The present invention discloses a dual-voltage vehicle electric system in which a dual-battery vehicle electric system is integrated. In this dual-voltage vehicle electric system, two conventional vehicle batteries are used and are generally operated while connected in series. The series circuit provides the supply voltage for the vehicle electric system at a relatively high voltage for high-power loads. In order to implement an emergency start, both batteries, specifically a starter battery (BS) and a vehicle electric system battery (BB), are connected in parallel. In the case of a defective generator (G) or DC/DC converter (1), an emergency operating supply via battery is possible. The switching of a starter commutation device (U) which is arranged in the connection between the starter battery (BS) and the vehicle electric system battery (BB) is carried out by means of a control device (2) which receives input signals from sensing devices at the starter (S), generator (G), DC/DC converter (1), the starter battery (BS), the vehicle electric system battery (B) and an ignition switch (ZS) and a starter switch (SS) and correspondingly adapts the actuation.