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Energy needed to keep pack warm

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So winter has definitely hit during the last two weeks here and it made me think about the need for a electrical outlet at work, or maybe a new work that has a n outlet available :tongue:

I have a relatively short drive to work 26km each way and even when traffic is bad, like the first day of a snow storm, it takes 1.5 hours to travel each way, but still easy even with the standard 160 mile pack. However I never considered the impact of the car not being plugged in and it warming the battery in minus 20 degree celecius weather for 10 hours while at work. Any thoughts on what energy usage may be like to keep the battery warm and at what temperature it needs to keep the battery at?
 
I asked a similar question to a sales guy about being parked in the sun on a hot day. In that situation, he mentioned that about a mile of range is used per day to regulate the battery's temperature. With really cold weather, I imagine it's possibly a few times more than that...maybe up to 5 miles of range a day?
 
I don't believe that any battery power is used to heat the pack; it's heated by utility power before charging begins when it's really cold.

When the battery is very cold it can be damaged if charged so, at -20c the regen no longer charges the pack and upon charging the first order of business is to heat the pack; pulsing blue charge light.

In my experience, it takes many hours to cool down after charging or driving. You'll know if it's too cold after work if you've lost regen. It'll be back though after a few miles of driving as the pack warms up from use - self heats.
 
I don't believe that any battery power is used to heat the pack; it's heated by utility power before charging begins when it's really cold.

When the battery is very cold it can be damaged if charged so, at -20c the regen no longer charges the pack and upon charging the first order of business is to heat the pack; pulsing blue charge light.

In my experience, it takes many hours to cool down after charging or driving. You'll know if it's too cold after work if you've lost regen. It'll be back though after a few miles of driving as the pack warms up from use - self heats.

Actually, in my experience regen turns off at only a few degrees below freezing, if the car has cold soaked.
 
I think the answer is "yes". The following seems to confirm that:

No mentioning of battery heating/warming here;
http://webarchive.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf
...Note the tubes and manifold extending out of the battery pack at its lower long edge. These are used to circulate cooling fluid (a 50/50 mix of water and glycol) throughout the pack via sealed fluid paths. This enables us to keep the cells thermally balanced. This extends the life of the battery pack and also has numerous safety benefits...
...This cooling architecture avoids “hot spots” which can lead to failures in large battery modules...
...the battery logic board communicates with the vehicle to initiate battery cooling..
Mention of warming while charging (while plugged in) here;
http://www.teslamotors.com/roadster/technology/battery
...In general, Lithium-ion cells cannot be charged below 0 degrees Celsius, which would theoretically prevent charging in cold environments. To overcome this cold weather charging obstacle, the Roadster is designed with a heater to warm the cells (when plugged in) to an appropriate charging temperature. If there were no battery pack heater, drivers living in cold environments would have difficulty charging and experience stunted driving performance...
... If the temperature rises above a set threshold, the air conditioning unit sends chilled coolant through the pack. Similar to the radiator fan of ICE-powered cars, the chilled coolant continues to circulate after the motor has been turned off to keep the temperature at an appropriate level. Cooling the pack enables a driver to quickly charge immediately after hard driving in hot climates. Without such a cooling system, recharging in hot weather would be delayed after each drive...
 
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I'm curious what the heat capacity of the pack is and how thermally isolated it is from the environment. Then one could estimate how much energy is used to get the pack to temperature.

Can you determine how much energy is used from the logs?