Abstract: To provide a dual-voltage network for the on-board electrical system of automotive vehicles, for example to provide a higher voltage for starting of the vehicle and a normal on-board voltage for operation of vehicle appliances such as lamps, fans, motors, and the like, while using only a single voltage regulator to control the charge voltage for the vehicle battery, a voltage doubler circuit is provided which is connected to the on-board network by a diode and a coupling capacitor connected to an a-c output of a vehicle alternator, the diode being connected between the d-c output and the rectifier connected to the alternator and the capacitor so that a voltage regulator, connected to the d-c output, can accurately control the output voltage of the alternator.