I’m discovering that the 12V battery needs to be monitored outside of normal daily use. It appears the Chevy Bolt (I own a 2017) doesn’t maintain the 12V battery at it’s nominal voltage while plugged into the EVSE over extended periods of time.

I Installed a 12V battery monitor due to the numerous 12V battery related issues for Bolt posted in several forums. ANCEL BM300 Wireless

Screenshots of the Ancel app for the entire month of March 2020:

(Browse left/right to see all of the images for each day of the month of March)

March 1st - 12th: Normal daily use. The spikes in voltage is normal. It occurs when you turn on the car and it senses the voltage and begins charging it. I’m not sure what happened on March 3rd in regards to the voltage drop. It’s never done it before.

March 13th - 31st: Parked and plugged in. Keep an eye on the voltage as it slowly drops each day

March 27th - I installed the Deltran Battery Tender Jr. charger later that evening. Battery voltage has been stable ever since.

If you don’t want to purchase a battery tender, you can unplug your car, turn it on for at least an hour, turn it off, and plug it back in. I would recommend doing this every week.

Reddit Post discussion:

https://www.reddit.com/r/BoltEV/comments/ft76km/potential_12v_battery_maintenance_issue/