Battery System, Hybrid Drive: Description and Operation

GF83.40-P-2009LEH Battery Cooling System, Function

Function requirements, general
^ Circuit 61
^ Automatic air conditioning switched on
^ Electric refrigerant compressor (A9/5) switched on

Circuit 61 is required to start the electric refrigerant compressor. Then cooling is possible even without engine speed (stop mode).

The status of circuit 61 is provided by the ME-SFI [ME] control unit (N3/10) via chassis CAN (CAN E) and forwarded from central gateway control unit (N93) via interior CAN (CAN B) to AAC [KLA] control unit (N22/1).

Battery cooling system function, general
The battery management system control unit (N82/2) monitors the temperature of the high-voltage battery (A100g1). This is integrated into the high-voltage battery module (A100).
For this, the battery management system control unit evaluates the data of the high-voltage battery cell temperature sensors (A100b2) for recording the current high-voltage battery temperature and requests, when required, cooling output via drive train sensor CAN (CAN I) from the ME-SFI [ME] control unit. This sends the request to the central gateway control unit and from there via interior CAN to the AAC [KLA] control unit.

If cooling is required, the battery management system control unit opens the high-voltage battery cooling system shutoff valve (Y19/1) and the refrigerant flows through the evaporator integrated into the high-voltage battery module. Thermal energy is thereby extracted from the refrigerant and the high-voltage battery cools. If the air conditioning is manually switched off, the high-voltage battery is not cooled. If the temperature of the high-voltage battery is too warm (T > 42 °C), the air conditioning is automatically switched on and operated with the settings from before it was switched off.
For this purpose, the battery management system control unit sends the switch-on request via drive train sensor CAN (CAN I) to the ME-SFI [ME] control unit. This sends the request via chassis CAN to the central gateway control unit. The central gateway control unit routes the switch-on request via interior CAN to the AAC [KLA] control unit.

The electric refrigerant compressor is then actuated by the AAC [KLA] control unit. The AAC [KLA] control unit sends a corresponding signal via interior CAN to the central gateway control unit for this purpose. This routes the request via chassis CAN to ME-SFI [ME] control unit. The ME-SFI [ME] control unit then actuates the electric refrigerant compressor via drive train sensor CAN.
In the opposite direction, the electric refrigerant compressor sends the current status to the AAC [KLA] control unit.

As long as the high-voltage battery still requires cooling, the air conditioning cannot be switched off again (block function: the deactivation is undone after t = 2 s). The air conditioning remains on after cooling the battery.