OEM 12v battery lasts for 7 months

[asian_xl]

2019 M3 based performance here. Replaced the 12v in April at Tesla service center, but 12v warning msg came out this week.
voltage meter at cigarettes light port shows the battery is at 14.1v (of course I can't tell whether it is voltage directly from the main battery or not).

Whether our 12v can use trickle charger or it has to be replaced?

 

[jjrandorin]

Any chance that the short lifetime on your 12v is due to the additional stuff you have hooked up there (power frunk, power trunk, additional lighting etc)?

 

[davewill]

2019 M3 based performance here. Replaced the 12v in April at Tesla service center, but 12v warning msg came out this week.
voltage meter at cigarettes light port shows the battery is at 14.1v (of course I can't tell whether it is voltage directly from the main battery or not).

Whether our 12v can use trickle charger or it has to be replaced?

14v is almost certainly the charging system output and not the voltage output of the battery. It's always possible you got a bad battery, but I'm thinking more along the lines that @jjrandorin is and some of your accessories are drawing the battery down when the car is off. You can certainly trickle charge the battery, or take it to a shop to be load tested to see whether the battery is actually bad or not.

 

[Resist]

Even if the accessories he has drains down the 12 volt battery, then wouldn't the high voltage battery keep the 12 volt battery charged up? To me it seems like he just got a bad battery, even though that's pretty rare, I've never had that happen ever.

 

[P3dStealth]

Even if the accessories he has drains down the 12 volt battery, then wouldn't the high voltage battery keep the 12 volt battery charged up? To me it seems like he just got a bad battery, even though that's pretty rare, I've never had that happen ever.

Yes and no. The battery would be fine and the car would keep it charged...but the way the car monitors the battery health it would trigger the 12v warning message. Essentially it sees that the battery as unhealthy because it is needing to be topped off more often than it should. It sees it as unable to maintain it's charge over whatever period of time. The issue was first noticed by people hardwiring dash cameras.

Power frunks and trunks don't cause the issue. It's likely they have it programmed in their control units to go into a low power sleep mode.

He has a lot of upgrades on his car. Power frunk, trunk, led strips, upgraded stereo etc.. very nice car but something may be staying powered on while the car goes to sleep. Maybe the led lights in the frunk stopped turning off. You wouldn't know because it's closed.

 

[asian_xl]

Noted. Will first get a switch for the LED strip. Never heard a problem when people installed it.