This same problem happens in evs where due to some problem the 12v discharges. When everything is working the 12v is charged up from the main battery bank. Tes

This same problem happens in evs where due to some problem the 12v discharges. When everything is working the 12v is charged up from the main battery bank. Tesla in the early days sometimes ran down the 12v and it wasn't that uncommon, there were problems with runs of batteries yielding poor ones; I think they had messed up software that wasn't charging the 12v enough, but they made changes to address that long ago. On my second ev, a rivian, I just had to have my 12 battery replaced. They said sometimes the 12v batteries just die on them.