4 ms·

Also, if the little 12-volt runs down, will it recharge itself from the main one?

• kwhitefoot 7y ago
  Yes.
• goodcanadian 7y ago
  I can only speak for the Leaf, but much like a petrol/gasoline car, the 12V battery is only charged when the car is on (and when the car is actively being charged). It is entirely possible to run down the 12V battery if you leave the car parked long enough without it being turned on. Once the 12V runs down far enough, you are no longer able to turn the car on (or charge it) as the 12V powers the contactors for the main battery. I have had to jump start my Leaf due to a bad 12V battery.
• makomk 7y ago
  In the case of Teslas, yes. The power drain on the 12V system when parked from all the computers etc is apparently so high that they have to recharge it periodically from the main battery. The service life of the 12V battery is pretty terrible because of this. They also have battery heaters that switch on periodically to keep the main battery warm, which I think are powered by the main battery. Basically, if you leave your Tesla sitting in a garage for a few days you can expect the main battery to be connected and used at least some of that time (maybe all of it) even though it has a contactor to disconnect it entirely.