12 Volt Battery SOC

[MCarl33]

I’ve seen a lot of posts on the 12 volt battery but none that I recall as to how high of a SOC percentage the BMS will charge the 12 volt battery . I have a 2021 Premium MME and it won’t charge above 78 % SOC. I’m running the car in Park and turning everything off I can. It starts off at 14.8 volts and then drops down to 12.4 volts when it reaches 75 % SOC. I’m using CarScanner software with VeePeak OBD to monitor 12Volt battery. Is it still charging the battery at 12.4 volts and eventually will it reach 80% or higher?

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[Teslaeata]

14.8V is the charging Voltage. When your measured Voltage drops to 12.4V is likely the LVB SoC when the charger turns off.

Should charge to 100% but may not complete full charge until driving.

BMS will usually provide as much charge as necessary.
I wouldn’t worry too much at that.

Having all this information isn’t always healthy as trying to interpret it and then misinterpreting it often sparks all sorts of fears which otherwise would not exist.

If you are still concerned, I’d suggest monitoring LVB SoC when you’ve driven a good distance and if still unsure have the battery condition checked out by dealer is what’s do.

 

[Mach-Lee]

I’ve seen a lot of posts on the 12 volt battery but none that I recall as to how high of a SOC percentage the BMS will charge the 12 volt battery . I have a 2021 Premium MME and it won’t charge above 78 % SOC. I’m running the car in Park and turning everything off I can. It starts off at 14.8 volts and then drops down to 12.4 volts when it reaches 75 % SOC. I’m using CarScanner software with VeePeak OBD to monitor 12Volt battery. Is it still charging the battery at 12.4 volts and eventually will it reach 80% or higher?

BMS does go to 100%, but that can take 2-3 days of charging to reach (top end is VERY slow). When you report 12.4V, the car is not charging the battery at that point. It's in discharge. Remember the auto shutdown timer will shut the car off after 30 minutes unless you disabled it (and it resets to ON every time the car is turned on).

You may have some other issue, you may want to send me your VIN so I can take a look.

 

[JimmyMachE]

Apart from Aux voltage and SOC, you may want to check another sensor - 'LVB Current'. Negative value means the 12V battery is being discharged.

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