Patent ID: 8158297

Claim:
A fuel cell system comprising: fuel cells; a supply flow path for supplying a fuel gas from a fuel supply source to the fuel cells; a variable gas supply device that regulates a gas condition of the supply flow path; a first control device that drives and controls the variable gas supply device; an off-gas flow path configured to release a fuel off-gas from the fuel cells to the outside through a discharge valve; a second control device that drives and controls the discharge valve; and a defect detection device that detects a valve opening defect of the discharge valve, wherein the defect detection device detects the valve opening defect of the discharge valve based on a gas supply amount increase amount Qinc=Qreq−(Qfc+Qcl), in which Qreq is the gas supply command amount based on a PI control rule for the variable gas supply device, Qfc is a fuel gas consumption in the fuel cells, and Qcl is a cross leak amount from an anode pole side to a cathode pole side in the fuel cells.