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.