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I'm wondering about the 12 volt battery. Seems there's very little information on this in my 2014 owners manual. I presume it's the sealed type with no maintenance required, and that the on-board computer/s keep/s it charged by the main, high voltage battery. Just checking to see if this is the case or if there is something more that needs to be done or watched for. Maybe a yearly maintenance item for the dealer??
 

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There's no maintenance. It's an AGM type battery and sealed. Either it's good or it's not. (yea, it could get weak over time, that's still classified as bad.) If the car won't start and starts with a 12V jump, it's probably replacement time.
 

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The 12V battery is not recharged by the HV battery, at least for gen 1 Volts.

If you will not be using the car for weeks, you are asked to put the 12V battery on trickle charge.
 

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The 12V battery is not recharged by the HV battery, at least for gen 1 Volts.

If you will not be using the car for weeks, you are asked to put the 12V battery on trickle charge.
Well, it is charged by the HV battery via the APM when the car is on, which I assumed is what the OP was asking (but he wasn't explicit on this). Even when off, I think 2013+ will monitor the 12V battery occasionally if plugged in and charge it as needed... I could be wrong, but I think 2011-12 did not have this for some reason. My 2013 manual does say to use a trickle charger if the car will be sitting for over 4 weeks. For 4 weeks or less, just keep it plugged in normally.
 

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In other words, it works just like an ICE vehicle - the 12V battery is only charged when the car is running.
FWIW: When I was testing on my Gen1 if successfully plugged in and actively L1 charging there is @13VDC present on B+ even when the 12V AGM battery is then disconnected/removed from the circuit. Once the charging cycle is completed, this DC voltage that was present on B+ disappears. Of course you have to have the 12V AGM or equivalent present to even initiate L1/L2 charging cycle.
 

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Oh, and the first symptoms of the 12V starting to weaken are random crazy behavior of electronics that can't otherwise be explained. Fuel tanks suddenly reading as empty one drive then back up to 6 gallons? Nav Map lines on your backup camera? Engine Running Due To Temperature message that starts the engine then vanishes? All among the possible weirdness that comes with a nearly-dead 12V AGM.
 

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To clarify
All Gen1 cars have the 12V charged by the On-Board Charging Module (OBCM) when actively charging. This operation has been revised in Gen2 to be performed by the 14V Auxiliary Power Module (APM) as utilized by ALL Volt years when ON.

2011-12 Volts will NOT actively maintain the 12V battery SOC unless the the car is ON (via APM) OR plugged in AND actively charging (green charge LED ON) as described above (OBCM)

2013 and newer model (including Gen2) have an additional "Battery Maintenance Mode" (BMM) that will occasionally and regularly "wake up" the necessary content to check and if necessary "top up" the 12V AGM battery's SOC to mitigate the effects if certain parasitic drain elements (Onstar being one of them) that might affect the 12V SOC.

More complete details of the behavior of BMM can be found in the 12V charging section of Steverino's excellent FAQ here:
http://gm-volt.com/forum/showthread.php?5409-Auxillary-Battery&p=1292514#post1292514

More info on the Gen2 changes to the 12V charging system also found in FAQ here:
http://gm-volt.com/forum/showthread.php?5409-Auxillary-Battery&p=3346034#post3346034

I am currently confirming complete BMM information on the Gen2 cars but it currently appears it is idental to 2013+ Gen1 cars.

HTH
WopOnTour
 
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