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Discussion Starter · #1 ·
I was just talking to someone who is driving one of the test a plug-in Priuses. He has had it about a week. Apparently he was adivsed that if the temperature was below zero not to charge the battery and if the temp was -20F do not drive the vehicle at all. Why? Is this bad for the battery or the car? Being in Maine we can get temps well below zero in the winter. With the thermal management system in the Volt, is this a concern? I was surprised to hear this.
 

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They held up release of the 2011 models last November to do last minute testing in Fairbanks, AK. I don't recall they had any issues with the extreme low temps. The Volt also turns on the ICE when temps go below 26deg F to provide heating.
 

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The more I read about charging issues other cars have that are related to battery longevity, crippled winter range, lack of thermal management, etc., the more brilliant the Volt's engineering looks.
 
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@ VoltinME,

This actually came from a previous post:

If the Battery Too Cold, Plug In to Warm message is displayed on the Driver Information Center of the 2011 Volt, the vehicle will not start until the high voltage battery is warmed up. This condition usually occurs on vehicles that have been parked for a prolonged period of time in extremely cold temperatures (approximately -14°F or -25°C) When the vehicle is subjected to cold temperatures for an extended length of time, the electrolyte in the high voltage battery cells starts to freeze. Once this occurs, current cannot pass through the battery for any reason, such as starting the gasoline engine or powering the battery internal heater. It is a physical limitation much the same as diesel fuel gelling at very cold temperatures and making the vehicle impossible to start. If this condition occurs, plug in the vehicle to allow the charging system to warm the high voltage battery, and then the vehicle can be started. Without a charger to provide power from somewhere besides the high voltage battery, the contactors cannot be closed and the vehicle cannot be started. The Volt does not have a conventional 12V starter and needs the high voltage battery to supply voltage to the electric motor to start the gasoline engine.

The best tip for when you live in area that can get that cold, keep the Volt plugged in when possible, even when fully charged, to keep the battery temperature ready for the next drive.
 

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Trevor is the same true of extended periods at high temp (100F+), will the battery temp management eventually run the battery into a discharge state.
 

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It seems that everytime this question is asked, the general consensus is that if the Volt is going to be stationary near an outlet for an extended amount of time, there is benefit in plugging it in regardless of the battery SOC.
 

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The more I read about charging issues other cars have that are related to battery longevity, crippled winter range, lack of thermal management, etc., the more brilliant the Volt's engineering looks.
Totally agree. I am pretty confident that the Volt is the best EV in cold Ottawa winters. The fact it also has a dual heating is cool too (i.e., can heat cabin on electricity only but is also smart enough to redirect heat from generator to cabin when running in CS mode). Trust me you have (and I will have soon!) the most advanced vehicle on the planet!
 

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@ VoltinME,

This actually came from a previous post:

If the Battery Too Cold, Plug In to Warm message is displayed on the Driver Information Center of the 2011 Volt, the vehicle will not start until the high voltage battery is warmed up. This condition usually occurs on vehicles that have been parked for a prolonged period of time in extremely cold temperatures (approximately -14°F or -25°C)
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The only question that leaves is exactly what is "a prolonged period of time"? That is kind of vague.....

If I go to work at 7:30 AM and it is below zero outside, and maybe have to work late until 6:30 PM, is 11 hours considered "prolonged"?

Or are we talking about days or weeks? That term can mean different things to different people.

And I don't have a way to plug in at work, so this could be important!

Thanks.
 

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The only question that leaves is exactly what is "an prolonged period of time"? That is kind of vague.....

If I go to work at 7:30 AM and it is below zero outside, and maybe have to work late until 6:30 PM, is 11 hours considered "extended"?

Or are we talking about days or weeks? That term can mean different things to different people.

And I don't have a way to plug in at work, so this could be important!

Thanks.
I think this depends a little bit on how cold it is outside. The Volt's battery is well insulatd, and will stay warm for many hours, if not days, under almost all reasonable circumstances, even in Canada! If it's -50 F, then heat will transfer out of the battery pack faster. Then those "many hours, if not days" could turn into just a few hours. That's because conductive heat transfer rate is proportional to temperature difference. (q = U * A * deltaT) Make sense?

If you are only worried about a normal workday, you should be fine. I can't imagine the battery losing that much heat that quickly. Plus, if you get really worried, just remote start your Volt at lunch time, to warm it up.

P.S. Try to keep your Volt away from wind if the temperature is really really cold, because wind will add a small bit of convective heat transfer.
 

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So we need a phone app for the battery temperature, the sensor is there so i would guess the car should warm up the pack every few hours or so. I'm willing to give up reserve power in the pack during cold winter to keep the pack from reaching those low temps. Mighty cold here in Quebec and i'm not very fond of getting in the car and having to wait 10 or 15 min. for the car to 'start'. I'll sacrifice a few electric miles for not having to worry if the pack is to cold....just imagine your coworkers sayin nice car but wont start in the winter time. GM should allow me to have this choice so ...software update anyone? (and i still want that Hold Button).
 

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Great idea, Driverguy01. I'd like to see that as part of MyVolt stats as well! Check the battery temp from my computer, remote start the car if needed.
 

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So, with the clear caveat that I have not practiced real chemical engineering for quite some time, I thought it would be fun just to rough out some numbers. Obviously YMMV!!

Assume a 400 lb battery pack with a heat capacity of 0.75 Btu/lb-F (less than water). Say it starts at 30F and ends at -10F. That means the heat lost is around 400 * 0.75 * 40 = 12,000 Btu (Q = m * Cp * deltaT).

Now assume an overall heat transfer coefficient of 1 Btu/hr-ft^2-F (basic insulation against air), an area of 6 square feet, and a temperature difference of 60 F (damn cold). That means that heat will transfer at a rate of roughly 1 * 6 * 60 = 360 Btu/hr (q = U * A * deltaT).

Huge assumptions here, but it suggests that it would take about 30 hours, more than a day, for the battery pack to get from 30 F to -10 F.

Again, these numbers are very, very rough (and quite conservative).

Chris
 

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OK Slap, Here i go:I may be very wrong here but at -20C to -28C, things go cold fast! the pack has more than 6 square feet (4 sides to a square) now i wont argue with you, physics are so long ago it's not funny! from experience, getting in my car after a days work (12 hrs cause split shift) is a freezing experience to say the least, hell some cars starters just wont turn over, you cant even put your hands on the wheel it'so damn cold. the pack will freeze maybe a few times during winter. hope i'm wrong. i just think for the times i cant plug the car, it would protect itself...simple software update.
 

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Not Cold Enough Here!

At least I dont have to worry about extremely cold temperatures where I am. I would most likely never experience the "BATTERY TOO COLD, PLUG INTO WARM" message. Although the ICE may start when the battery temperature is high. If we go back to having 40+ degree days in summer then the thermal management system will have work to do lol


41 Degrees.JPG
 

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OK Slap, Here i go:I may be very wrong here but at -20C to -28C, things go cold fast! the pack has more than 6 square feet (4 sides to a square) now i wont argue with you, physics are so long ago it's not funny! from experience, getting in my car after a days work (12 hrs cause split shift) is a freezing experience to say the least, hell some cars starters just wont turn over, you cant even put your hands on the wheel it'so damn cold. the pack will freeze maybe a few times during winter. hope i'm wrong. i just think for the times i cant plug the car, it would protect itself...simple software update.
Right. I assumed most of the heat would be lost out the exposed bottom of the pack, and not up through the car. In fact, the battery should keep the car's interior above outside temperature, so long as the windows are rolled up! It like having a heat pack built into the floor.

I did assume ridiculously cold outside temperature. If I re-run the numbers with your outside temperature (-20 F) then things get better. The deltaT in the heat transfer equation would be more like 40, not 60, and that would cut the heat loss rate by 1/3.

Clearly it would be much better to get some real data. I like all of the ideas mentioned above!
 

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@ VoltinME,

If the Battery Too Cold, Plug In to Warm message is displayed on the Driver Information Center of the 2011 Volt, the vehicle will not start until the high voltage battery is warmed up...

Is this also true of the 2012 Volt? I agree that a battery temperature/remote warm-up option is an excellent idea.
 
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@ Adarondax,

Yes, it will be the same for the 2012 Volt.
 

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Discussion Starter · #19 ·
Thanks...this is good info. I am building my new garage just for this.
 

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A nugget of info here about what may constitute "extended periods of time". Right after I bought mine, I was in Europe for a month. I parked it charged, and a month later the SOC was about half. Apparently the battery self-drain rate amounts to about half a mile per 24h in July NYC area weather.

Extrapolating on this: two months of non use, at least in the summer, appear to be enough to deplete the battery completely.
 
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