt’s series hybrid label intact.


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    Nov 23rd, 2009 (7:51 pm)

    By the time Volt comes out, no other “label” will suffice.

    “Volt” will be it’s only label that anyone will really care about. All the other words will just pass away and be left in the dust where they belong.


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    Nov 23rd, 2009 (7:54 pm)

    Dan Petit: By the time Volt comes out,no other “label” will suffice.“Volt” will be it’s only label that anyone will really care about. All the other words will just pass away.  

    I hope you’re keeping both hands on the keyboard.


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    Nov 23rd, 2009 (7:58 pm)

    carcus1: If so, then she’s just saying that the generator is (in charge depleting mode) de-clutched from the ICE and is acting as an electric motor to drive the wheels along with the traction motor. That the generator acts as both a generator AND as a traction motor (but not as a traction motor when it’s engaged to the ICE (CS MODE).

    I think you’re right.
    But does 2 electric motors run more efficient than one? Or better does 2 electric motors run more efficient that a big azz one?


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    Nov 23rd, 2009 (8:02 pm)

    CaptJackSparrow:
    I think you’re right.
    But does 2 electric motors run more efficient than one? Or better does 2 electric motors run more efficient that a big azz one?  

    I think different motors run more efficiently at different speeds/loads. DaveP or Herm or somebody is probably up on that. I know I’ve read that the harder you run them, the more efficiency drops off, so maybe in tandem it’s just less heat and better efficiency.

    /p.s. sorry about your pig flu. Seems like everybody’s getting it. I had to hold my breath in wal-mart today when I went in for a set of wife beater T’s and some scotch buy beer.


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    Nov 23rd, 2009 (8:22 pm)

    George S. Bower: Not putting in a complex tranny is about COST. Even though it would make the CSM MPG better, the volt is already so expensiveit’s just not an economically sound decision.  

    It’s not just cost, everything you don’t want in an EV is encumbant in a complex transmission. It affects weight efficiency


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    Nov 23rd, 2009 (8:45 pm)

    carcus1: Ok, one more “mechanical conspiracy” thought. (and probably somebody’s already mentioned this on one of Cattelan’s two threads but I didn’t see it right off):If you look at the 11/9/09 post, Cattelan says this:” in EV operation I have two motors on board and I typically use the traction motor only to drive the vehicle. However, I do have some mechanisms to couple those motors and in some points of operation these two motors can be coupled and have a more efficient state.”She does say EV OPERATION, which may very well mean in CD mode.If so, then she’s just saying that the generator is (in charge depleting mode) de-clutched from the ICE and is acting as an electric motor to drive the wheels along with the traction motor.That the generator acts as both a generator AND as a traction motor (but not as a traction motor when it’s engaged to the ICE).They are doing this just to get better efficiency out of the electrical motor combination (thus using fewer kwh/mi while draining the battery in CD mode).I think this would explain everything she’s saying while still keeping the Volt’s series hybrid label intact.  

    Too complicated. I doubt that decouple = declutch. Less complicated would be that in CS mode, the generator could use ac ‘coupling’ to avoid ac>=dc>=ac conversions.


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    Nov 23rd, 2009 (8:45 pm)

    carcus1: /p.s. sorry about your pig flu. Seems like everybody’s getting it. I had to hold my breath in wal-mart today when I went in for a set of wife beater T’s

    I thouht wife beater T’s come with H1N1


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    Nov 23rd, 2009 (8:59 pm)

    loboc: Too complicated.

    You think what I said was complicated? Try this:

    “The 2MT70 transaxle itself is extremely compact at a mere 15 inches in length and has the potential to bring two-mode architecture to a wider range of vehicles. It is scalable across front-wheel-drive vehicles with engines that range from a 2.0litre four-cylinder turbo-diesel to a 3.6litre direct injection, spark ignition V6 petrol engine.
    As the two-mode design uses motor B to produce all reverse torque, scaling the transaxle for a larger or faster vehicle normally involves extending the length of motor B and redesigning the end casting of the transaxle so that it accommodates the increase in motor length.
    It uses two 55kW active-cooled AC motor generators, each of which is connected to a planetary gearset and is capable of providing either a continuously variable speed or motive power. It uses a combination of engine speeds, motor speeds and a system of clutches to manipulate the planetary gearsets and provide two variable ranges as well as a compound split that allows the ranges to influence each other.
    The project’s engineers have also developed a damper bypass clutch that couples the engine and transmission during stop/start transitions – this smoothes the operation.”
    http://www.thegreencarwebsite.co.uk/blog/index.php/2009/05/11/general-motors-previews-hybrid-transaxle/

    or this:

    http://en.wikipedia.org/wiki/Global_Hybrid_Cooperation

    /makes the HSD in the Prius look like child’s play (and that’s not necessarily a good thing)


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    Nov 23rd, 2009 (9:06 pm)

    koz:
    I thouht wife beater T’s come with H1N1  

    Nah, but you can use the plastic packaging as a make-shift cooler for the beer . . . . if you’re careful.


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    Nov 23rd, 2009 (9:55 pm)

    Koz: No contractions or cursing? That’s a keeper.  (Quote)

    Hey. I’m married too. When the wife says slow down, it’s best to do so, or it will just get louder and louder and louder!!!


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    Nov 23rd, 2009 (10:11 pm)

    Geronimo: I have always thought that 50 mpg in CS mode is quite attainable. The factors pulling down the CS MPG is the weight of the Volt (2950 pounds for Prius, 3520 for Volt) and the larger horsepower…

    You forgot a factor, one that affects efficiency quite a bit: EMISSIONS

    How dirty will the engine be allowed, for that matter accepted?

    Look at the penalties involved with delivering a SULEV rating.


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    Nov 23rd, 2009 (10:21 pm)

    We need some sort of flow chart, ICE permanently connected to generator? yes/no? Generator connected to to wire controller thingy with wires directly to traction motor yes/no? Wire controller thingy uses a small portion of battery as a power buffer if traction motor needs more energy than the ICE/Generator can produce at any given time yes/no? Traction motor connected directly to wheels with a gear reduction yes/no?

    It is my assumption that the resistance of the generator can be used to keep the ICE in its sweet spot range. yes/no? If the generator produces more power than necessary the ICE will shut down for a bit of time yes/no? Now through in a bunch off arrows and more what ifs and you got yourself a flow chart.

    Now an ICE that runs at it’s sweet spot will be more efficient than an ICE running at a speed dictated by a gear set and vehicular speed. The question is what are the efficiency losses of the wire to motor thingy and battery buffer…

    /from reading other thoughts here, my wild a$$ guess, 44mpg.
    Group 44


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    JeremyK

     

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    Nov 23rd, 2009 (10:41 pm)

    Stas hit the nail on the head…couldn’t have said it better myself so I won’t try.

    My understanding is that the base engine used in the Cruze, will be a turbo version of the 1.4L…and if they can get 40 mpg hwy with that, then surely they can do better with a NA version in the Volt running near optimum BSFC.

    +1 on BillR’s assessment of the power flow. This is exactly the type of configuration a company like GM would use. It’s a new way of using old/proven technology and a familiar FWD powertrain layout. When I hear Alex use the word “decoupled”, the engineer in me hears “it can also be coupled”…mechanically.


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    LRGVProVolt

     

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    Nov 23rd, 2009 (10:44 pm)

    #80

    Jackson:
    “I’m afraid I can’t do that, Dave.Paul.Whoever.”   

    LoL :)

    Happy trails to you ’til we meet again.


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    LRGVProVolt

     

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    Nov 23rd, 2009 (10:47 pm)

    #69

    BillR: eliminate some of the losses associated with converting AC power from the genset to DC power and then back to AC power at the proper frequency and voltage.

    The only time that the power from the ICE motor/generator would be needed to convert to DC is when it is charging the battery pack. Otherwise it is just blended with the power from the battery pack which has been converted from DC to AC. There is no loss as you describe it for this reason.

    Happy trails to you ’til we meet again.


  136. 136
    LRGVProVolt

     

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    Nov 23rd, 2009 (11:20 pm)

    Earlier I stated that the Volt battery pack is only charged to 80% SOC. Based upon what others have stated, I decided to check out the facts on this issue. The correct figure is 85%!

    Check out: http://en.wikipedia.org/wiki/Chevrolet_Volt#Battery

    There is a lot of information at this link that may answer some of your questions.

    Happy trails to you ’til we meet again.


  137. 137
    Herm

     

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    Nov 23rd, 2009 (11:47 pm)

    koz:
    I thouht wife beater T’s come with H1N1  

    God have mercy on me, I had to google this..

    http://www.wifebeatershirt.com/


  138. 138
    Herm

     

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    Nov 23rd, 2009 (11:51 pm)

    LRGVProVolt: Earlier I stated that the Volt battery pack is only charged to 80% SOC. Based upon what others have stated, I decided to check out the facts on this issue. The correct figure is 85%!
    Check out: http://en.wikipedia.org/wiki/Chevrolet_Volt#Battery

    This may be wrong, I have always heard a total usable capacity of 8kwh, for an SOC of only 50% total.. the battery charge level ranges from 80% to 30%.. obviously this is a very conservative regimen.


  139. 139
    Rooster

     

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    Nov 23rd, 2009 (11:52 pm)

    loboc: Too complicated. I doubt that decouple = declutch. Less complicated would be that in CS mode, the generator could use ac ‘coupling’ to avoid ac>=dc>=ac conversions.  (Quote)

    Agree,

    BTW, does the following sound familar to anyone?

    A phase converter is a device that converts electric power provided as single phase to multiple phase or vice-versa. Several methods exist to run three-phase motors from a single-phase supply, one of which is called a Rotary Phase Converter (RPC) which is constructed from a three-phase electric motor or generator “idler”. This is a two motor solution. One motor is not connected to a load and produces the three phase power, the second motor driving the load runs on the power produced. The main principles of RPC operation are as follows:

    Three phase induction motors have three terminals called “legs”, usually numbered (arbitrarily) L1, L2, and L3.

    A three phase induction motor can be run at two-thirds of its rated horsepower on single phase power applied to any pair of legs, once spun up by some means.

    A three phase induction motor that is spinning under single phase power applied to legs L1 and L2, generates an electric potential (and can deliver power through) leg L3, although without some form of current injection, special windings in the idler, or other means the voltage will sag when a load is applied.

    Power factor correction is a very important consideration when building or choosing an RPC. Power factor correction is desirable because an RPC that has power factor correction will consume less amperage from the single-phase service supplying power to the phase converter and its loads.

    http://en.wikipedia.org/wiki/Phase_converter


  140. 140
    Herm

     

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    Nov 24th, 2009 (12:15 am)

    Rooster: loboc: Too complicated. I doubt that decouple = declutch. Less complicated would be that in CS mode, the generator could use ac ‘coupling’ to avoid ac>=dc>=ac conversions.  (Quote)
    Agree,
    BTW, does the following sound familar to anyone?

    I think it also works this way, but its not a direct connection from the generator to the motor.. if you did this then rpms of both motors would be locked together (electrically) and thus ICE rpm would have to follow the speed of the car.. there is an AC-AC conversion in each leg of the motor.


  141. 141
    Matthew B

     

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    Nov 24th, 2009 (2:21 am)

    BillR:
    One of her quotes,
    “We do have the ability to utilize both motors in propulsion mode.”I don’t profess to have the answer, but have only offered a possibility that uses both motors in propulsion mode, uses something similar to the 2-mode transmission, and provides a variable speed drive for thetraction motor.  

    I really wonder if this is a “trick” up GM’s sleeve. If they have the ability to switch to direct connection at freeway speeds I could easily see them beat the Prius’s highway mileage numbers.

    The Prius is unable to shut down the engine above 45 MPH due to the power split design. The Volt won’t have this limitation and if that’s coupled with the ability to switch to a parallel hybrid at high speed than it may be setting a MPG record outright in CS mode.


  142. 142
    Matthew B

     

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    Nov 24th, 2009 (2:28 am)

    George S. Bower: Not putting in a complex tranny is about COST. Even though it would make the CSM MPG better, the volt is already so expensiveit’s just not an economically sound decision.  

    With motors on both shafts to force synchronization, it could be as simple as a jaw clutch and a small motor actuator. The engine MG could be commanded to match the speed of the drive MG, and then the two shafts could be coupled with a jaw clutch. This mode would be just like high gear in a conventional manual transmission with the benefit of the motors to act like a parallel mode hybrid.

    Given that a 5 speed manual transmission has 5 such clutches (plus synchros), the cost isn’t a whole lot.


  143. 143
    Herm

     

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    Nov 24th, 2009 (2:33 am)

    Matthew B: The Prius is unable to shut down the engine above 45 MPH due to the power split design. The Volt won’t have this limitation and if that’s coupled with the ability to switch to a parallel hybrid at high speed than it may be setting a MPG record outright in CS mode.  

    That has been changed in the 2010 Prius, they can now go up to 62mph before turning on the engine and they also have an EV Mode switch installed, it forces an EV only operation when possible.. Toyota is getting ready to offer a plug-in option on the Prius.


  144. 144
    Matthew B

     

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    Nov 24th, 2009 (2:39 am)

    LRGVProVolt:
    The only time that the power from the ICE motor/generator would be needed to convert to DC is when it is charging the battery pack. Otherwise it is just blended with the power from the battery pack which has been converted from DC to AC. There is no loss as you describe it for this reason.Happy trails to you ’til we meet again.  

    Both motor / generators in the Volt are AC. If they are operating at the same exact speed then the two could be paralleled together. But I doubt that’d ever be done because then the engine must operate at a fixed speed in relation to road speed.

    Far more likely would be for the power to always be converted into DC as an intermediate step to allow for frequency conversion.


  145. 145
    Mohsen

     

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    Nov 24th, 2009 (2:59 am)

    LRGVPvolt – You cant just connect an AC generator to an AC motor. If you do, then they will have to be in absolute sync! I.e. the generator (and the ICE) must run at exactly the wheel speed.

    Since this is impossible without a mechanical linkage, they will go out of phase and all hell will break loose. Like frying your motor or generator.

    In any case, the interview makes it obvious that in mode-2 the ICE is connected to the wheels, and that its a parallel machine. I suppose in mode-1 its a serial machine.


  146. 146
    Dave K.

     

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    Nov 24th, 2009 (6:44 am)

    volt%20with%20model.jpg

    Performed a net search for Volt photos featuring the Euro hood design change. Very few larger shots available. Here is a good pre-Euro glam shot of the Volt with a model.

    =D~


  147. 147
    Dr. Ibringdoh

     

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    Nov 24th, 2009 (10:06 am)

    So to boil this down in a nutshell, Alex believes that the efficiency gained by not having the output directly tied to the torque requests from the driver will more than offset the multiple 2nd Law efficiency losses of having intermediate steps between engine output and torque generation.

    The true answer to this question is somewhat driver dependent, but Alex makes a fair point: significant losses of fuel efficiency are incurred when applying torque and accelerating the engine. What makes hybrids so efficient in cities is that electrical energy is used to supply initial torque, thereby replacing part of the fuel consumption required when accelerating a vehicle from a stop.

    The best of possible worlds, of course, is to have engine torque applied directly to the wheel when maintaining speeds and not at all when torque is demanded by the driver — but the 2nd Law implications of such a system may be even greater than those incurred by not having the engine tied to the torque at all.

    Respectfully,

    Dr. Ibringdoh


  148. 148
    Engineer

     

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    Nov 24th, 2009 (10:49 am)

    OH these are my favorite types of posts, actually talking with the engineering side of things and getting into the nitty gritty. I much prefer this over the “hype” and opinionated ones.


  149. 149
    DaveP

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    Nov 24th, 2009 (5:54 pm)

    Well, I have to admit that the mechanical conspiracy theorists (you know who you are ;) make some good points. Especially important is that the entire mechanism is undoubtedly more like the 2 mode hybrid than the equinox fuel cell drive.

    So, what does that mean? The two mode has 3 planetary gearsets and 2 clutches, plus 2 clutch brakes. Now, to keep costs down compared to the actual two mode, they’re going to throw out the parts they don’t need. Let’s take a look at what that might mean.

    What’s interesting here is if we interpret Alex’s comments as Carcus1 has, that the motors can be clutch coupled when operating in CD mode, not necessarily CS mode. Or, rather, you could use both motors as traction motors simultaneously.

    The two modes I see that state in are (and I’m looking at the wikipedia entry for the two mode hybrid, http://en.wikipedia.org/wiki/Global_Hybrid_Cooperation ) second power split mode operation, first fixed ratio or 3rd fixed ratio.

    Then, to operate the drive only on the traction motor, it would be necessary to switch to either second power split mode 3rd fixed gear ratio or first power split mode.

    Now, it looks like you could accomplish the switch between 2nd power split mode, first fixed ratio and 1st power switch mode by simply switching the state of clutch 4.
    (All the other clutches are in the same state, so they can be removed.)
    Similarly, you could switch between 2nd power split mode first fixed ratio or 3rd fixed rato and 2nd power split mode, 2nd ratio by changing the state of two clutches.

    However, the intended situation for 2nd power split mode is that the engine is running all the time, providing power to the system for traction. I’m not sure what happens if you try to stop the engine. The motors will probably try to turn it unless it is braked with a clutch. You certainly can’t just decouple it with a clutch or that node of the planetary gearset will spin free effectively freezing the motors.

    Using the two mode transmission, I don’t see it as simple at all to achieve a relatively simple mechanical coupling. You’d need most all of the two mode parts. If you toss out the idea of a mechanical coupling, you can toss out (I think) one planetary gearset and 4 clutches, leaving two planetary gearsets and two motors. Depending on the design you might be able to toss out the input side planetary gearset (which would just adjust the ratio between the engine and generator motor).

    Of course, the’ve had plenty of time to think about it and may have come up with something else clever (clutching together the 3rd node of the planetary gearsets?!?) I don’t know. Right now, I just don’t see any way to achieve mechanical coupling much short of the full two mode setup. It’s an interesting line of thought, though. We should continue to look for clues. :)


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    Matthew B

     

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    Nov 25th, 2009 (12:11 am)

    Mohsen: LRGVPvolt – You cant just connect an AC generator to an AC motor.If you do, then they will have to be in absolute sync!I.e. the generator (and the ICE) must run at exactly the wheel speed.Since this is impossible without a mechanical linkage, they will go out of phase and all hell will break loose.Like frying your motor or generator.In any case, the interview makes it obvious that in mode-2 the ICE is connected to the wheels, and that its a parallel machine.I suppose in mode-1 its a serial machine.  

    It is possible to sync up the two motors electronically and then parallel them for direct transfer. Once they were paralleled they would stay in phase just like generators on the power system do. In the Volt the problem would remain that it forces the ICE speed to match wheel speed. It could be done to save maybe 5% or so losses at freeway speed if the speed of the ICE was acceptable for the given load.

    To sync them up first a frequency comparator provides the input to a feedback loop that controls the torque on the drive and then once the frequency matches it’s switched over to a phase comparator. When the phase comparator is steady and within bonds the signal is given to parallel in.

    I’ve designed converters that do just that for both large synchronous motors and large induction generators. So long as there isn’t a wildly varying mechanical load it’s not too difficult. Windmills in gusty conditions can get a bit tricky to do reliably.


  151. 151
    Mohsen

     

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    Nov 25th, 2009 (1:49 am)

    Matthew B: So long as there isn’t a wildly varying mechanical load it’s not too difficult. Windmills in gusty conditions can get a bit tricky to do reliably.  (Quote)

    You have a wheel speed that can vary considerably – from 100 mph to absolute zero when the driver slams on the breaks. There is no way you can throttle the ICE to match these conditions. There is so much response that throttling can give you and not the kind of response that you would need in an AC-to-AC EV connection.

    There is no question that in such a case, they will go out of sync. Question really is how much damage would that cause and how to mitigate for the condition.

    In grid AC to AC connections, the grid frequency of 60 Hz is constant and syncing the generator is simple by simply leading the load. No need for variable frequency feedback loops.


  152. 152
    Oklahoma Generator

     

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    Nov 25th, 2009 (5:54 am)

    wow, this is a dream come true and i really like to test this out at the road.


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    Serpent2

     

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    Nov 25th, 2009 (11:53 am)

    I vote for the “hybrid” button that operates more like the prius.. but using the battery for passing and going up hills while the generator supplies the energy for maintaining the cruise control speed..

    I drive an avalanche and would love it to be hybrid’ized so it stayes in 4cyl mode while I go up hills on the highway, or at a stop (or shutting off for that matter) , instead of 8cly mode.. I see the volt operating in the same way with it keeping the generator running at high rpms because it is always at a low soc


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    David Kelsey

     

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    Nov 25th, 2009 (9:11 pm)

    There seems to be a lot of confusion in the modes the Volt will adopt. Here’s my slant on it. Once the battery is depleted to whatever percentage charge is specified, from that point on, all the drive comes from the ICE. The fact that the ICE will drive the generator which in turn will drive the car simply means it is going to be less efficient than it would be if it drove the wheels directly. If you deplete the battery, the ICE will have to bring it back up to the safe charge level, so the ICE might as well just drive the car in the first place. There is no other source of power besides the ICE, so if it is not going to charge the battery beyond sustaining it, you might as well switch the electrics out of circuit and clutch the ICE to the wheels. Not good for PR, if you want to persuade the public you have an EV, but more practical at the end of the day.


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    jeffhre

     

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    Nov 26th, 2009 (2:41 am)

    David Kelsey: There seems to be a lot of confusion in the modes the Volt will adopt.Here’s my slant on it.Once the battery is depleted to whatever percentage charge is specified, from that point on, all the drive comes from the ICE.The fact thatthe ICE will drive the generator which in turn will drive the car simply means it is going to be less efficient than it would be if it drove the wheels directly.If you deplete the battery, the ICE will have to bring it back up to the safe charge level, so the ICE might as well just drive the car in the first place.There is no other source of power besides the ICE, so if it is not going to charge the battery beyond sustaining it, you might as well switch the electrics out of circuit and clutch the ICE to the wheels.Not good for PR, if you want to persuade the public you have an EV, but more practical at the end of the day.  

    You say “might as well” can you please explain how that works, including the transmission that will be newly required, which the “clutch the ICE to the wheels” will engage. And will that have an effect on anything other than price during the operation of the car?


  156. 156
    wwskinn3

     

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    Nov 26th, 2009 (10:10 am)

    #81 Jackson said “. . .Anybody know what Vanadium costs, or where in the world it’s found besides in Australia?”

    A company called URANIUM STAR (URST.OB) just recently announced that they have found what might be the worlds biggest supply of Vanadium in Madagascar (I’m not exactly sure where that is. I have read that Vanadium is essential in the magnets of the electric motors they use – stock is selling at about .55 per share.


  157. 157
    David Kelsey

     

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    Nov 26th, 2009 (11:16 am)

    jeffhre: You say “might as well” can you please explain how that works, including the transmission that will be newly required, which the “clutch the ICE to the wheels” will engage. And will that have an effect on anything other than price during the operation of the car?

    One way might be to drive two front wheel motors on the battery, and when that runs out at 40 miles, cut out the electrics and drive the rear wheels by a conventional axle and crown wheel and pinion, choosing one that is already in production or has been sold in the millions.

    This forum, 156 posts of it, seems to be agonising about how the CS will work. So do away with it for simplicity’s sake. It doesn’t appear to do anything much – it doesn’t charge the battery beyond the minimum – but needs an awful lot of circuitry and complication for very little purpose.

    This could still be called an EV, and will still cater for the large percentage of people that will find the 40 miles adequate. The ICE will be running in either case, and if it isn’t passing its power through a generator, it will be more efficient.

    Cost? Minimal, I suggest, as the bits must be very cheap by now, and all the designing and fretting over the CS vanishes. The car could be put on the road with reliable parts in double quick time – just in time to coincide with the collapse of the man made global warming scam. Technically, the car would be pretty standard, but it was never intended to compete with Ferraris, and for most people, 100 mph is sufficient under speed limits of around 50 mph. Those people won’t care how it works, so long as it does.


  158. 158
    David Kelsey

     

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    Nov 27th, 2009 (1:51 pm)

    Alternatively, put a Mini engine crosswise in the front, driving wheel motors and a generator, battery in the back, motors can also drive the front wheels on electric only for 40 miles, then Mini engine is clutched in and drives the front wheels without assistance from the battery. Or do away with the generator and forget charging the battery. To avoid rotating the engine when it is not running, the wheels would need clutches in their centres. There doesn’t seem to be any need for charging at all, since the best it can do is keep the battery at a safe low state. You would have to think up a new name for this vehicle, since it is not really a hybrid but a twin engine.

    The mode is electric alone up to 40 mph, then ICE alone for as long as you want to. What’s not to like?


  159. 159
    David Kelsey

     

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    Nov 29th, 2009 (12:52 pm)

    Addendum to 158. You could fit an option switch that would allow the electric motors and the ICE to run together, giving sports car performance for the 40 miles. All that and guilt-free motoring too.