A method of connecting a plurality of controlled vehicle electrical system branches of a vehicle control unit for performing the method as well as the vehicle power supply

It is a control unit (40) for controlled exchange of electric power between a first, a second, a third and a fourth vehicle electrical system branch described a vehicle electrical system of a vehicle (10; 30 11; 20;). This comprises a first, second and third switching means (50) and a first, second, third and fourth port (41; 42; 43; 44) (for connection to the first, second, third and fourth vehicle electrical system branch 10, 20 , 30) are arranged. The first switching device (50) is between the first terminal (41) and the fourth port (44) is connected, the second switching device (51) is connected between the fourth terminal (44) and the third port (43), and said third switching device (52) between the second terminal (42) and is connected to the third terminal (43). Further, a vehicle on-board network is described with a control unit and with the first to fourth board network branches.