A system for charging a battery from various three phase or single phase grid supply voltages includes a full wave bridge rectifier for receiving the AC supply voltage, two DC to DC converters for receiving unregulated DC output voltage from the rectifier, a first switch connected to a first input line of a first one of the two converters and a second switch connected to a first input line of a second one of the two converters, wherein each of the switches is set to a first position when the supply voltage is at a lower one of the varying voltage levels and to a second position when the supply voltage is at a higher one of the varying voltage levels.