A hydrogen fuel cell system (100) for charging a battery (116) of an electric vehicle, includes at least one tank (102) for storing hydrogen under pressure. A combined heat exchanger and air engine (104) expands the pressurized hydrogen and converts the expanding hydrogen into mechanical energy. A plurality of fuel cells (106) receive the expanded hydrogen for supplying heat to the heat exchanger and air engine (104) and supplying a first current for charging the battery (116). A generator (108) generates a multi-phase voltage in response to the mechanical energy. A electrical power converter (110) responsive to the multi-phase voltage provides a second current for charging the battery (116).