BMW 3 Owners & Service Manuals

BMW 3: Voltage supply

BMW 3 Series G20 (2018-2026) Training manual / Low-voltage Vehicle Electrical System / Voltage supply

The 12 V vehicle electrical system of the G20 PHEV is essentially the same as the electrical system of the G20. The main difference lies in the fact that the power supply is no longer by the alternator, but by the high-voltage electrical system. The high voltage of the high-voltage battery unit is converted to the lower voltage (approximately 14 V) using a DC/DC converter in the Electrical Machine Electronics (EME). The electric voltage supply of the 12 V vehicle electrical system is thus no longer dependent on the engine speed of the combustion engine when driving.

Another difference is that the starter motor and auxiliary battery form an independent 12 V vehicle electrical system, which is connected to the standard 12 V vehicle electrical system by the charging unit for the auxiliary battery (Battery Charge Unit (BCU) ).

System overview

Voltage supply
G20 PHEV, system wiring diagram, 12 V voltage supply

  1. Digital Motor Electronics (DME)
  2. Integrated supply module (PDM)
  3. Starter motor
  4. Power distribution box, engine compartment
  5. Jump start terminal point
  6. Electric motor
  7. Electric Motor Electronics (EME)
  8. Power distribution box, inner
  9. Body Domain Controller (BDC)
  10. Charger unit for auxiliary battery (Battery Charge Unit)
  11. Hybrid-specific fuse
  12. Power distribution box, rear
  13. Hybrid power distribution box
  14. Safety battery terminal 2 (SBK2)
  15. Auxiliary battery
  16. Intelligent battery sensor 2 (IBS2)
  17. Intelligent Battery Sensor (IBS)
  18. Battery
  19. Safety battery terminal (SBK)
  20. Power distribution box, front left

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