Low-voltage battery
Stores energy for vehicle electronics and starting-related functions.
In a protected compartment; location depends on the BMW.
Battery chemistry and management must match the vehicle; electric cars also need low-voltage power.
A small energy reservoir that wakes the car.
Slow starting or failure to wake can reflect charge level, battery health, connections or charging control.
Batteries and connections depend on age, charging and usage. Control units are diagnosed by faults, power and communications.
A fuse or connection differs from a coded controller. Identify the cause before replacing an expensive electronic module.
A charged BMW traction battery does not guarantee that its separate low-voltage system can wake the car.
BMW low-voltage systems across combustion, hybrid and electric models; equipment varies.