Model 3 12v battery dead

[SylvainG]

Would leaving Sentry on for the night at -30C raise the temperature of the battery enough to charge it? If not, you'll deplete your 12V battery with no way to recharge it.

 

[android04]

Would leaving Sentry on for the night at -30C raise the temperature of the battery enough to charge it? If not, you'll deplete your 12V battery with no way to recharge it.

I don't think Sentry Mode uses enough energy to warm the Tesla lithium ion low voltage battery, but I wouldn't worry about it. I'm sure Tesla has some way to draw a burst of energy from it in order to warm it and be able to charge it. Otherwise, I'm sure Tesla will just not power down the DC to DC converter to keep the car from dying of a depleted low voltage battery.

 

[SigNC]

based on the tear down it can discharge at -20c and charge at -10c so wouldn't be too hard to discharge it at say... -20c and warm it up to -10c right? Below -20c is a mystery though as you get into a bit of a catch22. You can't draw power to close HV contactors so there is no way to warm it anyway even if it had a heater. I guess maybe the car could draw the battery down and charge it repeatedly if it saw it was below -20c outside until the HV pack maybe got too cold as well? (it of course could also warm itself up along the way to put that off longer)

 

[iwannam3]

NO, they would require a very different BMS which is in the main battery pack to supply charging voltage which is very different than lead acid. I would think the BMS would need different hardware components, but maybe? they could do it with software magic?

The latest Teslas are coming out with Lithium 12V batteries. These are supposed to last much longer than the old ones. Can you get the new 12V batteries from Tesla?

Watch Ingenerix at 7:14 where he opens the new Li battery. Look at all the circuitry, the voltage in not 12, it is 16 volts fully charged!