BMW 3 Owners & Service Manuals

BMW 3: Procedure after an accident

The safety concept of the high-voltage system ensures that, even during or after an accident, there is no danger to the customer, the rescue services or the service employee. The high-voltage system is automatically switched off in the event of an accident in such a way that no dangerous voltage is applied at those points on the high-voltage components which are accessible from the outside.

This deactivation is realized by an extended safety battery terminal. It contains an additional normally closed contact. This switch contact opens when the battery safety terminal is triggered at the same time as the positive battery cable is severed. Opening this switch contact causes the switch contactors in the high-voltage battery unit to open directly so that no more dangerous voltage can be fed into the high-voltage electrical system from the high-voltage battery unit. The Electrical Machine Electronics receives a crash signal from the Advanced Crash Safety Module (ACSM). The Electrical Machine Electronics then discharges the link capacitors immediately. The coils of the electrical machine are also short-circuited.

After an accident the safety battery terminal remains in the state described above such that the high- voltage battery unit is not operational. This means that the high-voltage system remains inactive even if PAD mode or the DRIVE vehicle condition is switched back on.

Before work is carried out on the high-voltage components of a G20 PHEV involved in an accident with activated safety battery terminal, the "Assessment of a vehicle involved in an accident" document in the ISTA workshop system must be completed.

Rescue disconnect

G20 PHEV, installation location of emergency separation point

A second rescue disconnect is necessary as a result of the requirements of the emergency services, which state that vehicles with an electrical drive system must have two separate rescue disconnects in the vehicle. The second separation point is always found opposite the high-voltage service disconnect in the vehicle. If the high-voltage service disconnect is located in the luggage compartment, the emergency separation point is then located in the engine compartment.

The emergency separation point is a line with terminal 30C. Terminal 30C supplies the switch contactor in the safety box with voltage. This line is cut through at the marked point to ensure that the switch contactors open. The rescue disconnect can be repaired after it has been cut through.


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