Fuel cell system and fuel cell powered vehicle

A fuel cell system adapted to generate an electric power by supplying an anode gas and a cathode gas to a fuel cell, the fuel cell system comprising:

• an external load connected to the fuel cell;
• a voltage sensor configured to detect an output voltage of the fuel cell;
• and
• a controller programmed to:
• adjust the generated electric power of the fuel cell in accordance with electric power consumption of the external load;
• control humidity of an electrolyte membrane in the fuel cell on the basis of the generated electric power of the fuel cell;
• increase the humidity of the electrolyte membrane when the fuel cell generates the electric power;
• determine whether a cross leakage amount increases or not on the basis of a voltage difference between an output voltage detected by the voltage sensor before the humidity of the electrolyte membrane is increased and an output voltage detected by the voltage sensor after the humidity of the electrolyte membrane is increased;
• and
• determine whether the output voltage of the fuel cell drops or not on the basis of a reference voltage defined in advance in accordance with an output current of the fuel cell and the detected output voltage,
• wherein the controller is programmed to start the determination whether a cross leakage amount increases or not in a case where the output voltage of the fuel cell drops.