As canehdian pointed out, I have confirmed the Lear 3.3kW on-board charger also supplies @13VDC to the AGM when my 2013 is actively plugged in and charging. This voltage is removed once the charging cycle is complete.The car has a DC-DC converter that charges the 12V battery off of the HV battery.
I think that both 2 & 3 did not exist prior to 2013 models. So 2011 and 2012s only charged while turned on like an ICE vehicle.For a 2014 it is charged in any one of the following states:
1) vehicle is powered ON (just like any other car when on, it simulates an alternator and charges the battery from 12V power source with ~15V and then drops to ~13.x)
2) when actively charging the main high voltage battery, 12V battery may be charged as well
3) when plugged in and not actively charging the HV battery, 12V will be periodicially checked and charged as required.
Scenario 3 did not exist prior to 2014 and may be the reason for many users having to prematurely replace their batteries.
We'll know in a couple years when 2014s pass the 4 year mark (when many early ones had to be replaced).
Very simple to confirm if your Volt is also charging the 12V AGM while plugged into L1/2 and charging:I think that both 2 & 3 did not exist prior to 2013 models. So 2011 and 2012s only charged while turned on like an ICE vehicle.