How does AC work? In a regular ICE vehicle, in order for AC to work (and not just the fan) you would have to turn on the car/engine. What about in the Model S? I don't want to drain its battery (apparently there are 2 batteries. Obviously the lithium ion battery pack underneath the car, and apparently another battery like the ones you see in traditional ICE vehicles. I don't want to drain the other "normal battery" and would only like to use the Li-Ion battery pack. Car in question is a Signature 2012 Tesla Model S. Thanks!