Abstract: An electrical receptacle is connected to the alternator of an automotive vehicle to permit connection thereto of a power tool. A switching circuit senses the presence of an electric current through the tool to actuate relays in the switching circuit to cause the alternator to operate in a high voltage mode wherein the alternator provides power at a voltage level suitable for operating the tool at such times that the engine of the vehicle is operating. A unidirectional current path is provided between the battery of the vehicle and the receptacle to enable operation of the switching circuit at such times that the engine is not operating while isolating the battery from electrical power generated by the alternator in the high voltage mode of operation thereof.

Abstract: An electric power generator incorporating an automobile alternator operable in a high voltage mode suitable for providing power for hand power tools and in a low voltage mode suitable for maintaining the charge of a battery which provides a field current for the alternator. A switching circuit, manually or automatically actuable to place the generator in the high voltage mode of operation, interposes a voltage regulator in the field current circuit and connects the output of the alternator to the battery to charge the battery when the generator is operated in the low voltage mode and interposes a variable resistor in the field current circuit and disconnects the battery from the output of the alternator to permit adjustment of the output voltage of the alternator when the generator is operated in the high voltage mode.