Fuel cell system and related control method

A controller (21) regulates a DC/DC (direct current/direct current) converter (13) to set the voltage level to be supplied from a secondary battery (7) to a load (6) at a value equal to or greater than the open voltage level of a fuel cell stack (1) during start-up of the fuel cell stack and set the voltage level supplied to the load through the DC/DC converter at less than the detected voltage level. The fuel cell stack is supplied with fuel and oxidant gases to voltage supplied to the load e.g. drive motor, electric compressor (3) installed on a fuel cell powered vehicle through a diode (11). Voltage is charged and discharged in the secondary battery. The DC/DC converter is connected to the fuel cell stack through the diode to convert voltage level, charge the secondary battery and supply converted voltage to the load. An independent claim is also included for a fuel cell system control method.