Convenience charging electronics
The convenience charging electronics enable communication between the vehicle and charging station of the AC voltage supply in order to charge the high-voltage battery unit. The convenience charging electronics convert the AC voltage into high-voltage direct current voltage in order to charge the high-voltage battery unit in the vehicle. Charging of the vehicle takes place in parked position, normally overnight in the garage. Here the charging procedure must be adapted to the available grid power.
In addition, the convenience charging electronics have high-voltage connections for the electric A/C compressor and the electrical heating. This permits preheating/precooling of the vehicle as long as the charging cable is connected with the AC supply without energy being taken from the high-voltage battery unit. The convenience charging electronics also controls locking of the charging plug and charging socket cover. The lighting and display relating to the charging plug are also controlled by the convenience charging electronics.
Battery Charging Unit (BCU)
The charger unit for auxiliary battery is installed at the rear of the luggage compartment; it consists of a control unit and a unidirectional DC/DC converter. It connects the separate 12 V vehicle electrical system for the starter motor and auxiliary battery with the standard 12 V vehicle electrical system.
It is responsible for charging the auxiliary battery. The charger unit for auxiliary battery receives the target voltage with which the auxiliary battery is charged as a LIN message from the Digital Motor Electronics (DME). After the auxiliary battery has been fully charged, the auxiliary battery charging unit is switched off by the DME. The energy consumption in the vehicle electrical system can be reduced during the electric journey or when driving on a highway.
The advantage this system offers is the electrical isolation caused by the DC/DC converter in the charger unit for auxiliary battery. This electrical isolation prevents a voltage dip in the standard 12 V vehicle electrical system when the combustion engine is started.
The charger unit for auxiliary battery can detect when the 12 V vehicle electrical system is being charged via an external 12 V charger. Using this function, the charger unit can also charge the auxiliary battery when the vehicle is not awake but is being charged by an external charger (in the 12 V vehicle electrical system).