Abstract: An on-board electrical system for a vehicle includes a first rechargeable constant voltage source (12), a second rechargeable constant voltage source (14), and a circuit breaker device (16) therebetween, including a first circuit breaker (18) and a second circuit breaker (20). Each circuit breaker (18, 20) permits current flow between input terminal (E1, E2) and output terminals (A1, A2) in both directions in a conductor state and permits current flow from the input terminal (E1, E2) to the output terminal (A1, A2) only in a diode state. The input terminal (E1) of the first circuit breaker (18) is connected to the first constant voltage source (12), the output terminal (A1) of the first circuit breaker (18) is connected to the output terminal (A2) of the second circuit breaker (20), and the output terminal (A2) of the second circuit breaker (20) is connected to the second constant voltage source (14).