An electric car has a 12 volt battery too, and according to the reports this is the part that fails most often. If it goes flat or weakens, the car shows random electrical faults, does not wake from sleep, or refuses to charge at all: the main traction battery can be full and still nothing starts. Behind it there is often not the battery itself but the DC/DC converter, which should feed it from the high voltage circuit. The reports give 25,000 to 35,000 km.

The symptom (will not start, will not charge) is far more frightening than the cause. The cheap 12 V battery is often mistaken for an expensive traction battery fault.