The Fuel Cell DC/DC converter is used to alternatively supply submarine DC loads from alternatively by a fuel cell. Furthermore, the fuel cell can be used to charge the battery. The main function of the FCCD is to match the wide ranging e fuel cell voltage to that of the e wide range battery voltage. For our existing design, the fuel cell voltage range is: 160 up to 360Vdc and the battery voltage range is 450 up to 750Vdc. The total output power of the FCCD is 240kW supplied by two fuel cells.