BMW 3 Owners & Service Manuals

BMW 3: Functions

The cooling system has 2 operating conditions, which result from its function:

  • Cooling OFF
  • Cooling ON

Cooling OFF operating condition

The "Cooling OFF" operating condition is active when the cell temperature is in or below an optimal range. This is generally the case if the vehicle is moved at moderate ambient temperatures and at low electrical power. The "Cooling OFF" operating condition is particularly efficient because no additional energy is required for cooling the high-voltage battery.

The components involved work as follows:

  • The electric A/C compressor is not in operation or runs at reduced power if only the vehicle interior needs to be cooled.
  • The combined expansion and shutoff valve at the high-voltage battery unit is closed.

Cooling ON operating condition

If the battery cells heat up to temperatures of approximately 86 ºF (30 ºC), cooling of the high-voltage battery unit starts. The SME control unit sends a cooling requirement to the IHKA control unit with 2 priorities. The IHKA decides whether the passenger compartment or the high-voltage battery unit is cooled or both are cooled. The cooling requirement may be refused by the IHKA in the event of a cooling requirement by the SME with low priority and a high cooling requirement in the vehicle interior.

However, the high-voltage battery unit is always cooled for a cooling requirement by the SME with high priority.

The IHKA requests electrical power for the EKK for cooling from the high-voltage power management in the Electrical Machine Electronics.

The components act as follows in "Cooling ON" operating condition:

  • The SME control unit requests a cooling requirement.
  • Following release by the IHKA the SME control unit activates the combined expansion and shutoff valve at the high-voltage battery unit. This valve opens and refrigerant flows into the high-voltage battery unit.
  • The electric A/C compressor is operational.

For drawing off and filling the refrigerant the "Drain/Fill refrigerant circuit" service function must be called up from the ISTA application. The combined expansion and shutoff valves are activated as they are closed in the de-energized state.

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