On-board chargers (OBC) are charging devices used to charge the batteries of electric vehicles. They are installed in the vehicles, ensure authentication of the e-vehicle at the charging station, convert the alternating current of the charging station into direct current, provide communication between the vehicle and the charging station, and handle battery management.
In line with automotive industry standards, on-board chargers are housed in metallic enclosures. The connectors to the charging station and the battery are extremely robust. Functionally, an on-board charger consists of a rectifier, which converts the single- phase alternating current or three-phasealternating current coming from the charging station into direct current, and a DC/DC converter, which provides the correct charging voltage for the batteries.
OBC units have different power classes depending on the mains voltage and the three-phase AC. Common power classes are 3.6 kW at 230 V AC and 16 A AC. With three-phase supply, the power values are 11 kW and 22 kW. From these values, the charging times for the car batteries can be calculated.
Via the built-in battery management system, on-board chargers ensure that batteries are charged quickly and in a way that is gentle on the battery. As far as communication between the charging station and the on-board charger is concerned, the latter are equipped with standardized communication protocols according to IEC 61851 and ISO 15118. They exchange charging parameters and information on payment procedures via the corresponding protocols. Some OBC units are smart and can also take over the energy feed into smart grids, namely when the car batteries take over buffer functions of the power grid.