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The propulsion battery in most electric cars (certainly Teslas) is disconnected by a relay when the car is off. So the amount of powered stuff isn't any higher

by tlb 7y ago

The propulsion battery in most electric cars (certainly Teslas) is disconnected by a relay when the car is off. So the amount of powered stuff isn't any higher than gas cars. Teslas also have a 12V battery to bootstrap the system and run accessories when the main power is off, though it's smaller than a typical ICE battery because it doesn't have to crank an engine. I don't think you can predict from theory which will have higher fire rates. All the fires are due to small flaws in the details, so it's a question of design and manufacturing carefulness.

alasdair_ 7y ago
>when the car is off Does it count as "off" when the car periodically wakes up when parked to do everything from check for updates to warming/cooling the batteries or cabin? (Not trolling, I can't find the actual answer.)
- esotericn 7y ago
  Nope. My car can drain the HV battery via recording video etc. It's certainly not solely powered by the 12V as it'd be flat within the day.
- 13of40 7y ago
  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.

by tlb 7y ago

alasdair_ 7y ago

>when the car is off Does it count as "off" when the car periodically wakes up when parked to do everything from check for updates to warming/cooling the batteries or cabin? (Not trolling, I can't find the actual answer.)

esotericn 7y ago
Nope. My car can drain the HV battery via recording video etc. It's certainly not solely powered by the 12V as it'd be flat within the day.
13of40 7y ago
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.