How the Chevy Volt Operates Past the Customer Depletion Point
The way the Volt is designed, the first 40 miles of driving are powered by the electric energy stored in the battery. After that distance from full charge, somewhere around 30% state of charge, the on-board generator kicks in. The generator’s job is to keep the battery at that 30% level all the way until the driver can get to where he or she will begin charging again. That level is called the “customer depletion point”. Below is Volt chief engineer Andrew Farah explaining how the Volt will behave at and beyond that level.
How will the vehicle’s propulsion system work when you get to the customer depletion point?
When you get to the customer depletion point, the engine will come on seamlessly as it’s supposed to. But when the engine comes on to spin the generator, it does so with the idea that we’re generating electric energy to drive the wheels, not to charge the battery. People say the engine comes on to charge the battery, but that’s not what really goes on. The engine comes on to make enough electric energy to turn the wheels, because the wheels are always turning electrically.
Now comes the fun part. Remember the electric generator is about half the size of the motor. So you say, how come you don’t have performance problems if you’re trying to go up a hill with only basically half the power capability? That’s where the battery comes back into play. Because the customer depletion point is not full depletion, there’s still energy available. That’s by design. The idea is during certain other peak situations such as climbing a hill or merging into traffic, you will actually take some more energy out of the battery. So you may actually come down a little bit below customer depletion level.
And then when you take your foot off the gas, as an example when you’re done doing the merge, we had taken a little bit out and the battery has a little less in it. So what we’ll do then is we will opportunistically put that energy back into the battery either through regenerative braking or if we have to we will take some of the energy that’s not needed to turn the wheels and bring the battery up to the customer depletion level.
So we don’t recharge the battery. The customer wont actually see any of this, as their electric range indicator in the car will only say zero.
We are actually using that battery at that point as a peak buffer and we will keep trying to recapture energy as the opportunities allow.
Is the customer depletion point going to be exactly 30% state of charge (SOC)?
We are continuing to tweak and tune and develop exactly what that number is.
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Related posts:
- How Charging of the Battery Works in the Chevy Volt
- Will the Chevy Volt Have a “Limp Home” Mode?
- Latest Chevy Volt Battery Pack and Generator Details and Clarifications
- NEW FACT: Chevy Volt Generator Starts When Battery Power Hits 50%, Stops Again at 80%
- GM Has Decided on the 1.4 L 4-Cylinder Engine as the Range Extender for the Chevy Volt
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August 25th, 2008 at 5:59 am
Cool. So we can deplete the battery slightly below 30% SOC and the car will bring it back up to 30% SOC. I’m curious. What was the reason why they can’t charge the battery up to 80% SOC with the ICE? I honestly can’t remember the reason.
August 25th, 2008 at 6:22 am
Rashid -
You don’t want to use the ICE to recharge the battery up to 80% SOC, because that defeats the purpose of a plug-in hybrid: which is to replace the burning of gasoline with electricity as much as possible.
August 25th, 2008 at 6:23 am
Very sophisticated, although it defies a neat summary in today’s “sound-bite” world. They would do themselves a favor by staying away from phrases like “customer depletion point.” But that’s an engineer for you. They need to use language the layman will understand.
But it validates my gut feeling that GM is thinking this vehicle through very carefully.
Oh, and kudos to Lyle for getting this on the record.
August 25th, 2008 at 6:23 am
Customer Depletion Point ?
Who in the hell came up with that Techno Babble phrase ?
August 25th, 2008 at 6:25 am
Rashiid:
I don’t think it is that it can’t be done, it is a decision “NOT” to do it.
Because obviously if you use some of the battery power as a buffer for the generator, and then later the generator or re-gen braking brings the battery back up to 30%, it is recharging the battery.
But the question is: If they have “energy that is not needed to turn the wheels” available, but do not want to charge the battery with it, what are they doing with it? Or will they just shut down the ICE at that point?
Like I said before, it gets complicated…..
August 25th, 2008 at 6:27 am
Rashiid, the reason is simple: that would be economically impractical.
August 25th, 2008 at 6:28 am
I wonder what happens if you deplete the battery to 30% and then start up a large mountain chain with 4 heavy passengers and a clamshell full of luggage on the roof? The battery would be called on for extra power but the regen braking would not make it up.
This is an extreme case but is one that the reviewers will look into when the car arrives.
I would assume that you ultimately loose power down to the ICE/Gen output capacity and then you would be limited in power?
August 25th, 2008 at 6:36 am
#1 Amul
To bring the battery back to 80% SOC would use more gasoline. Also when arriving at your charging station you want your battery in a depleted state to take full advantage of propeling your Volt by means of on-grid electrical energy or alternative electrical energy.
August 25th, 2008 at 6:48 am
Jim @ 5,
But the question is: If they have “energy that is not needed to turn the wheels” available, but do not want to charge the battery with it, what are they doing with it? Or will they just shut down the ICE at that point?
I’ve been wondering about that too. Maybe the ICE will turn at variable RPMs so that only the necessary amount of energy to propel the car and run whatever accessories happen to be turned on is generated. That’s essentially how a normal ICE vehicle works. Regardless of where the battery SOC is, I think that you would always want to recapture energy from the regenerative braking, as that is as close to “free” energy as you are going to get.
August 25th, 2008 at 6:49 am
Lyle,
Great article. This really addresses the heart of how it works.
I wonder if Andrew Farah could tell us more about how the engine behaves. Is it constant RPM or variable RPM? Does the gas engine turn off at low speeds? Will the engine ever turn on above the customer depletion point in order to prevent stale gas and/or make sure the engine still runs?
August 25th, 2008 at 6:53 am
#9 MDDave Says: “Maybe the ICE will turn at variable RPMs so that only the necessary amount of energy to propel the car and run whatever accessories happen to be turned on is generated. Regardless of where the battery SOC is, I think that you would always want to recapture energy from the regenerative braking, as that is as close to “free” energy as you are going to get.”
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With either constant or variable RPM engine designs, the gas engine output can be varied to accommodate a varying load. With a constant RPM engine, the fuel mixture is varied.
When regenerative braking occurs, the engine output will be reduced dramatically, or perhaps the engine will even be shut off.
August 25th, 2008 at 6:54 am
7 Nuclearboy:
There is actually a perfect testing scenario for that. I-40 from Tennessee heading to Asheville.
24 miles of switchbacks and inclines. from West-East Tenn-Asheville there are no declines. It is all uphill.
This is also the area that BMW uses to test their cars handling for the states and I think they also used it to test the Corvette.
August 25th, 2008 at 6:57 am
#5 jim, I was thinking the same thing as you.
Does the engine actually shut off if you are in ICE mode? Let’s assume you just went up a big hill in ICE mode and are down to %25 now you are sitting in the parking lot with the AC on. After reading the article I get the impression that the ice will run the AC and charge the battery up to %30. Now, at %30 you still have the AC on, so does the ICE
A. Stay on to keep the AC going and continue to charge the battery with the remaining power. And if so to what percent will it do this?
B. Stay on to keep the AC going but waste the extra electricity.
C. turn off and let the battery power the AC for some time down to say %25 and then the ICE will kick back on
D. Turn off and let the battery run the AC untill the battery is dead.
Personally I think there needs to be a range say %25 to %35 that when the battery gets below %25 the ICE will stay on and power the car and charge the batt until it gets up to %35. At %35 you are back to straight battery. A range like that won’t have your engine charging the battery needlessly and won’t be wasting electricity. The article just seemed a little ambiguous and clarification would be helpful.
August 25th, 2008 at 7:02 am
About the variable RPM stuff, I thought we were told that the engine would be constantly running at it’s peak operating RPM constantly. Maybe I got that wrong but that was the impression I got. After reading this article it seems to me that the peak RPM efficiency is probably matched up with the maximum generating capacity of the generator. If that is the case, more RPM’s wouldn’t translate into more energy for the battery. But that also means if only a little energy is needed, you are either charging the battery too or wasting the extra energy.
Hey Lyle, thanks for the monday morning mental stimulation!
August 25th, 2008 at 7:09 am
This is about how I thought it would work.
Nuclearboy #7 - I brought this up some months ago but added headlights, wipers and HVAC to the equation. I guess there will be a point at which these factors could affect performance just as they do in an ICE powered vehicle. I once owned one of those small motor homes on a Toyota chassis. Had a 4 cylinder engine which was adequate about 90% of the time. But if you were in the mountains or had a head wind then there were issues.
August 25th, 2008 at 7:12 am
The 80% limit (and 20% low limit) is there because lithium batteries are damaged slightly when they’re either fully charged or fully depleted.
The limits aren’t economical or environmental, it’s to extend the life of the battery.
August 25th, 2008 at 7:13 am
I find Farah’s explanation very confusing.
I also have to wonder what happens to the car if you run into a situation where your power demand is large and sustained for a long period of time. It takes a lot of juice to climb the Rockies… what happens if you leave Denver after driving around for 40 miles and depleting the battery, then head into the hills? Climbing takes a lot of power. Will a 1.4L engine provide enough electricity to keep the battery from becoming severely depleted?
August 25th, 2008 at 7:22 am
I don’t care what they call it for now…..as long it works. The Volt is only in the building stage and by the time the car gets in the customers hand, the wording in the manual will have been carefully scrutinized.
August 25th, 2008 at 7:24 am
Oh my heart be still…. the posted pic is an EV1 dash!
It’s cool to see the power up sequence.
http://www.youtube.com/watch?v=bsdUfAEIEos
To the point… I’m glad they finally cleared up the phrase “charge the battery”, very misleading, confusing etc…
The engine may very well always run at a constant speed with loading added or removed via the power electronics, not speed the engine up or down. A standard run of the mill power generator works that way, it doesn’t slow down or speed up based on load… the engine powering a generator tries to maintain a constant speed, feeding more gas to the engine as the load increases, less gas as the load decreases. The goal in an AC generator is to maintain cycles per second. Just my opinion… they could have it vary it’s speed but I doubt it. We had an ac generator that would drop to idle if it detected no load and then quickly speed up to running speed when a load was detected.
August 25th, 2008 at 7:31 am
If you vary the speed of gas engine, you now are taking it out of the “sweet spot” which in the previous article was the reason you could get such great efficiency (see 50mpg article)
August 25th, 2008 at 7:33 am
#2 capricorn, #5 Jim I, #6 Alexander, #8 Dick G,
Thanks for the responses.
I should have been more descriptive in my question.
I was thinking of a long highway trip of several hundred miles.
I would get the first 40 from the plug-in and the rest from the ICE.
Would it make sense that while the ICE was running, to charge the battery to 80% SOC and then shut off again. I would get the next 40 miles on battery alone, then the ICE turns on, charges to 80% SOC, turns off and I get the next 40 …………………. You get the picture.
This scenario, for me anyway, supports Jim I’s question in #5.
August 25th, 2008 at 7:34 am
My first impression of this was…gee, I hope they arent overthinking this….
but looking at the big picture…I’ll agree w/ #3, they are being careful and thorough here… you’ve got to be able to make that battery last and use that ICE as efficiently as possible.
As a layman — I actually follow this logic and at the same time agree that the term “Customer Depletion Point” doesnt have to be so fancy — how about “Bettery Charge Level” ?
August 25th, 2008 at 7:35 am
I have seen little talk about the actual genset itself. The gas part of the motor matters little. It is the generator part that matters what is that configuration?
gensets run at certain rpms to generate certain levels of electricity, as the load increases they up the RPM’s, however even gensets are not supposed run at full throttle for extended periods of time.
It would seem very practical to run everything at a certain rpm and then dip into the battery for certain levels of surge.
my guess is that they can spin the generator up to a certain level and then would need to go to the battery for max RPM’s.
anything over redline you could not sustain for very long with any engine.
GM is a car company so the know the tests.
I mean if i lived in colorado i doubt i would buy a 4 cylinder motor home as described!!
tomatolord
August 25th, 2008 at 7:37 am
LyleL #19.
Thanks for the link.
I had no idea one could hear the whine of the electric motor on the EV-1. I wonder if the Volt will be that loud. I was expecting no noise at all.
August 25th, 2008 at 7:39 am
So its exactly as others on this blog have surmised. Still its good to see it written down.
GsNed57.
I would expect the motor/generator to cycle on and off as needed.
August 25th, 2008 at 7:40 am
This sounds very complex…how simple it sounds to make a BEV Volt. No E-REV, generator, etc. Once you’re out of juice, you’re out. Maintenance is much simpler. Volt 2.0 should be a BEV!
August 25th, 2008 at 7:49 am
To me, there may be scenarios where you’re not using all the energy that the generator is creating to drive the vehicle. In those cases, that energy should be put back into the battery, even if it charges it all the way to 80% SOC.
Since the generator will always be on after you reach 80% SOC, why not take advantage of any extra energy being generated? The gas is getting burned anyway.
I’m not saying run the generator harder to charge the batteries, just to take whatever energy is available, if it’s avialable, when the generator is running at its lowest level, and stick it into the battery.
August 25th, 2008 at 7:52 am
Actually, the Fisker Karma has a rtechnique similar, but more pronounced : by swithc the car to “High performance,” both the battery AND the generator supply power, in this case to provide fast acceleration, rather than any need for hill-climbing, as in the Volt instance. When the Vette goes plug-in, look for this feature.
August 25th, 2008 at 7:57 am
I think the driver should be given the decision of how to use the battery when driving long distances. The drive should be able to select long range or normal. Normal being the above described mode and Long range would drain the battery based on demand and to maximize fuel savings with the ICE. If you added in some info from the driver like distance to be driven imputed to the computer that controls the ICE then you could use the battery to best advantage. This car begs for this type of control. We should not think of this as a battery only car. Real world driving means that we do drive long distances.
August 25th, 2008 at 7:58 am
That explaination was certainly unexpected.
If what Mr. Farah says is correct, then the engine/generator needs to produce enough juice to power the vehicle at all speeds and grade inclinations; all of this while having the engine operate within a relatively narrow RPM range.
Secondly, according to the MotorTrend SOC chart, the engine periodically shuts off during “charge sustaining mode”. If the engine shuts off, how can the generator power the electric motor during charge sustaining mode ?
And, why do they call it “charge sustaining mode” when the battery really isn’t being charged ?
August 25th, 2008 at 7:59 am
I think there is a misconception about running the generator and what happens to the juice if not needed by the car at somepoints . The juice will flow into the battery, not be “dumped on the floo” as
some think. The system doesn’t try to always maintain a charge at ‘exactly” 30%, that would be a silly thing to do, even if you could do it (you can’t).
August 25th, 2008 at 8:08 am
#27 Eric C.:
“that energy should be put back into the battery, even if it charges it all the way to 80% SOC.”
Once you get to, e.g. 40% of SOC or whatever, then turn the ICE off and run back down to 30% SOC on pure electric. If you’re going I-40 westbound from Asheville, downhill into Tennessee, and regen gives you 80% for free, then by all means take it.
This article is making me wonder if I may have been wrong about throttle position on the 50 MPG thread. In any case, I would bet GM will figure out what scenario is the best in a given circumstance and program it into the system. I’m still guessing the ICE will cycle on and off sometimes.
August 25th, 2008 at 8:09 am
A couple of points. Electrical generators can be configured so they generate more power as RPM increases, like the old bicycle generators we used as kids. They can also be configured to produce more power as speed remains constant but torque increases.
Yes, if because of a long period of hill climbing at high speed, you used up the battery capacity reserved for charge sustaining mode of operation, performance would drop off. Instead of using up to 120 KW, you would be only able to use up to 53 KW. But you could still get where you were going, only at a lower speed. But this circumstance seems rather hypothetical, because the design envelope will be able to handle the typical grades we encounter on an interstate with no performance degradation.
August 25th, 2008 at 8:10 am
#31 Kent, This quote is what makes us question what happens to the extra energy once the battery is at %30 and you are running in ICE mode.
“And then when you take your foot off the gas, as an example when you’re done doing the merge, we had taken a little bit out and the battery has a little less in it. So what we’ll do then is we will opportunistically put that energy back into the battery either through regenerative braking or if we have to we will take some of the energy that’s not needed to turn the wheels and bring the battery up to the customer depletion level.”
He’s talking about bringing the charge back up to the CDL. But then he goes on to say they aren’t recharging the battery. Just a little confusing, but I think I understand what he’s getting at
August 25th, 2008 at 8:10 am
Well, thank you for all your thoughts and comments. There is a lot of sense in them. But I think that even if Lyle got a very good info from A. Farah this is definitively not the whole story, we have to be patient and continue to ask what we think that is important.
JC
August 25th, 2008 at 8:17 am
I think it’s a red herring to discuss what the Volt should do with the extra energy being generated (store it or dump it?).
Sure the Volt might generate a few extra watts here and there but it’s I really doubt it’s going to be generating so much power than it could actually charge the battery up. I would imagine GM will have an intelligent system that says ‘whoa, we’re generating 25% more power than needed. Let’s turn the generator down a few notches’.
GM is going to have some way of controlling the power output of the generator (whether that’s through variable RPM or variable throttle position). It seems only logical that the Volt will be regularly adjusting the output of the ICE to match the generators needs. Accordingly, there might be a temporary surplus of power that gets you to 32%. It would be silly to dump the power (waste it) or to store the power (lose opportunity to charge electrically) when a simple solution like turn down the generator exists. I think we can assume they’ll do this and the real question is how.
August 25th, 2008 at 8:18 am
_____________________________________________________
The VOLT program is without a doubt helping GM gain a stronger industry leadership position both in terms of meaningful innovation and positive consumer perception. This will result in more cars sold.
Here is another opportunity for GM to demonstrate industry leadership:
GM should consider being the first automaker to announce that they are making a PV Cabin Exhaust standard on ALL GM cars. If GM did this, it would force other automakers to follow suite and GM would be positively credited with setting this standard. GM should take the opportunity to do this before some other large automaker takes the lead on this item. It is also just simply the right thing to do.
Here is today’s reason for PV Cabin Exhaust as a standard feature:
http://www.foxnews.com/story/0,2933,409721,00.html
I have heard the argument on this blog site and other venues that a PV Cabin Exhaust will invite additional child-left-in-car deaths due to people intentionally leaving children in cars because they will assume the PV Cabin Exhaust will keep the children safe from over-heating. This erroneous argument is similar to arguing that we are better off not having air-bags in cars because in encourages people to drive more recklessly. Are we better off without ABS brakes and seat belts? How about removing engineered crumple zones because it fools us into a sense of security?
Placing a PV Cabin Exhaust on all GM cars as a standard feature will drive the per unite implementation cost way down and will be a very positive selling feature especially for those prospective customers tired of getting into “oven” cars during the summer months (think Florida, Georgia, Texas, Arizona, Nevada, etc…).
A PV Cabin Exhaust as a standard feature would be a tipping feature for me any many other car buyers.
_____________________________________________________
August 25th, 2008 at 8:19 am
#7 nuclearboy asks: “I wonder what happens if you deplete the battery to 30% and then start up a large mountain chain with 4 heavy passengers and a clamshell full of luggage on the roof? The battery would be called on for extra power but the regen braking would not make it up.”
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Sure, I can answer this with some simple math.
We know that the gas engine generator’s maximum output is around 53 Kw. For the peak power from the electric motor, we’ve heard numbers of 100 Kw and 120 Kw, so let’s call it about 110 Kw. This means that when you floor it uphill, the batteries will have to produce about 57 Kw.
We know that the total energy storage of the battery pack is 16 KWh, so if the customer depletion point is 30% SOC, that would be 4.8 KWh. So the amount of time the Volt can deliver peak power would be 4.8 KWh / 57 Kw.
Bottom line: if you constantly floor it uphill, you’ll be able to go around 5 minutes before the batteries completely drain and you lose peak power.
Note that this assumes that there are no level or downhill parts of the grade and you’re flooring it all the way. If there are downhill parts of the grade, the extra weight in the vehicle would make regen braking work better.
So this corresponds to a very long steep mountain road, something like a 5 mile 6% grade. The only such road I know of is going west out of Death Valley, CA. In this case, there are pull-off areas with running water to cool off your radiator, or if you’re going down hill, so you’re brakes can cool down. The point is that regular cars also have problems on such grades, so the Volt is not alone here.
August 25th, 2008 at 8:25 am
Re: post 17, dagwood55, et al…..
Question: Could a Volt weighing 4,000 Lbs including passengers climb a (steep) 6% grade up a 10,000 ft mountain using only ice/gen power?
Answer (approximation):
Power(Hp) = [F(lbs) x V(mph)]/375* = (4,000lbs x 4.2mph**)/375
= 44.8 Hp (….or 44.8 x 746 = 33.4Kw)
Therefore, a Volt should be able to climb a steep mountain (6% grade) at a steady speed of 70 mph, with reserve power & without need for battery assist. Since there is an ample power margin, a climb of 10,000 ft should be achievable even at 70 mph.
**(Assumes the velocity is 70mph up a 6% grade, so the vertical velocity would be 6% x 70mph = 4.2mph)
*375 is a constant for force in pound feet & velocity in miles/hr
August 25th, 2008 at 8:27 am
#36 Dan Says: “GM is going to have some way of controlling the power output of the generator (whether that’s through variable RPM or variable throttle position). It seems only logical that the Volt will be regularly adjusting the output of the ICE to match the generators needs.”
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Yes, GM said this last summer:
http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/
Also, just as you say, there is no wasted electricity. If the ICE/genset temporarily generates more power than required, it will charge the battery very slightly, and then the ICE output will be decreased to discharge the battery very slightly, maybe a couple of percentage points around the customer depletion point.
August 25th, 2008 at 8:29 am
Okay, this may be a dumb question, but if the depletion point is 30%, then is the all electric range somewhere around 28 miles (40 mile all electric range minus 30% of 40 miles (12) ?
August 25th, 2008 at 8:32 am
Did we all read a different post?
Where does it actually say that the generator won’t stay on until 80% SOC?
All-in-all, a nice glossing over of some of the major problems with the Volt design (i.e. hauling around 1/3 of the battery that you never really get to use in all-electric mode).
On the flip side, if they are not getting the range they want, I am pretty sure that 30% will become 25% or 20% to make up the difference.
August 25th, 2008 at 8:32 am
#39 nasaman,
If this is true, then the Volt is over-designed.
Do your numbers account for aero or rolling resistance? Would this be significant? Are there other factors?
August 25th, 2008 at 8:33 am
Regarding the conversation on how the Volt will handle extended climbs (i.e. I-40). It seems to me that even crossing the rockies in a fully loaded down Volt is not going to require (on average) more power than the 1.4L engine can generate (on average). It’s not like it requires full throttle at all times to cross the rockies.
I bet GM has figured out what the highest sustained power draw is that you could expect to encounter and it has made the ICE capable of delivering that indefinately. In other threads, poster have provided info on the HP required to cruise around 60-70mph. If I recall correctly it was around 20-30hp. Accordingly, I can’t imagine you’d need an average higher than 50-70hp to climb a mountain pass.
Maybe I’m wrong and if so, once your battery was depleted to the ultimate cut off point (20%?) then you’d simply be limited to the power output of the ICE which is what, 80-90hp?
August 25th, 2008 at 8:33 am
(PS: My calculations in post #39 are an approximation because they neglect the Hp needed to propel the Volt on a horizontal road; however, I would estimate the Hp needed to move the Volt at a steady 70mph on a flat surface would be <20, so the conclusion of post #39 should still be OK or very close to OK)
August 25th, 2008 at 8:36 am
#41 benson asks: “Okay, this may be a dumb question, but if the depletion point is 30%, then is the all electric range somewhere around 28 miles (40 mile all electric range minus 30% of 40 miles (12) ?”
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The 40 miles AER only represents 1/2 of the available energy in the battery. See here for details:
http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/
By the way, the figure of 28 miles is important. This is about how long you can run on batteries after you run out of gas.
August 25th, 2008 at 8:41 am
Two points:
1) There must be a deadband around the targeted 30% SOC.
2) GM should allow operating mode selection by the driver.
1) Deadbands are used to eliminate inefficient starting and stopping of the range extending engine (say 30% to start and 35% to stop). GM is certainly testing different deadband widths against different driving scenarios. No one approach can effectively fit all use cases.
2) If GM would mistakenly only support one approach, say the more general one described above, then an owner who reaches the foot of the Appalachians or the Rockies at 30% SOC will conclude that the Volt is a worthless piece of trash. The vehicle will quickly exhaust its remaining charge as it begins to climb and then will slowly crawl along in the truck lane in a patheticly embarassing manner. By the time the owner eventually reaches the top of the climb, they will likely start looking for a cliff to shove it off, and I wouldn’t blame them.
Instead, GM should offer the driver a selection of operating modes so that they can “inform” the car of the expected use case for that drive. In this way, an “energy saving” operating mode like the one described above (flat, start and stop, low speed) will still be available to produce exceptional efficiency.
On the other hand, a “power intense” operating mode (hills and mountains, constant high speed, racing) could be available when needed. This latter operating mode might attempt to keep the battery fully charged (80% SOC) at all time using the range extending engine. This would give the Volt the best chance of keeping up with other traffic along the entire hill climb.
These operating mode selections should be able to be changed easily by the driver while the car is in motion. Displays should reflect which mode the car is in, and how well the operating mode targets are being maintained (an infinitely long hill climb will still eventually drain the Volt’s battery). In this manner, the new Volt will appeal to a much larger audience across all regions of the U.S.
August 25th, 2008 at 8:42 am
#44 Dan Says: “Regarding the conversation on how the Volt will handle extended climbs (i.e. I-40). It seems to me that even crossing the rockies in a fully loaded down Volt is not going to require (on average) more power than the 1.4L engine can generate (on average).”
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Three points:
1) It’s not the average, but the peak power required for long constant uphill grades that may be a problem.
2) The 1.4L engine in the Volt is tuned for efficiency, not power. It will use an Atkinson cycle and only generate around 70hp max. The remaining peak hp comes from the batteries.
3) I believe the I-40 example includes many level and downhill sections where the batteries can recharge.
August 25th, 2008 at 8:49 am
The scenario Volt chief engineer Andrew Farah described makes sense for commuter situations, where one is close to home where the Volt can be recharged. But, what does he say about long highway trips described by #21 Rashiid Amul?
I agree with Rashiid when he said “It would it make sense that while the ICE was running, to charge the battery to 80% SOC and then shut off again. I would get the next 40 miles on battery alone, then the ICE turns on, charges to 80% SOC, turns off and I get the next 40 …………………. You get the picture.”
#47 hermant makes a good point. I would add long trips to his list of operating modes.
August 25th, 2008 at 8:55 am
you should have the option (switch) to recharge the battery fully if you want to. If you were going on a longer trip you may want to leave the engine runing to complete the charge.
August 25th, 2008 at 9:00 am
I raised the issue several months ago about the repetitive starting of the Volt ICE (particularly on long trips with the scenario described by Andrew Farah) and the long term effect that it will have on the ICE, but never got an answer.
Perhaps one of the ICE engineers might care to comment.
August 25th, 2008 at 9:02 am
I agree with #50 Dale, assuming “complete the charge” is to 80% SOC.
I would envision the “operating mode” option being set through the touch screeen rather than a manual switch.
August 25th, 2008 at 9:02 am
capricorn Says: @2
I believe you hit it right on the nose. If the motor/generator is capable of maintaining the battery at about 30%, that’s the way to go to gain full advantage of a plug-in.
August 25th, 2008 at 9:04 am
It seems to me that GM wants to limit the number of charge cycles during the battery pack’s lifetime, thus not allowing the ICE to charge the battery once the customer depletion point is reached. Now, the batteries will have only one or two charge cycles per roundtrip instead of several cycles that will effectively lower the battery life. GM is heavily protecting the degradation of the battery…
As for the mountain discussion, yes, uphill is a concern yet I am confident that GM will address this issue. When I worked in the automotive industry, every vehicle I was a part of was tested in the Rockies in order to calibrate the ECU for the high altitude. So, designing for the mountain terrain has always been a must in all cars. Another thing to add is that the MPG will be significantly lower when coming back down the mountain with regenerative braking and coasting. I wonder if the ICE will come on at all at some points when my Volt is rolling down the mountains back to Denver….
August 25th, 2008 at 9:14 am
#54 Aspherical said:
It seems to me that GM wants to limit the number of charge cycles during the battery pack’s lifetime, thus not allowing the ICE to charge the battery once the customer depletion point is reached.
______
Perhaps I had misunderstood, but isn’t it GM’s goal to limit the lifetime number of charges to 100% SOC rather than limiting the number of charge cycles?
August 25th, 2008 at 9:14 am
#42 GXT
“All-in-all, a nice glossing over of some of the major problems with the Volt design (i.e. hauling around 1/3 of the battery that you never really get to use in all-electric mode).”
From what I’ve read, not using 1/3 of the battery is necessary for a long battery life. Using all of the battery’s stored energy would not be in your long-term best interest.
August 25th, 2008 at 9:21 am
The term customer depletion point must be a carry over from the decisions to close some of the pickup plants, try to sell the Hummer line, and sell the midsize truck line to Navistar.
August 25th, 2008 at 9:25 am
#56 ThombDbhomb
Isn’t it the “deep discharges” to/near 0% SOC and the number of “full” charges to 100% SOC that have a long term negative effect upon the battery life?
I don’t recall reading that multiple charging cyles to keep the battery between the approximate range of 30% SOC and 80% SOC as having a long term negative effect upon the barrery life.
I might be wrong on that. If so, perhaps others can clarify that point.
August 25th, 2008 at 9:27 am
I think we will have to wait to see the different modes they end up using. The battery will be part of the circuit when the generator is running. They will try to match the generator as close to the motor demand as possible but any extra output will be used to charge the battery just like any sudden motor demand will discharge the battery.
I wish they would show a graph of where all the energy is going like they do for the Prius. Even if it’s not the default screen, us technical types want to know everything!
August 25th, 2008 at 9:34 am
I have read this entire thread. There is still confusion here. One of the very last posts still advocates using the ICE on long trips to charge the battery. Here is my take for what it is worth.
In over 99% of the cases, using the ICE to charge the battery makes no sense. To extend the range, you run the ICE, but since a HPhr of energy generated by the ICE costs about 3 times as much as a HPhr of energy drawn from the battery, you want to run the ICE as little as possible, and arrive back home with a battery depleted down to 20-30%. You then charge it up with cheap electricity, rather than using expensive gas to charge the battery.
In other words, you run electric for 40 miles or so. When the battery gets down to 30%, the ICE kicks in, and runs at constant RPM. If you are driving on the level, or with balanced ups and downs, the ICE generates surplus power, which goes into the battery. If you generate enough surplus power, the battery will charge up to some setpoint, programmed into the computer by GM, say 35%. At this point, the ICE should shut down until the battery gets down to 30%. To keep running the ICE just to charge the battery is a waste of expensive gasoline.
The one exception which looks to me like it could be legit, is what if you are facing a trip over the Smokeys or the Rockies, or some other extremely long uphill pull. The above scenario would still work, but if you ran the battery down to the point where you could draw no more power, the car’s HP output would be limited to that of the 1.4l ICE, with no surge assist from the battery. In other words, the car would slow down on very steep hills, and accelerate sluggishly.
This is not a disaster, but GM may be working to quantify this effect, and determine if it is worthwhile to provide a “build reserve charge” mode. This would be needed only in extreme cases, and would require some foresight. The driver would need to recognize the need to build extra charge while driving to the foot of the mountain, and invoke the “build reserve charge” mode. Futuristically, the GPS could interface with the car’s computer, and do this based on destination, and known distance and elevation changes.
But if you invoke the “build reserve charge” mode when you don’t need it, you will waste a lot of gas. This is because you will run the ICE to build up a charge which stays in the battery until you get home, and you find yourself at home with an 80% battery charge built up with expensive gasoline, that you can now do much more cheaply by plugging in to the grid.
August 25th, 2008 at 9:38 am
I don’t think the number of charge cycles of the batteries are going to be an issue. As with Cell phones … people either will plug them into the chargers all the time / as often as possible … to keep a “full” charge …. or…. they run them right down…then plug in..
I will be plugging my Volt in every time I return to the office… I am in and out a 1/2 dozen times a day… short runs (5 KMS) and longer runs (up to 160 KMS) … and this is every day… For me to maximize the benifits of the batttery …. I will want it always “topped up”..
August 25th, 2008 at 9:41 am
Very good article Lyle.
So there will be parallel electrical paths.
1 - Engine to battery to wheels
2 - Engine to wheels
Anytime you go through the battery, there’s a charge-discharge efficiency loss so you’d prefer to skip this whenever possible. This method makes sense to me. Great job GM.
August 25th, 2008 at 9:42 am
#59 Texas said:
The battery will be part of the circuit when the generator is running. They will try to match the generator as close to the motor demand as possible but any extra output will be used to charge the battery just like any sudden motor demand will discharge the battery.
_____
This suggest that some of the generator output will be sent directly to the electric motors, bypassing the battery. I recall hearing this speculation before but don’t recall GM specifically stating this is as fact.
If it is otherwise and 100% of the generator output goes to the battery, then everytime the ICE starts it results in a battery charge cycle, even though the charge might be small and of short duration.
August 25th, 2008 at 9:44 am
#58 Estero
That was the point I was trying to make to GXT. You and I agree.
August 25th, 2008 at 9:53 am
Andrew Farah said:
Q: How will the vehicle’s propulsion system work when you get to the customer depletion point?
A: When you get to the customer depletion point, the engine will come on seamlessly as it’s supposed to…The engine comes on to make enough electric energy to turn the wheels, because the wheels are always turning electrically.
_____
If the above is true then doesn’t it mean the ICE will run indefinitely once it comes on? Or, am I missing something here?
August 25th, 2008 at 9:57 am
As long as I can use the Volt for emergency backup power for my home, to power tools in the field or on my camping trip, I’m happy.
I can’t……
(nevermind)
by the way, here is an EXCELLENT video about Digital Rights Management– or what ZDNet Executive Editor David Berlind calls C.R.A.P. (Content Restriction Annulment Protection) — has enabled companies like Apple to lock music downloaded through their service into their own devices. Berlind describes an effort to create a DRM standard so content can flow seamlessly between multiple devices.
http://www.youtube.com/watch?v=Ww65z8HuIJ8&feature=user
If Apple sets the standard as I-Pod, they also set the (high) price of the media content. “DANGER Will Robinson…”
August 25th, 2008 at 10:03 am
#42 GXT said:
Where does it actually say that the generator won’t stay on until 80% SOC?
_____
It wasn’t mentioned in this interview with Andrew Farah. But, the charge range was mentioned in another interview several months back.
#64 ThombDbhomb
We do agree. Now, I’m interesting in hearing what others have to say about my #65 posting.
August 25th, 2008 at 10:09 am
Does that mean if you are at 30% Battery and the ICE is running, but it stops running at a red light?
August 25th, 2008 at 10:12 am
This begs the question, “If you have a propulsion system in which a small efficient gasoline engine powers an onboard generator which in turn supplies electrical energy to an electric motor to propel the car at 50 mpg, why would you not employ this system as a mainline powerplant without the expensive batteries?
Of course you would need a few batteries perhaps to help with peak power load conditions, but nothing on the scale of 40 miles AER.
This is the same principle behind diesel/electric locomotives. It would seem that GM is in the process of perfecting that system for automobiles. Is their something they are not telling us? Are they actually planning on rolling this out as “e-flex light” in other production vehicle(s)?
August 25th, 2008 at 10:13 am
#45 nasaman Says: “(PS: My calculations in post #39 are an approximation because they neglect the Hp needed to propel the Volt on a horizontal road; however, I would estimate the Hp needed to move the Volt at a steady 70mph on a flat surface would be <20, so the conclusion of post #39 should still be OK or very close to OK)”
————————————————————————————–
Actually, GM said last summer that “Peak efficiency (of the ICE) will be at around 30 kW, which is what the car should require at 65 mph slightly uphill, although the actuals of mass and energy requirements are not final yet.”:
http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/
Given that the mass seems to have increased, and the aero seems a bit worse than expected, I would say 30Kw for 70mph on level ground is about right.
August 25th, 2008 at 10:15 am
If I wanted a pure EV with a 68 mile range could I just run without gasoline?
August 25th, 2008 at 10:17 am
This article gets me to question how the batteries are segmented. Once the customer depletion point is reached, will only a certain segment of the battery pack be charged (to 80%, for example) by the generator to run the wheels, leaving the other plug-in segment of the battery pack at 30% to preserve the life? We have been treating the battery pack as if it was a giant AA battery. I would be interested in knowing how the battery pack is segregated internally. This could answer alot of questions in this post.
August 25th, 2008 at 10:17 am
#69 Voltme
Hmm, a pure gas/electric Volt sounds interesting.
I agree, if you can do without the 40 mile AER, why not just toss the battery and add a little larger generator ?
Am I the only one that would like to see the price of this car reduced by $10,000 ?
August 25th, 2008 at 10:20 am
The primary confusion is whether the ICE will run at constant RPM. I have seen conflicting answers and support info for each. Does anyone have the definative word on this?
Otherwise the question by KUD @ 68 is a good one.
August 25th, 2008 at 10:21 am
#69 Voltme Says: “This begs the question, “If you have a propulsion system in which a small efficient gasoline engine powers an onboard generator which in turn supplies electrical energy to an electric motor to propel the car at 50 mpg, why would you not employ this system as a mainline powerplant without the expensive batteries?”
————————————————————————————–
This question has been asked many times before.
The answer is that you still need a lot of battery power to supply the peak HP. The gas engine only supplies average HP. The electric motor and batteries supply peak HP. So you need a fairly large sized battery pack to make the E-REV (a.k.a. series hybrid) design work, even if don’t need the all-electric range.
August 25th, 2008 at 10:23 am
# 60 Tom Harwick
I think, that „energy intensive mode“or “mountain mode” should not mean 80 % charge. Should be enough 50 % or even 40% when engine kicks in. 5 mile 6% grade is very exceptional case and can be handled by IEC when in the end of elevation little bit slowing car. In case you keep 80% charged battery there will be no room for regenerative braking on downhill. Let’s assume that normal driving capacity on highway is 12 kW (60 mph). I think on the slope average IEC load will be not more than 35 kW. Very short load increase can be when accelerating on the slop uphill and will be handled by the 40% battery reserve.
August 25th, 2008 at 10:28 am
#74 MetrologyFirst asks: “The primary confusion is whether the ICE will run at constant RPM. I have seen conflicting answers and support info for each. Does anyone have the definitive word on this?”
————————————————————————————–
No. There has been no definitive answer on this.
GM said last summer that it would be variable RPM:
http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/
(see last paragraph or article)
And then Bob Lutz just said on the Charlie Rose interview that they were thinking about a single RPM engine:
http://gm-volt.com/2008/08/20/lutz-production-volt-has-a-cd-between-28-and-29-and-battery-extreme-cold-performance-is-good/
(about 7 minutes into interview)
Lyle: Is there any way you could get GM to answer this question?
August 25th, 2008 at 10:31 am
#76 Darius
How much energy is it that can be reclaimed through regenerative braking? I’m sure going down a mountain is different than normal city/highway driving, but I have no feel for the amount under different conditions. What is the formula?
August 25th, 2008 at 10:33 am
Dave G,
You are to pessimistic about 30 kW at 70 mph. In that case 40 miles “all electric” range for Volt s not valid at all.
In that case you can easy calculate “real range” 40 miles x 8 kWh (battery effective capacity) / 30 kW = 18,6 miles (all electric range).
August 25th, 2008 at 10:37 am
I will wait until I see the actual schematics to see how everything is hooked up. Like any marketing guy would know that. Parallel paths for a direct generator to motor connection and then a separate circuit to the battery to handle excessive demand and over generation? I don’t know about that. Again, I will wait to see what they come up with. I’m guessing it will all just be connected. It would be a lot easier and I don’t see a reason for doing any different. The motor will draw what it needs from the circuit and they can match the output from the generator fairly closely (but not perfectly). The net charge on the battery would (could) be very small.
This way they could just change the modes by running the generator harder, longer or both without messing with any multiple circuits. Am I missing something?
August 25th, 2008 at 10:38 am
#71 Belloc asks: “If I wanted a pure EV with a 68 mile range could I just run without gasoline?”
————————————————————————————–
Good question!
From what I understand, it would work that way. When you run out of gas, you still have another 28 miles of battery to get you home or to the gas station.
However, frequently discharging the battery significantly below 30% will wear out the battery much, much faster. So it will become a warranty issue. If you constantly run without any gas in the tank, then when (not if) you have to replace the battery, they will probably check to see how you’ve been using it. If you run it without gas a lot, it will probably void your warranty, and you’ll have to pay the $10,000 for a new battery yourself.
August 25th, 2008 at 10:42 am
#78 Estero,
NASSAMAN calculated that on the 6% slope average capacity need is 33,5 kW. On the flat road (or to cover normal friction) we need 12,5 kW. The difference between those two figures woul be reganarative braking capacity (~20 kW) on the 6% long downhill slope.
I have to leave for now.
August 25th, 2008 at 10:43 am
#32 Fahrvergnugen Fanboy,
I agree that it would make sense to turn the generator off if it reached a higher limit, but I thought GM had previously said it would not turn on and off.
August 25th, 2008 at 10:43 am
#79 Darius Says: “Dave G,
You are to pessimistic about 30 kW at 70 mph. In that case 40 miles “all electric” range for Volt s not valid at all.
In that case you can easy calculate “real range” 40 miles x 8 kWh (battery effective capacity) / 30 kW = 18,6 miles (all electric range).”
————————————————————————————–
That’s true! I didn’t think of that.
So what GM says here doesn’t seem to make sense:
http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/
August 25th, 2008 at 10:46 am
#1 Rashiid - ” What was the reason why they can’t charge the battery up to 80% SOC with the ICE? I honestly can’t remember the reason.”
Greg Woulf #16 has it right that it’s about harming the battery. However, it’s not that the charge would harm the battery, it’s the *number* of charges over the lifetime of the battery pack which are the problem.
A123 claims its battery pack can be cycled 7000 times at 1C before it loses 20% of its capacity. GM can’t count on the 1C discharge, and it would like a margin of safety on the life of the pack, so it wants to limit the cycles below 7000.
Now it’s just arithmetic. With 365 days in a year, if someone charged and discharged once a day you get to 3000 cycles. But the possibility exists that someone (like you) might charge the pack twice in a day — once before going to work and once at work. The possibility also exists that someone like Statik would be doing 90 mph with jackrabbit starts, discharging at over 1C. In these cases you are looking at 7000 cycles, with potentially some of the discharges above 1C.
Given this, the last thing GM wants to do is add cycles on a long trip. For example, if you went 100 miles and the battery was completely discharged and then recharged once during the trip, you’d have two cycles per 100 miles. Do the same on the return trip and you have four cycles per day. Four cycles a day would turn into more than 1000 cycles per year just commuting five days during the week. That would be over 10,000 cycles during a ten year period, way above the limit of 7000.
BTW, the cycle issue is why, if the energy density of the battery doubles, the range could conceivably quadruple.
August 25th, 2008 at 10:47 am
#73 Dazed and Confused,
See post #75.
August 25th, 2008 at 10:48 am
Will the ICE be running all the time after customer depletion point ?
Or will it be off at certian times ?
We know ICE mode graph that GM provided us sometime back says that ICE will be off at certian times. Did this change now ?
August 25th, 2008 at 10:51 am
#85 DonC
I agree. It’s not that the battery can’t be recharged to 80% by the ICE, GM wants to limit the number of cycles of the battery pack. As I stated in post #54, GM is heavily protecting the degradation of the battery…
Now, I am wondering what percentage of the battery pack is “charged” by the generator once the customer depletion point is reached. I am not convinced this battery pack acts as a giant AA battery. I want to know if there is a “plug-in” battery segment and a “ICE-generator” segment of the battery pack. I doubt GM will answer this question before the Volt is officially unveiled…
August 25th, 2008 at 10:51 am
30% was stated to have changed to 35% so this is probably accurate (other than the 30% part) information but old interview material.
As usual answers lead to more questions. What happens when you reach the foot of a mountain range and you battery is already depleted? No way the battery isn’t depleted to 0% on the climb, right! well maybe maybe not if you think about it. When depleting the battery even further the ICE is doing probably a good portion of the work. Still we need clarification on this issue which has come up a few times before.
Also what happens when you have the car stopped in traffic at a light and you are at 30% SOC! Surely the battery will rise above 30%. How far before the ICE turns off?
I guess we have two years to get all these answers. [shrug]
August 25th, 2008 at 10:57 am
# 60, I like the “build reserve charge switch, but why not take it a step further?
If the volt had a “smart gps” with road elevations and climb gradients in the database, it could manage the battery reserve for you. For example, say you’re headed out on a vacation from Wichita Kansas to Aspen Colorado. And you’ve punched in the destination and approved the route on your built in touch screen GPS.
1. First 40 miles out of wichita is on battery only.
2. Next 400 miles or so the battery is maintained at 30% SOC by the lightly loaded ICE, achieving the advertised 50mpg along the flat I70 (nothing else to look at here, so you might as well play with your ipodish features on the volt dash)
3. Somewhere in eastern colorado, the ICE now starts to load heavy (with a corresponding drop in fuel economy) while it brings the battery up to an 80% or better SOC by the time you get to the other side of Denver.
4. During the climb from Denver to Aspen, the ICE continues to work furiously (high loading) but is able to hold the battery to a slow bleed, (perhaps slightly limiting acceleration when you’re passing the Ford Excursion). Your battery SOC slowly depletes from 80% down to 30% by the time you reach Aspen.
It seems there would be plenty of scenarios where a gps with elevation data would be quite helpful in managing the volt’s ICE/generator/battery.
August 25th, 2008 at 10:58 am
re: #85 DonC
What you say makes sense. Could you define for the rest of us what the “number” of charges over the lifetime of a battery really means?
Does, for example, every minute charge through regenerative braking or a larger charge resulting from the ICE running have the same effect upon the battery as one that would take the 30% SOC to 80% SOC? If different, how so?
August 25th, 2008 at 11:01 am
To the best of my knowledge, this is the first time that it has been reported that the ICE will come on to run the generator vs charging the batteries. Previous articles have (perhaps erroneously as Mr Farah actually refers to in his response to Lyle’s question) stated that the purpose of the engine is to recharge the batteries, not run the generator.
More information is needed, but it appears from these comments that the main purpose (perhaps only purpose actually) of the ICE is to run the generator.
Can someone help with this question? Is the generator always directly linked to the wheels or does it only supply power once the CDP is reached?
August 25th, 2008 at 11:03 am
You guys are making this layman’s head hurt…
Its all ball bearings anyway, right?
August 25th, 2008 at 11:06 am
Take this scenario. There are three segments of the battery pack.
1. Plug-in only
2. Generator only,
3. Regenerative braking only, only releasing energy once 80% charge is reached.
This would reduce the number of charge cycles each battery cell would see. Does anyone see a problem with this scenario?
August 25th, 2008 at 11:10 am
#60 Tom,
Guess I could have read your whole post which included:
“Futuristically, the GPS could interface with the car’s computer, and do this based on destination, and known distance and elevation changes.”
Anyway, . . . yeah, what he said.
August 25th, 2008 at 11:11 am
#75 Dave G:
Actually, the “Peak Buffer” as described by Farah in the post above, can do it’s job at only 30% SOC, therefore, even if we assume that all 30% is needed for the buffer (which is actually never going to be the case since that would drastically alter the battery lifespan), then you need a battery capacity of 4.8 kw (I’m assuming the Volt has a 16kw battery and at 30% you have 4.8 kw left).
The real world battery capacity would likely be even less than that…
August 25th, 2008 at 11:18 am
I thought I understood what the typical charging sequence would be both in commuter mode and in hill climb mode, until I read the previous 89 posts…
I thought that the state of charge would be drawn down from 85% to 35% using all electric power. At 35% (and here there may be an override command to force the ICE to kick in early if you envision a hill climb) the ICE kicks in and runs at a steady rpm til the battery is at 40% (or 45%, but the chart made it look like a smaller amount). Most of the juice would go to the wheels but a lot would charge the battery. The battery reaches 40% and the car operates all electric again for 5% or about 4 miles. The charge depletes to 35%, and it starts over. The ICE will not charge to 85% unless GM allows it, but it would be an override command with limited utility since the goal is to use cheap, US produced electricity, not expensive foreign oil. Even a long hill climb can be worked around by simply allowing the driver the ability to keep state of charge a bit higher, i.e. cycling from 50% to 55% instead of the usual lower numbers. Even if I am crossing Logan Pass in Montana, I will not be ‘flooring it’ all the way, so the ICE will furnish almost all the electricity needed to drive the wheels. I think Nasaman summed it up pretty well.
Different battery types have different strengths and weaknesses, LiIon can be used thousand of cycles with little degradation if the cycles are shallow, hence the problem with the ICE charging the battery all the way up as several posters have stated.
All in all, it sounds like GM can have a great car, a game changing car, if they deliver what they are talking about, with a degree of luxury and finish at a reasonable price.
I only use 600 gallons a year as it is, so it will take a long time for $45,000 Volt to pay for itself without significant government encouragement. I am a bit of a libertarian, (small l), but the stakes are so high that I think it is worth making an exception and the government should increase the tax incentive for Volt type, EREV vehicles, to $8,000-$10,000, for the first 30,000 produced per calendar year. Then rethink, possibly increase, those numbers when Volt and IMiev production gets past that level. We need to get off foreign oil ASAP. Build wind generators, photo voltaics, nuclear power, clean up the older coal plants, get geothermal on line, build everything, but the crux of the matter is reducing our reliance on foreign oil for transport, and EREVs and BEV’s are the only way to do that.
August 25th, 2008 at 11:25 am
#45 nasaman
I’m thinking the guess of < 20 hp seems a tad optimistic. If you use 1700 Kg for mass, .5 for the CdA (optimistic?), .012 for the rolling resistance (optimistic or pessimistic?), and 1.225 Kg/m^3 for the density of air (not realistic but no way to know), at 70 mph (32m/sec) the Volt would need about 22,800 watts or about 30-31 hp to overcome aero drag and rolling resistance. (515 N from aero drag and 200 N from rolling resistance).
August 25th, 2008 at 11:34 am
I can’t believe this……
If your in a situation where you need a vehicle to climb mouantins for sustained periods, more than 1 time a year (or maybe in your life). Then you should probably buy an SUV, that way if there’s traffic you can take a shortcut through the woods.
PS
Please unsubscribe from the waiting list so i can move up. I live in the other 99% of the country where that’s not an issue.
August 25th, 2008 at 11:42 am
The question commonly being discussed here (Will the ICE charge the battery with its excess power?) doesn’t seem like the right question to be asking. Regardless of the answer, a more fundamental question exists: Will the Volt dump the generators excess power or will it adjust the generator output to match the cars needs? This is what really matters because on a long trip, regardless of whether or not the ICE charges up the battery, you’re going to reach a point where charging the battery isn’t an option….and then what? Does the Volt dump the power or does it reduce the generators output?
The answer to this question seems obvious. If the Volt can’t adjust the generators output then that’s just wasteful and poor engineering…something I can’t imagine GM would do. GM has hinted several times that the generator will have different power output levels so I believe we can assume it will. It makes no sense the other way. If the power output isn’t variable, GM would have to have the generator cranking out max hp to meet worse case scenario needs at all times, which is just silly.
If the Volt can adjust the generators output, then it only makes sense to use this all the time, rather than to use expensive gasoline to charge the battery and then switch into this more efficient mode. So we can assume the Volt will not be giving the battery a complete charge (unless if the owner was able to specify that with an ‘upcoming mountain’ mode).
The only real question that remains is what the car will do with a temporary surplus of power, but this answer also seems obvious, the car will store it so it has power available for demanding conditions. The article we’re all discussing has pretty much stated this:
“…we will take some of the energy that’s not needed to turn the wheels and bring the battery up..”
So basically, it seems very likely that the generator will have variable output levels that will not create a significant surplus of power over an extended time period. Temporary surpluses will be stored, but if those surpluses accumulate to a significant amount the car would simply run at a lower generator output level for a while to use that up. So we’d never see the battery getting much higher than a few percent above the 30% (or 35%) electric cutoff point.
August 25th, 2008 at 11:42 am
#99 JonP
Uh… no.
August 25th, 2008 at 11:44 am
56. ThombDbhomb,
58. Estero,
ThombDbhomb wrote:
“From what I’ve read, not using 1/3 of the battery is necessary for a long battery life. Using all of the battery’s stored energy would not be in your long-term best interest.”
So there are two design problems and not one
Do we know what % of the battery should remain unused to ensure long life? I don’t believe 30% has ever been stated.
The issue is that Toyota/Honda will be able to use a battery that is much smaller than the Volt’s (and therefore seriously undercut the Volt’s price) and get pretty much the same net results.
August 25th, 2008 at 11:47 am
By its design there will come a point where the battery is completely drained if I have multiple continuous grades to climb past the depletion point. Is that what I hear from this article? There is no way to charge the battery other than plug-in and braking. The ICE is just producing enough electricity to propel crusing speed and nothing more (charging battery). Sounds really wimpy to me! Is this another cop out measure by GM?
August 25th, 2008 at 11:47 am
#88 Aspherical - I missed #54 where you beat me to the point that it was the number of cycles. There will be one pack not two.
#91 Estero - a cycle starts with a 100% charge, then discharges to 0% charge, and then recharges to 100% charge. There is also a rate of charge, with 1C having the cycle occur over an hour, 2C in half an hour, .5C in two hours. The higher the C rate the fewer cycles a battery can handle. Temperature is also a factor.
By only using half the pack (depth of discharge of 50%), GM is essentially doubling the number of cycles the battery pack can handle as well as limiting the discharge rate. (As the battery pack delivers more range you don’t need to limit the DOD, which is why Tesla can get a range of over 200 miles).
Regen and charging from the gen-set count but they’re going to be minor factors. First they are are not going to change the SOC appreciably. Second the rate of charge (C rate) will be way less than 1.
August 25th, 2008 at 11:48 am
67 Estero,
I have heard the 30-80% range before, what I am wondering is why the first several dozen posters seem convinced that the generator will no longer charge the battery to 80%. I don’t see that stated anywhere.
August 25th, 2008 at 11:50 am
I didn’t read all the posts but enough to see that there are some misunderstandings about IC engines and fuel usage. Which uses more gas? An IC engine running at 2000 rpm or the same exact IC engine running at 3000 rpm? The answer is you don’t have enough info to answer the question. The IC engine will use very little power if all it is doing is idleing and turning the AC compressor. There is no “wasted” power per se that could be used to also charge the battery. Additional load in the form of generator drag would result in additional gas usage even at idle.
August 25th, 2008 at 11:57 am
To solve the “long drive followed by mount everest” problem, it might be simpler for the driver to switch to “power” mode from “econo” mode. The tesla has this option. When in econo mode, battery functions as mentioned in the article. While in performance mode, the battery pack is kept full, though not recharged from the ICE. Then it pulls power out whenever those big hills come up. This would be simpler than a GPS system.
August 25th, 2008 at 11:59 am
#100 Dan - “If the Volt can adjust the generators output, then it only makes sense to use this all the time, rather than to use expensive gasoline to charge the battery and then switch into this more efficient mode. So we can assume the Volt will not be giving the battery a complete charge … ”
The article indicates the gen-set will not be used to recharge the battery pack. So on this point we don’t have to assume anything. However I don’t see anything about several set points, only one. That may be an omission because the question wasn’t asked or it may be that they’ve changed their minds after moving to a larger engine (from 1.0 to 1.4). I’d guess the former but we’ll have to wait for something more definitive.
August 25th, 2008 at 12:00 pm
As long as we are talking about how things work lets talk about generators too. The Volts generator (all generators for that matter) only require an input load when they are generating current. If you’ve ever used a portable generator have you noticed when you hit it with a load (such as starting up a saw or some other high torque/current starting load) that the motor turning the generator suddenly changes its tune? That is because until you put the load of the saw on it the generator was just freewheeling with almost no load to the motor. Same goes for the Volt. If the batteries are already as charged as the Volt has requested there will be no load (I don’t know how they are switching) on the generator so there will be negligible load on the ICE.
August 25th, 2008 at 12:04 pm
#105 GXT - “what I am wondering is why the first several dozen posters seem convinced that the generator will no longer charge the battery to 80%. I don’t see that stated anywhere.”
I think they’re looking at statements like these. When looking at the second statement keep in mind that the Customer Depletion Point is the 30% SOC:
“People say the engine comes on to charge the battery, but that’s not what really goes on.”
“So what we’ll do then is we will opportunistically put that energy back into the battery either through regenerative braking or if we have to we will take some of the energy that’s not needed to turn the wheels and bring the battery up to the customer depletion level.”
August 25th, 2008 at 12:06 pm
customer depletion point = empty
August 25th, 2008 at 12:28 pm
Sorry, but the chaotic nature of this topic is a great example showing that educational content for Volt is needed.
It’s really hard to have constructive discussions when the basics still aren’t understood. Then there’s the reality that some fundamental questions (like engine RPM) remain a mystery.
If you want to emulate Prius, shouldn’t there be at least the same level of online resources provided? That seems to be a major gap which continues to be overlooked.
August 25th, 2008 at 12:45 pm
Sorry again if this has already been said, I haven’t read the 111 replies (boy it doesn’t take long these days for Lyle to create a new thread and for the replies/comments to fly in).
For my fellow software engineers, you should recognize the way the Volt handles series hybrid mode is very similar to network transport protocols (TCP in IP land) or queues in either a threaded program or using inter-process communication. You have a supplier (generator) and consumer (electric motor), a queue (battery), and high and low water marks that determine when the supplier comes on and off (30% being the low water mark).
I do hope the Volt allows the user (driver) to tap part of the reserve battery capacity under at least one situation…. when in series hybrid mode (ie. past the “customer depletion point”) the generator runs out of fuel (gasoline)…. so one can make a bee line to the nearest filling station. I think consumers would prefer to take the battery to 20% SoC than to wait for road side assistance (or worse a tow).
August 25th, 2008 at 12:49 pm
john1701a Says:
“If you want to emulate Prius, shouldn’t there be at least the same level of online resources provided? That seems to be a major gap which continues to be overlooked.”
The Prius is in production, the VOLT is not..
Also, I don’t think GM wants to emulate the Prius in anything besides sales!
~Bob
August 25th, 2008 at 12:57 pm
>> The Prius is in production, the VOLT is not…
That has absolutely nothing to do with discussions. And isn’t that what was meant by “game changer”, now being in a PROACTIVE mode rather than REACTIVE like in the past? It simply does not make any sense to wait.
Perhaps I should have used the word “dismissed” instead of “overlooked”, because the need for it now should be obvious. Just look at how many times the same questions get asked.
August 25th, 2008 at 1:01 pm
I have a legitimate question that I want someone to answer:
Why does everyone have an obsession with using the VOLT to carry heavy loads up steep and tall mountains?
If doing this sort of travel is daily for you, perhap it’d be a better idea to get a truck.
Bottom line: The VOLT runs pure electric for about 40 miles. After which it runs on an ICE for 300-400 miles. Any other information (and perhaps even this info.) is disputable until the release of the VOLT in 2011 (read: you’ll have to wait to find out details). Happy waiting!!
August 25th, 2008 at 1:05 pm
If this doesn’t rechrage the battery, then this car is NOT designed for long distance driving. Hybrid cars should be designed for those people who have long commutes to save on gas.
Paying mid-$30K for a car that won’t save me gas in long commutes is not a wise choice. Might as well get the Prius.
August 25th, 2008 at 1:12 pm
john1701a Says:
And isn’t that what was meant by “game changer”, now being in a PROACTIVE mode rather than REACTIVE like in the past? It simply does not make any sense to wait.
Perhaps I should have used the word dismissed instead of overlooked, because the need for it now should be obvious. Just look at how many times the same questions get asked.”
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Ahh, I see what you mean. I AGREE! Proactive information would be a boon for GM and their consumers…. but potentially their competitors as well.
Keeping that last part (competitors) in mind, it may still be a bit premature to release said information.
August 25th, 2008 at 1:15 pm
@117: You think recharging the batteries is going to save you on gas for your long commute? It’s more fuel efficient to run the motor at a lower output level (read: higher MPG) than it is to run the motor harder just so you can show up with a full charge (which you could get for pennies by plugging it at work).
To be clear, it more efficient to run the ICE at a sustainable power output, than it to to create excess power, store that power and then re-use later.
August 25th, 2008 at 1:17 pm
Albert Landicho Says:
If this doesn’t rechrage the battery, then this car is NOT designed for long distance driving. Hybrid cars should be designed for those people who have long commutes to save on gas.
Paying mid-$30K for a car that won’t save me gas in long commutes is not a wise choice. Might as well get the Prius
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The VOLT is not originally intended for really long drives. BUT, the ICE portion gets 50mpg. It will