Patent ID: 8728677

Claim:
A fuel cell system comprising: a fuel cell control unit, the fuel cell unit programmed to: perform a cell voltage lowering prevention processing to supply a predetermined amount of oxidizing gas to a cathode of a fuel cell when a cell voltage of the fuel cell is below a predetermined lower limit voltage, and judge degradation of an electrolyte membrane of the fuel cell based on an amount of oxidizing gas supplied to the fuel cell during a low efficiency operation in which reactant gas is supplied at predetermined intervals, wherein the fuel cell control unit is programmed to judge that the electrolyte membrane of the fuel cell is degraded when an actually measured amount of oxidizing gas supplied to the cathode of the fuel cell is larger than an estimated amount of oxidizing gas supplied to the cathode, and wherein the fuel cell control unit is programmed to estimate the estimated amount being estimated from an output current of the fuel cell.