: Chevy Volt's 'Mountain Mode' is Vastly Underrated, Yields New Driving Strategies



sgc
05-13-2011, 06:10 PM
http://www.plugincars.com/chevy-volts-mountain-mode-vastly-underrated-yields-new-driving-strategies-107176.html

Adarondax
05-13-2011, 07:01 PM
Interesting. What we really need to know is did the Volt burn less gas making those 12 Mountain Mode miles (5 more came from downhill regen for a total of 17 electric miles) than it would have used to propel the car around Seattle.

Jackson
05-13-2011, 07:45 PM
He's just addressed your question under "Comments:"


Adarondax, I guess a need a little clarification from you on your question. It didn't burn any gas making those 17 electric miles. They existed because I charged it from the grid (and some of them were regenerated as I was going downhill using energy that would normally be wasted in braking). Emissions associated with the electricity used to charge the batteries vary widely by region, but are generally much less per mile than burning fuel. Cost per mile using electricity will also vary widely by region depending on how much you pay per kWh, but are also generally much less than the cost per mile of fuel even at 43 mpg (something like 2-3 times less expensive). Where I live, 96% of my energy comes from dams (no emissions) and it is the cheapest in the country at 3 cents per kWh, so it's always better to drive on electricity here.

All;

The phrase "Mountain Mode" was first coined on this site when the Volt was still in development. We often discussed what we called "The Pike's Peak Problem," describing a theoretical situation in which extra power might be needed to get up a long grade. This feature was envisioned as a battery reserve of maybe 10 miles, to provide that extra "oomph" when required. When this actually showed up on screens in production-ready prototypes, it was assumed that the mode had been lifted directly from our discussions; but apparently not: The description in the article seems to be much more like the "Hold" feature which was also discussed (We considered a feature which would simply force the Volt into Charge Sustaining Mode). Not that the actual "Mountain mode" is completely like our "Hold" idea; the truth seems to be somewhere in the middle: a more subtle blending of the two. This has produced a mode preserving the benefits of both; showing a great deal of thought and research on the part of GM's Voltec engineers, IMO.

DonC
05-13-2011, 08:55 PM
Interesting and illuminating. I'll give him props for this one.

Adarondax
05-13-2011, 10:13 PM
I believe Mountain Mode builds a charge in the battery by running the engine, sometimes at high revs. This is how it's described on page 9-27 of the Volt Owners Manual:

"Press the DRIVE MODE button to select Mountain Mode. If steep hill driving is expected, it is recommended to select Mountain Mode at least 20 minutes before driving on steep grades. This will allow the vehicle time to build a sufficient battery charge reserve. The engine may run when Mountain Mode is selected. If Mountain Mode is entered before four bars of battery charge, the engine will
run at a higher speed to build battery charge reserve. If Mountain Mode is entered above four bars of battery charge reserve, the
estimated electric range will adjust accordingly."

That means that Mountain Mode isn't just maintaining the battery's state-of-charge, it is burning more gasoline to add to the charge. That is the basis for my question.

petefoss
05-14-2011, 08:32 AM
Depends on when you switch modes. If the battery is above the minimum state of charge for Mountain mode when you switch, it will switch to CS mode when you get there and maintain that level. If you are below the minimum state of charge for Mountain mode when you switch, it will drive the engine harder to drive the vehicle and charge the battery up to the minimum.

Pete Foss GM R&D

DonC
05-14-2011, 10:30 AM
@petefoss

Do you think he's right? Obviously you want to use the battery as much as possible, but if the trip distance will exhaust the battery it makes sense to me to use the most efficient mode for the drive cycle. IOW best to use the battery in the city and the genset on the freeway. I also think that by setting Mode Mode before embarking on the the trip he avoids having the engine rev to charge the battery up to whatever the Mountain Mode depletion point is. Interested to hear your take on this.

Jackson
05-14-2011, 11:22 AM
If you're concerned about burning gas, select "Mountain Mode" well before the usable pack charge is exhausted. Problem solved.

Luvthevolt
05-14-2011, 11:35 AM
Might be the way to go. On the Highway switch to Mountain Mode and when your about to get off go back to normal, but only for long distance.

ClovisVOLT
05-14-2011, 01:56 PM
Yes, the Mountain Mode has some pretty nice features and may actually help with hypermiling.

I commute about 180 miles each way and then live a couple miles from the office during the week at a corp apt. I start the trip by running the volt in EV about 25 miles under 60 mph (light city and single lane highway) and then switch to Mountain Mode when reaching the 6 lane freeway.....this slower route is the most EV efficient and just as fast with fewer miles.

After about a hundred miles in CS mode (with MM on) when I get within a dozen miles or so of the office and put it in Normal mode and burn no gas in either city location. This maximizes the EV miles to between 40-50 every time and allows CS at > 75 mph (which would deplete the batteries really fast).

This also allows me to take the one mountain between locations on in style - push into Sport mode and blow past everyone else on the road (ok, not efficient, but fun from time to time).

I always arrive at both locations (home and office) with close to or at zero EV miles left.

Apparently, the Euro models will have a full switch between modes so you can retain all your battery to arrive at the city center w/o having to worry about emmissions....the wave of the future. GO GM, GO VOLT, GO SOLAR, GO MM

adamsocb
05-14-2011, 02:05 PM
The highway/city case is a great example. I also use the mountain mode when I want to arrive at my destination with enough charge to give demonstration rides/drives. I have done this several times when traveling to friends or relatives homes and when attending eco-related events that are more than 20 mines from a full charge. I just set to Mountain Mode when I leave and then back to Normal when I get to my destination. There is usually about 16 miles of battery electric range available when I switch back to normal.

larry4pyro
05-14-2011, 03:05 PM
I have to drive up to Los Angeles from the San Diego area ocassionally. By going into Mountain Mode I can reserve about 14 miles or so of battery charge for city driving. In order to drive on the battery I have to switch back to Normal Mode when I get into the city.

I've also noticed that if you activate Mountain Mode after the battery has been depleated the ICE runs harder and there is a noticable decrease in performance. This is expected since it is now recharging the battery to the higher Mountain Mode depleation point. But what I didn't expect was the ICE stayed on at quite a high RPM when the Volt was stopped at a light. Of course running the ICE at high RPMs while stopped really hurts my gas mileage. So I think if you are going to use Mountain Mode to recharge your battery for some additional battery range you probably should do so while moving.

I also noticed that running in Mountain Mode after depleating the battery than switching back to Normal Mode results in false readings in electric mileage. After playing around with the two modes the display showed an electric trip range of almost 60 miles, but I know I only went 47 before the ICE initially kicked-in.

sparks
05-14-2011, 03:17 PM
Good topic! I've been onto this for awhile. Yes, I have found that MM can be used to reduce the overall amount of gasoline burned if your commute is mostly freeway, with in-town driving at either end. I commute about 50 to 55 miles (round trip, plus lunch) per day, so I am forced to do about 14 miles per day on gasoline. (Granted, that's not much gasoline no matter how you slice it.) Anyway, while nearing the end of the freeway portion on the way home, I turn on MM about 4 miles prior to hitting the in-town leg. The ICE is already running, so basically I just load it down all the more, by forcing it to charge the battery at the same time it's maintaining about 70 MPH on the freeway. The rationale is that, once an ICE is running, it's inefficient anyway, but the more you load it down, the more efficient it becomes. When I get into town, I switch into Sport and go the rest of the way home on the battery (the ICE comes on in the final block sometimes). Overall savings: About 0.1 gallons (end up using .30 instead of about .40).

I should mention, the only reservation I would have about this, is if MM causes the ICE to NOT clutch into the wheels at highway speed. Recall, GM engineers allow the ICE to help drive the wheels (once it is in CS mode), especially at highway speeds, because it adds about 10% to the fuel economy. If MM forces the ICE into an RPM range that is not usable for clutching into the wheels, then we might pay an efficiency penalty there (although it may be compensated by the greater ICE efficiency under load -- this is getting complicated!). Anyway, the proof is in the pudding, and it looks like I am seeing an overall efficiency gain using the strategy described above.

Rusty
05-14-2011, 05:25 PM
I should mention, the only reservation I would have about this, is if MM causes the ICE to NOT clutch into the wheels at highway speed.

I don't believe it does (although somebody who really knows would need to chime in). If the ICE is running higher RPMs, it just means the traction motor needs to run at lower RPMs to drive the CVT. I'd think that might be less efficient than non-MM, but once you're in MM you're less about efficiency anyway.

I believe the ICE *does* declutch regardless of speed if you enter reduced power mode. Once in RPM the ICE spools WAY up. When I tried it, it felt like the tranny went into neutral until the speed dropped below 70. But I wasn't there very long before I hit in the 60s, so I'm not sure.

wainair
05-14-2011, 07:25 PM
Good reading for sure. I once posted a call for hold mode but the more I read here the more I think MM might be better!:)

Rusty
05-14-2011, 07:59 PM
I once posted a call for hold mode but the more I read here the more I think MM might be better!:)

No, I don't think so. MM is really good for what it's intended (and doing demos). But I think the ICE runs less efficiently than Hold Mode would do. I'd really like HM so I could run at whatever SOC I engage it, with the ICE running identically to how it runs in CS mode.

There's no real reason we can't have both MM and HM. It's just software!

Luvthevolt
05-14-2011, 09:03 PM
I second having the hold mode as well.

marlow
05-14-2011, 10:13 PM
Mountain mode is great for demos, with less than half of a charge on the battery you can control weather you are running on battery or the ICE and show how the bayyery can be recharged some by the ICE (with some performance loss) the efficiency loss was not as bad as I expected, with a drop from about 40 MPG to 20 MPG about 2/3 of a mile of battery capacity recovered for every mile driven.

gwmort
05-14-2011, 11:26 PM
I did a test on a long highway trip, when I had about 3 miles of AER left I switched it to MM, it revved high and after 6 miles I had burned about 1/4 of a gallon (24mpg),so I switched back to normal and now had 9 miles of AER showing, six miles later I was able to repeat the test (level highway cruise control set to 64mph). I stopped doing it because I feared I was forcing additional cycles that would shorten battery life. However if it isn't damaging to run that way (and you aren't too annoyed by the high revs) combining the 24 mpg, plus 6 bonus EV miles every 1/4 gallon is around 48 mpg. Sort of a super-pulse-and-glide.

ClovisVOLT
05-14-2011, 11:37 PM
I did a test on a long highway trip, when I had about 3 miles of AER left I switched it to MM, it revved high and after 6 miles I had burned about 1/4 of a gallon (24mpg),so I switched back to normal and now had 9 miles of AER showing, six miles later I was able to repeat the test (level highway cruise control set to 64mph). I stopped doing it because I feared I was forcing additional cycles that would shorten battery life. However if it isn't damaging to run that way (and you aren't too annoyed by the high revs) combining the 24 mpg, plus 6 bonus EV miles every 1/4 gallon is around 48 mpg. Sort of a super-pulse-and-glide.

Good test - if not too much to ask, next time you're into doing a test can you do the same at 75MPH? I've found the extra EV miles generated do not translate into actual miles if you're much over 60MPH, which drives down the overall mpg....which is why I MM whenever over 70MPH and then Normal when under 60 or so.....seems to work well, but haven't run the numbers yet - it's tough since prevaling wind speed also will impact mpg by upto 5mpg at 70+mph. GO VOLT, GO GM, GO MM - WE NEED A HOLD MODE!

Rusty
05-14-2011, 11:58 PM
WE NEED A HOLD MODE!

Sounds like we also need a PaG Mode (Pulse and Glide). One of the things GM needs to improve (if they can) is the long haul MPG. And it sounds, based on gwmort's test, that they can... I don't want to switch in and out manually, I want the car to do whatever it needs to do to use the least gas while on the long.

wainair
05-15-2011, 12:26 AM
Ultimately both would be even better. MM and Hold mode. Like you say Rusty, it is just a software patch. Though I'm still impressed with MM as portrayed in this article. It has more usefulness than I had given it credit for.

Luvthevolt
05-15-2011, 12:30 AM
Sounds like we also need a PaG Mode (Pulse and Glide). One of the things GM needs to improve (if they can) is the long haul MPG. And it sounds, based on gwmort's test, that they can... I don't want to switch in and out manually, I want the car to do whatever it needs to do to use the least gas while on the long.

Do you think GM has a reason for not having it set up automatically to use the least gas? I wondered that myself.

marlow
05-15-2011, 08:11 AM
The energy conversion efficency of the regen and using the ICE in Mountian Mode seems to be almost 70%, which is better than the 50% I expected, as it takes energy to convert energy motion or gas to electricty and to store that energy and then use it to make motion.

As an example, if I am driving in Normal CS (Charge Sustaining depleted battery) mode getting 40 MPG then switch to Mountian Mode for a few miles will lower my MPG for thoes miles to about 20. However the battery will have gained energy that when the mode is switched back to normal and when used, will pick the average MPG (for the Mountian mode miles and the following Normal Mode miles on battery) back up to almost 37 MPG, that is much better than the average 30 MPG that I expected.

Luvthevolt
05-15-2011, 09:21 AM
Would it be a good idea that if say you have a 200 mile trip to switch into mountain mode when on the highway and when your about to get off switch back to normal?

wainair
05-15-2011, 10:41 AM
Yes it would be a good idea. Highway driving uses up the battery very fast and MM would put it in CS mode early, saving extra charge that wouldn't be saved if you let it go into CS mode on it's own. Then the extra saved battery power can be used when you are off the highway were the battery power is much more efficient.

scottf200
05-15-2011, 11:29 AM
<SNIP>Anyway, while nearing the end of the freeway portion on the way home, I turn on MM about 4 miles prior to hitting the in-town leg.<SNIP>

Mtn Mode(MM) does not know how far you are from the mtn so it is pretty aggressive RPM and higher (and the reason it runs even while stopped). I experience/discussed MM with an engineer on the unplugged tour where she talked about the aggressive RPM.

The State Of Charge(SOC) it wants is 13ish miles (4 bars per article) so it would seem you should turn on MM sooner than 4 miles so you don't get the aggressive RPM but modest ones. Food for thought.

Note from the article he switched over before the MM SOC:
At that point I switched to Mountain Mode and within three miles my Volt test car switched over to charge-sustaining hybrid mode.

From a comment [Adarondax] on the article that quotes the Volt's manual :

I believe Mountain Mode builds a charge in the battery by running the engine, sometimes at high revs. This is how it's described on page 9-27 of the Volt Owners Manual:


"Press the DRIVE MODE button to select Mountain Mode. If steep hill driving is expected, it is recommended to select Mountain Mode at least 20 minutes before driving on steep grades. This will allow the vehicle time to build a sufficient battery charge reserve. The engine may run when Mountain Mode is selected. If Mountain Mode is entered before four bars of battery charge, the engine will run at a higher speed to build battery charge reserve. If Mountain Mode is entered above four bars of battery charge reserve, the estimated electric range will adjust accordingly."

That means that Mountain Mode isn't just maintaining the battery's state-of-charge, it is burning more gasoline to add to the charge. That is the basis for my question.

marlow
05-15-2011, 07:13 PM
After purchasing my Volt in New York and driving it to Michigan I swiched to Mountian Mode as there were some big hills to go through.

I did not think of it at the time, but when I was stuck in construction traffic with the air on, it most likely would have been better to switch back to normal mode and run on battery.

PatsVolt
05-15-2011, 08:49 PM
After seeing the talk about mountain mode, I decided to experiment with MM. We were on an errand that would take the range to the limit. So I decided that when the battery reached 18 to 20 miles remaining I would put MM on. I did so with the following results.

Battery indicator switched to 2 miles to go. I drove the 2 miles and the ICE started, but at very low revs.

I had my trip meter set to record CS miles the other day, so I did not reset it as it would have gone to 250+ mpg.

I had 93 miles traveled and the MPG was 58 MPG.

I drove the next 18 miles on MM.

The MPG remained between 57 and 58 MPG for those 18 miles.

The ICE would run occasionaly and would turn off for long periods of time, but would always show CS mode.

Average speed was 30 MPH 20 to 45 MPH range. The route was mostly back roads and rolling terain.

What struck me was that the MPG never dipped below 57 MPG.

When I arrived home I still had 16 miles remaining in the battery and only two miles was used off the battery.

Pat

volt11
05-15-2011, 10:44 PM
Sounds like we also need a PaG Mode (Pulse and Glide). One of the things GM needs to improve (if they can) is the long haul MPG. And it sounds, based on gwmort's test, that they can... I don't want to switch in and out manually, I want the car to do whatever it needs to do to use the least gas while on the long.

For God sakes please don't add "pulse and glide". If there's one thing I can't stand, it's being stuck behind some moron who speeds up and slows down. And if there's another thing I REALLY can't stand, it's being a passenger in the car of the "pulse and glide" driver.

volt11
05-15-2011, 11:03 PM
I think I disagree with some of the MM techniques being used in the quest to get more efficiency. IMO, whenever the engine is being used to actually build up a charge rather than sustaining one, you're losing efficiency. However, I do use MM to improve efficiency on my commute, and how I use it is based on my observation that when the engine first kicks into CS, if you're just doing stop and go in what's essentially city driving, the mileage is relatively terrible for the first several miles (as I presume the engine warms up), like under 25mpg based on mental arithmetic watching the efficiency display. If you're on the highway during that cold engine start, I find that you get a lot more distance for that first quarter gallon or so, like over 30mpg, and of course it climbs from there.

So on the principles that we want to minimize the number of cold starts, and that it's better to cold start at highway speeds than at local speeds, I use MM accordingly. My typical day is ~42 miles to work. Then I'll do about 5-6 miles to go out to get lunch. Then the 42 mile trip to return home. If I do nothing with MM, that will often mean going into CS mode before reaching work, meaning almost all cold operation for that leg for a very short distance, then another cold start to go to lunch at local speeds, and then another to head home, again where engine warm up occurs at local speeds (since work is about 12 miles from the major highway.) So instead of 3 worst case CS mode engagements, by using MM on the way to work I have the engine kick in while still running somewhere between 50 and 70 MPH (about 2/3 of the way there). Then I go to lunch on all electric, with still some electricity left to get me about halfway to the highway on the way home, and usually by that time I'm on a 50mph road. The MM strategy therefore means only 2 cold starts, and under the more efficient highway conditions. Plus if I have someone go with me to lunch, they get to experience the Volt on pure electricity. In the end, I believe my 90 mile day's MPG improves by 5-10MPG by simply setting MM on the way to work.

Rusty
05-15-2011, 11:23 PM
For God sakes please don't add "pulse and glide". If there's one thing I can't stand, it's being stuck behind some moron who speeds up and slows down. And if there's another thing I REALLY can't stand, it's being a passenger in the car of the "pulse and glide" driver.

I think you've misunderstood what we're talking about here for a Volt PaG mode. The engine pulses (runs longer and harder then CS mode normally would) and glides (engine doesn't run at all, car runs in CD mode), but the car's speed stays the same (doesn't need to actually, but if you're on the highway it could). Engine speed and vehicle speed have very little to do with each other with the Volt.

volt11
05-16-2011, 12:09 AM
I think you've misunderstood what we're talking about here for a Volt PaG mode. The engine pulses (runs longer and harder then CS mode normally would) and glides (engine doesn't run at all, car runs in CD mode), but the car's speed stays the same (doesn't need to actually, but if you're on the highway it could). Engine speed and vehicle speed have very little to do with each other with the Volt.

Ah, sorry, my misunderstanding. But isn't that a Prius hypermiling technique, to do surges of power followed by coasting?

As to this definition of pulse and glide you clarified, I'd be surprised if it yields improved efficiency, unless there's a sweet spot for engine power (and possibly generator efficiency) vs. gas used that's higher than normal CS operation under typical conditions. It would have to be so much better that it could overcome the inefficiencies of storing the excess power in the battery.

Of course even if that's the case, it would be a lot more annoying to most drivers, unless Chevy could get the engine so smooth and quiet under those conditions it would be not very noticeable. Where as we know in the current Volt, when the engine revs there's no mistaking its presence in both noise and vibration. It's still very acceptable overall, but if they made the Converj or any Cadillac version of Voltec (which I really hope they do), they'd really have to improve that area to suit the Cadillac brand.

Rusty
05-16-2011, 12:51 AM
Ah, sorry, my misunderstanding. But isn't that a Prius hypermiling technique, to do surges of power followed by coasting?

Yup, and I hate it when they do that!


I'd be surprised if it yields improved efficiencyI would be too, but we've had one report that it does. I'm not in good terrain to try to verify the test (too many hills, and I haven't burned gas a several weeks anyway). I'm hoping somebody else gets the bug and tries it out.


Of course even if that's the case, it would be a lot more annoying to most drivers, unless Chevy could get the engine so smooth and quiet under those conditions it would be not very noticeable.Yep, it'd be *really* annoying to the hoi polloi. MM is very noticeable, so PaGM would have a big impact on NVH. But if it works, that's why it should be an optional mode. If I really want to run in a presumably working PaGM, having the car transition between MM and CD would be a *LOT* less annoying to me than making me do it manually. Safer too, as it'd be a driver distraction.

George S. Bower
05-16-2011, 01:18 PM
Fascinating thread. Way to go gwmort for your discovery of the pulse and glide technique (yes it's not the same as pulse and glide in the Prius) This all gets back to a discussion we were having a while back about engine off time. I believe pulse and glide as gwmort was describing would work best on long flat stretches of freeway where there is little chance for regen. The theory is that you run the engine at a higher load point w/ better sfc for a short period of time, then turn it off totally for as long as possible, so you've accomplished 2 things: 1) you have run the engine for a shorter time at a higher load condition and a better sfc and 2) you are maximizing engine off time and engine off time is king.

I still think we need the MDI to dig deeper into how the Volt works and am hoping since I don't have a Volt yet one of you guys that do will get the ball rolling when the system is available.

I would like to see, at a minimum, a light that went on when the mechanical link clutch is engaged (separate subject).

Rusty
05-25-2011, 01:31 AM
Well Holy Moly, that works!

Drove up to the USC Medical Center today (243.1 mile round trip), and tried the P&G technique on the way. Speeds for the most part were 70-75 MPH, short the requisite LA rush hour stop and go on the way home (way up was clear running). I only pulsed when speeds were greater than 50 MPH, otherwise operating in normal. The first 33 miles were "free". Temperature was "we're in So Cal, in May, shuddup." Tire pressure at 36 PSI cold. Results? Car reports:

74.2 Electric Miles, 168.9* Gas miles, 5.12 Gallons burned, Trip overall 47.5 MPG. If I take out the free miles that's 41 MPG @ 70+ MPH.

I'd expect to see 34-35 MPG at those speeds, so that represents about a 20% improvement in measured MPG!

Key points for the test was to not pulse (aka MM) below 50 MPH. I think MM at idle just wastes gas, but the incremental RPMs at speed apparently improve the SFC significantly. Coincidentally that means there's a negligible (really negligible) affect on NVH. While I normally find MM annoying, it didn't bother me in the least at speed.

The Prius moments? Based on EPA I normally say the Prius moment (where the Volt crosses over 50 MPG, starting with a full charge) is around 120 miles. Using P&G I didn't drop to 50 MPG until 149.3 miles, during a pulse. During the next glide I got BACK to the Prius moment at 180.6 miles. And that was the end of the glide, I slipped under the Prius moment for the last time at 181.8 miles.

Really, 181 miles before final crossover? Does a Prius get 50 MPG at 70-75 MPH?

*On the way up, when I transitioned from MM to NM the gauge switched from gas to battery. On the way home (doing the same thing) the gauge always stayed on gas. I've complained about that before. So all the 10-15 mile glides on the way home got added to the gas range.

Paul Slazas
05-25-2011, 09:23 AM
http://www.plugincars.com/chevy-volts-mountain-mode-vastly-underrated-yields-new-driving-strategies-107176.html

Thanks for the article. I am going to try Mountain Mode on my 37 mile drive to work tomorrow! Paul S. Red Volt# 2169

dtaubert
05-25-2011, 01:19 PM
Awesome thread! The general idea here is to use MM on the highway in CD mode to build up just enough charge to cover in-town driving? For example, before a pit stop on a long trip?

Slapshot28
05-25-2011, 04:20 PM
Awesome thread! The general idea here is to use MM on the highway in CD mode to build up just enough charge to cover in-town driving? For example, before a pit stop on a long trip?

I this is a great strategy, and one that I have used quite a bit. Here are some thoughts:

- The primary goal always should be to arrive home "on empty" in terms of SOC.
- MM is much faster at charging than plugging in: 20-30 minutes recoups quite a few miles of battery.
- Better still, start MM before you get below 15 miles of range so that MM just "tops off" the battery.

I try to use MM sparingly, only when I'm certain that I will need the extra battery range. It's no big deal to drive the last few miles home burning a bit of gasoline. And I kind feel like a dope if I was clever with MM, only to arrive home with a bunch miles left in the battery. Doh!

JohnK
05-25-2011, 04:54 PM
Have not read the start of this thread yet, but will contribute my little experience. I had the Volt for about 3 weeks and took it for a trip to Ohio (about 400 miles round trip). Left at end of a work day, so the battery was already discharged. Had been using the ICE for portions of commute (did not yet have plug-in permission), so I filled up the gas tank before the trip. When I got near my home town, I put it into MM so I could demonstrate electric driving. Oddly, nobody was excited enough to want a demo. So started back home with a little bit of electric charge - but it came from gasoline. When I got home, the MPG was 45.4! Did 30 miles of MM help to raise the MPG? Don't know, but it did not seem to hurt.

larry4pyro
05-26-2011, 02:08 AM
Assuming the battery is depleated and you select Mountain Mode. How many kilowatts are pumped into the battery? Say it takes 10 minutes. If it takes 4 hours to fully charge on 240 VAC and that buys you about 40 miles, then the charge rate is about 10 miles per hour of charge. If I get 14 miles of charge in 10 minutes in Mountain Mode than the equivalent charge rate must be 84 miles in one hour. That would inply that the power sent to the battery in Mountain Mode must be like 8.4 times greater the power delivered by a 240 volt charger!

So, what do you think? Potentially dangerous for the battery? Or no problem, particularly as regen braking probably generates a lot more power. I don't know, but it's just another thing to consider when using Mountain Mode.

Rusty
05-26-2011, 02:37 AM
Assuming the battery is depleated and you select Mountain Mode. How many kilowatts are pumped into the battery? Say it takes 10 minutes.

It doesn't. It seems to take about 20, depending on driving conditions. It charges to 4 bars, so if the useful capacity of the battery is 10.5 kWh that's 4.2 kWh in 1/3rd of an hour. Or 12.6 kW. You also get 10-13 miles range out of the deal (depending on how you drive), so call that 35 MPH charging, or 3.5 times faster than a 240V EVSE.


So, what do you think? Potentially dangerous for the battery? Or no problem, particularly as regen braking probably generates a lot more power.Regen generates up to 60 kW. Battery charging is rated in C (capacity) in time. So charging the Volt's battery at 16 kW would be a 1C charge rate. The full regen 3.75C is a bit much to want to do all the time. MM's .8C (ish) charge rate isn't a problem. Charging a Li-Ion at 1C (or even 2C) is well within the batteries capabilities. Even if it were twice that at 1.6C it wouldn't pose much of a problem, especially with the Volt's TMS. Thinking about it, and remembering charge efficiencies, probably bump the numbers by 25% for an 80% charge efficiency, but that makes it nearly exactly 1C, which is fine.

Good question though!

kmg
05-26-2011, 04:00 PM
This thread and another one about MM has been very helpful in changing my strategy for planning trips involving lots of freeway driving. I don't mind running the engine on the freeway, as long as it is not running at high RPM, because you mostly can't hear it, like you can at slower speeds on city streets.

A few days ago I needed to take some folks to the airport, about 100 miles roundtrip. I left the house in M mode and with a full charge. On mostly freeway driving, M mode allowed me to drive 25 miles on battery power, depleting the battery down to 4 bars, then it switched to CS mode. Upon exiting the freeway, I switched to Normal mode for city street driving in the vicinity of the airport. Nice, quiet, stop and go battery only driving. The range showed 15 miles battery power. Later, upon reentering the freeway, I still had 4 bars showing on the battery, and switched back to MM. When I was about 20 miles from my house, I switched to Normal mode, and got to within 1 mile of the house before the engine came on.

That was 44 miles under battery power, and I did not hear or feel the engine running anywhere until I was on my
street and approaching the garage. Love it.

Ken. #1228

Steverino
05-26-2011, 09:20 PM
I used the same strategy driving back from NY to IL. I used Mountain for highway driving to preserve 4 bars for city/stop&go traffic. It does not seem to matter if you wait until the battery is at 4 bars before switching to Mountain as it does not charge until then anyway.

It would be nice to have a way to preserve more/most of the battery for city driving at the beginning and end of a long highway trip. Sounds like that's what the Ampera will have.

Rusty
05-26-2011, 09:31 PM
It would be nice to have a way to preserve more/most of the battery for city driving at the beginning and end of a long highway trip. Sounds like that's what the Ampera will have.

Yup. "Hold Mode". Europe gets it. We (and GM) don't get it. Many of us (but apparently not GM) want it.

Jeff N
05-27-2011, 03:58 AM
Yup. "Hold Mode". Europe gets it. We (and GM) don't get it. Many of us (but apparently not GM) want it.

This is entirely a governmental regulatory issue with the EPA. The Volt (Ampera) will have an "EV hold" button when sold in Europe and I think it is very likely that the Volt built for and sold in the U.S. is capable of this also but just needs the button to be installed and wired up correctly. I doubt it will take too much longer before someone reverse engineers this. Similar story with the 2nd generation Prius "EV" button and the 1st generation Prius cruise control. The computer hardware and firmware is all essentially the same between models sold in different countries and we just have to tap into the right place in a wiring harness.

Does anyone know how the hold mode is enabled in the Ampera? What is the user interface?

Rusty
05-27-2011, 04:44 AM
Does anyone know how the hold mode is enabled in the Ampera? What is the user interface?

I was originally thinking "duh, software mod. Goes with normal/sport/mountain. Just add one." No button changes, just a software change. Then a comment earlier today reminded me it might be better to be a separate button.

Else if bundled into all the other modes, you'd want a "Hold Mode" and a "Sport Hold Mode". And that would make five. No need for a "Mountain Sport Hold Mode", 'cause that'd just be silly!

Jeff N
05-27-2011, 11:51 AM
http://media.gm.com/content/autoshows/Geneva/2011/public/gb/en/vauxhall/news.detail.html/content/Pages/news/gb/en/2011/Geneva/Vauxhall/02_23_ampera_geneva

Unfortunately, at this page GM describes it as just another mode controlled by the Drive Mode button like Mountain Mode and Sport Mode. No mechanical buttons and wires that we can trivially tap into. I suppose there could be some kind of physical wiring that the computer tests to select region-specific behavior but it's at least as likely that they just create slightly different regional versions of the firmware.

I think Toyota was eventually permitted to include the EV button on the factory-built U.S. version of the Prius so GM might eventually add Hold mode for us as well someday. Mountain Mode may just be a "foot in the door" as the discussion continues with the EPA. We can all complain to Congress about this also.

voltcrazy
05-27-2011, 01:06 PM
What a great article and thread. I have a 150-mile drive every other week from Santa Clara to Manteca, CA and back I was getting 48 MPG on this drive before reading this thread, as well as the thread on hypermiling (http://gm-volt.com/forum/showthread.php?7768-Hypermiling-your-Volt&highlight=hypermiling). The results are amazing. I am now getting 58 MPG on the same exact drive, in about the same temperature range (high 60's to low 70's).

What I am doing differently, exactly? First, I turn on MM as soon as I leave the house, and switch back to Normal mode when I get close to Manteca. This way, all of my "city" driving is on electric, and I run the ICE on the freeway where it is more efficient.

Other changes:
1) 60-65 MPH instead of 70 MPH
2) Tire Pressure at 40 PSI instead of 35 PSI (going to try 45 PSI next)
3) Paying attention to momentum and conserving it when approaching stoplights, as well as stop and go traffic, etc.....more details in the hypermiling (http://gm-volt.com/forum/showthread.php?7768-Hypermiling-your-Volt&highlight=hypermiling) thread

larry4pyro
05-27-2011, 03:07 PM
Never used the Hold mode so I don't know for sure. In Mountain Mode you can elect to charge the battery state of charge by engaging Mountain Mode after the battery is depleated. In Hold Mode you can select when to use the ICE, but I haven't read anything about the ICE charging the battery in this mode. I assume it does just what the name implies, Hold battery SOC at whatever level it was when the Hold Mode was engaged. But if the battery is depleated when Hold Mode is engaged, I haven't read of anything saying the ICE will raise the SOC.

N4CVX
06-08-2011, 04:56 PM
Fascinating thread! But this Newbie guy is going to ask a really simple (maybe dumb) question: "Why not just leave the settings alone and drive the car?" I realize this may be an oversimplification, but I am also thinking that you are talking about "hypermiling" the car as opposed to just driving it the way it was designed to drive. In my case, I have a 25 mile round trip commute with weekend trips of about the same number of miles. I apologize for asking what may seem to be an incrediably elementary question to you experienced folks out there.

Rusty
06-08-2011, 06:39 PM
Why not just leave the settings alone and drive the car?

You can do that. It's a perfectly fine car, well refined, easy to drive. On the open road it behaves as you would generally expect a car to behave (with a few quirks).

And that's the way most people will probably drive it. I think GM's goal was to make the Volt driving experience very much like any other regular car, just without the whole annoying (and expensive) gas thing (and with the fun extra torque thing :-).

What we're gaming here is "how do we make the Volt *not* drive like just any other car?" How can we take advantage of some of the special things the car can do.