Yes, change the battery, the old one is toast. My 12v battery lasted 7 years, and I changed it before it could potentially leave me stranded. But the volt does all sorts of whirring and clicking when you leave it alone, so having it plugged in might have helped you from losing your 12v battery so soon. Then again, getting a new battery every 4 years isn’t all that bad. All cars need regular maintenance.
My 2017 Volt (42 month old) just went dead. I was able to recharge it via the charge terminals under the hood and jumper cables. I read in one of the forums that once these batteries die, they are unreliable and it is best to replace them. I keep it parked in a warm garage with daytime temps around 95F. I only have 10k miles on it because it has been parked at my vacation home. I have been going there 4-5 times per year for 7-10 days at a time. The car has been parked usually without EVSE charger attached for up to 3-4 months at a time.
1. Should I leave it plugged into my EVSE, when I leave for up to 4 months? It is connected to a Juicebox EVSE that can be scheduled to limit charging to a specified time period during the day. Alternately, I could use the controls in the Volt to limit charging.
2. If the transportation mode was suitable it would probably be too complicated for my property manager or wife to turn off. I am not keen of disconnecting the - terminal of the battery in the trunk for the same reason. My property manager occasionally needs to drive it while I am gone so my solution needs to be as simple as possible.