BMW 3: Coordinating the charging procedure

Coordination for starting and ending the charging procedure is performed by the high-voltage power management in the EME.

The following actions required by the customer at the start of the charging procedure:

• Adjust the desired charge current level in ampere
• Set the start time for charging
• Connect the charging cable.

G20 PHEV, menu for setting the charging parameters

After the charge current level has been defined, using the controller and the menu in the Central Information Display (CID) the customer can set and adjust the start time for charging in the vehicle.

An immediate start of charging after connecting the charging cable, or up to four departure times, by which the charging procedure must be completed, can be selected.

If a departure time is set, a time frame for charging with a reasonable electricity rate can additionally be set.

When the customer connects the charging cable connected to the AC voltage network, the convenience charging electronics wakes up the control units in the vehicle electrical system (if they have not already been woken up by another event). A wake-up line wired to the BDC control unit is used for this. Subsequently, the convenience charging electronics check the functional prerequisites for charging, and receive information on the safety-relevant conditions via the K-CAN5. These checks are summarized in the following list:

• Driving readiness off AND
• Parking lock engaged AND
• Charging cable connected (proximity) AND
• Communication with EVSE OK (pilot) AND
• High-voltage system active and trouble-free.

When all prerequisites for charging are satisfied, the high-voltage power management in the EME requests a charging power from the convenience charging electronics and starts the charging procedure. The EME control unit sends not only setpoint values for the charging power, but also specifies limit values for the maximum charging voltage and the maximum charge current. These values are based on the current condition (e.g. state of charge and temperature) of the high-voltage battery unit and on the power requirement of the rest of the vehicle electrical system (e.g. for climate control). The EME control unit cleverly implements these setpoint values, i.e. it takes into consideration not only the setpoint values, but other marginal conditions. These include the actual status of the Electrical Machine Electronics (fault, temperature), as well as the current level restricted by the AC voltage network and the charging cable.

The voltage is applied to phase L1 only after communication between the vehicle (KLE) and EVSE via the pilot line has been successfully started. This also gives further protection for customers and Service employees against the dangers of electricity.

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