Abstract: The invention relates to a battery unit (10) for use on an on-board power system (50) of a motor vehicle, comprising a battery module (20) and a battery management system (40) for monitoring and regulating the battery module (20). In this context, a communication unit (30) is detachably connected to the battery management system (40), which communication unit (30) has a receiver unit for receiving data from the battery management system (40), a conversion unit for converting the data received by the battery management system (40), and a transmission unit for transmitting converted data to a control device of the motor vehicle.

Abstract: The invention relates to a battery unit for use on an electrical system of a motor vehicle, comprising a battery module and a coupling unit (30). The coupling unit has a first and a second connection (31 and 32), a first and a second DC converter (41 and 42). The first DC converter (41) allows a bidirectional current flow between the connections (31, 32), the second DC converter (42) allows a current flow from the first connection (31) to the second connection (32). The battery unit comprises a control system. The control system controls the DC converter. The invention also relates to a method for operating the battery unit on a motor vehicle's electrical system. A coupling current (1k) flowing through the coupling unit (30) is measured. When the coupling current (1k) flows from the first connection (31) to the second connection (32) and falls short of a first threshold value, the second DC converter (42) is connected and the first DC converter (41) is disabled.