The following is a recent exchange I had with Volt vehicle line director Frank Weber concerning battery temperature control in the Chevy Volt.
Does the battery always have some electronics running, even when the car is turned off?
No, there is a real sleep mode.
Did you hear about former CEO Martin Eberhard noting his Tesla Roadster was constantly burning energy when it sat in the garage unused?
Yes, his refrigerator. We don't have this problem.
What we also will do is we will condition that battery for a certain period. When its plugged in and charging, and its really really cold, then you would probably spend a fraction of your grid energy just to keep your battery conditioned so that you can leave your garage or house in very very low temperatures, driving electrically.
What if you leave your Volt outside in the extreme cold?
You could still do this. The battery is fully insulated. Keeping the battery temperature for a while. To keep it just above freezing it can drive electric. Also the car will be smart. If you don't use your car at some point you don't want to spend energy anymore. At that point it will just stop conditioning.
The car will know that? Say if you leave it unused for a week?
No one will want to condition the battery for a week. What's happening at low temperatures depends on what the state of charge is, we haven't seen any major sensitivities. This car could sit there for two weeks, but without conditioning it again, it certainly wont start on electric. The engine would start and condition the battery for a few minutes.
So is there a delay when the car decides whether to start on gas or electric?
It would know this within a fraction of a second. The moment you open the door, the calculation starts, what is the battery temperature, what is the outside temperature and how should the car start.
So the gas engine will then heat the coolant?
It will propel the car and it will condition the battery. The moment you are running the engine you have the electric heater running in the battery.
So there is an electric heater in the battery?
Yes, you can chill and heat the battery.
Do you need to keep the battery at room temperature the whole time it is operating?
You don't have to condition it to that level.
Can you say how low a temperature can the battery go on at?
No. A certain operating window that you have. You don't have to always keep it at 71 degrees F. Ideally that is the temperature you would like it because that is where you have the maximum power output of the battery and you have the best life expectations.