Fuel cell system

A fuel cell system comprising:

• a first fuel cell to which a fuel gas and an oxidant gas are supplied, the first fuel cell including a plurality of first unit cells stacked together;
• a second fuel cell to which a fuel gas and an oxidant gas are supplied, the second fuel cell including a plurality of second unit cells stacked together;
• a first voltage detector connected to the first fuel cell;
• a second voltage detector connected to the second fuel cell;
• and
• a controller configured to control the first fuel cell based on a detection result of the first voltage detector, and control the second fuel cell based on a detection result of the second voltage detector, wherein
• each of the first unit cells includes a first electrolyte membrane, a first anode catalyst layer provided on a first surface of the first electrolyte membrane, and a first cathode catalyst layer provided on a second surface of the first electrolyte membrane,
• each of the second unit cells includes a second electrolyte membrane, a second anode catalyst layer provided on a first surface of the second electrolyte membrane, and a second cathode catalyst layer provided on a second surface of the second electrolyte membrane,
• the first electrolyte membrane and the second electrolyte membrane are made of the same material, and have substantially the same thickness,
• the first anode catalyst layer and the second anode catalyst layer are made of the same material, and have substantially the same amount per unit area,
• the first cathode catalyst layer and the second cathode catalyst layer are made of the same material, and have substantially the same amount per unit area,
• the first voltage detector is configured to detect voltage of the first unit cells for every “N” unit cells on average,
• the second voltage detector is configured to detect voltage of the second fuel cell as a whole, or detect voltage of the second unit cells for every “M” unit cells on average, where “M” represents a number that is larger than “N”, and
• the controller is configured to determine whether any of the second unit cells is in a fuel deficiency state, based on the detection result of the first voltage detector, when a predetermined condition under which states of the first fuel cell and the second fuel cell are regarded as being close to each other is satisfied.