BMW 3 Owners & Service Manuals

BMW 3: 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


     Start-up system

    Starter motor The combustion engine B46 can be started via the conventional starter motor and the electrical machine. The following table shows when and under which conditions the respective start

     Terminal control for driving readiness

    Terminal control from driver's view Vehicle condition - DRIVING Vehicle condition - RESIDING Vehicle condition - PARKING Transitional condition for establishing driving readiness, ending driv

     Bus Systems

    The bus systems of the G20 PHEV are based on the bus systems of the G20. All the main and sub-bus systems of the G20 are also used in the G20 PHEV. Compared to the bus systems of the G20,


     Programmable memory buttons

    General information The iDrive functions can be stored on the programmable memory buttons and called up directly, for instance radio stations, navigation destinations, phone numbers and menu entries or pages in the Integrated Owner's Manual. Settings are stored for the driver profile currently used.

     Engine compartment

    Overview Jump-starting, positive battery terminal Oil filler neck Coolant reservoir, auxiliary cooling Coolant reservoir, engine Jump-starting, negative battery terminal Vehicle identification number Filler neck for washer fluid Hood Safety information Warning Improperly executed work in

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