Teslas automatically keep the 12v topped up from the HV system. But like any car battery they can die and eventually won’t take a charge at all. What they should so is have a bypass circuit you can activate to let the whole 12v subsystem pull directly from the HV system as long as the car is not in drive. The issue is that the HV battery needs a physical disconnect in an accident which is why they have the 12v battery in the first place.
Teslas automatically keep the 12v topped up from the HV system. But like any car battery they can die and eventually won’t take a charge at all. What they should so is have a bypass circuit you can activate to let the whole 12v subsystem pull directly from the HV system as long as the car is not in drive. The issue is that the HV battery needs a physical disconnect in an accident which is why they have the 12v battery in the first place.