[T-Keith]

Just an update. There were no good used onboard chargers locally, apparently these get damaged a lot and many yards don't pull them. I ended up finding a damaged one, and took it apart and combined with mine. (wires and plugs). Reprogrammed with the vcx(a hassle) and bleed the coolant and it works!

 

[hellsop]

Well, the battery is not a 12-volt battery it's special to the car 14 volts and that explains a lot

It's not that special. The same battery is in a lot of 2010s Toyotas and Mazdas, a couple Hondas and smaller cars in VW's lines (including Audis)

 

[supertsar]

Followup - Took it to Chevy - they said it is the on board charger. $2500 for the part and it will take weeks to get. It may have been a coincidence, but I ran the preheat option right before the on board charger died (it heats both seats, runs the defrosters, heats the interior... maybe too much strain for an old charger?). I don't want to go thru this expense with the 10 year old propulsion battery a ticking time-bomb. So I will keep it in hold mode and switch to mountain mode when it gets low as I contemplate my next vehicle. Not sure what the implications are of driving the volt around without ever being able to plug in... will it work?

Just a follow up - had to pass an Illinois emissions test today (with the on board charger kaput) and it did! Despite the charge related codes. Was worried I might enter some dystopian bureaucratic nightmare if it failed. Also tried driving around in hold mode and the battery eventually went up to almost a full charge (to 9 bars from 6). Then drove in normal until 4 bars. Then switched to mountain mode and it immediately charged back up to 5 bars - which I assume equals 50% of usable battery. Pleasantly surprised as I had read it would charge to only 40%. So far so good.