Using AC when the Model S car is "off"?

[radiantMemory]

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!

 

[Yggdrasill]

Don't worry about it. The regular 12V battery is charged from the main battery whenever it falls below a specific state of charge. This happens seamlessly without you noticing.

 

[zentage]

you can activate AC from your IOS or android app. Preheating or precooling the car is awesome
It drains from the main battery - hence you will loose range.

 

[GSP]

I ran the A/C in my Model S for over 3 hours in 90+ degree F heat while watching the eclipse. It used about 10 miles of range from the battery. There is much less noise and heat rejection from the car compared to an ICE vehicle, which is very nice.

GSP

 

[Brass Guy]

The app will turn on climate control for about 30 minutes. Its great for getting the car ready.

There's also the unofficial "camping mode." (Put the car in Neutral, apply the parking brake using the touch screen.) The car will stay on indefinitely, including climate control. You can stay in the car, or exit and lock the car. During the eclipse road trip (had some food and a small cooler in the car) I left the AC on for 8 hours in the sun, 90F outside. It used about 30 miles of rated range. It worked out wonderfully.

 

[mknox]

FWIW, the a/c compressor runs directly from the HV main battery pack while the fan and controls works from the 12v system. The car keeps the 12v battery topped off from the main battery via a DC-DC converter which kicks in periodically as needed (even when the car is parked and off).