Patent ID: 7608354

Claim:
A fuel cell system, comprising: a fuel cell which generates electric power by being supplied with fuel gas and oxygen; an off-gas passage through which fuel gas discharged from the fuel cell passes; a gas/liquid separation device which is provided in the off-gas passage and which separates water from the fuel gas and accumulates the water; a discharge valve which is connected to the gas/liquid separation device and which can discharge the fuel gas to an outside of the fuel cell system along with the water accumulated in the gas/liquid separation device; and a controller that controls an opening/closing operation of the discharge valve, wherein the controller detects or estimates a change in pressure at a portion upstream of the discharge valve, decides a closing time at which an integral value that obtained by integrating an amount of change in the pressure at the portion upstream of the discharge valve with respect to time from when the discharge valve is opened or a parameter value corresponding to the integral value reaches a predetermined value, and closes the discharge valve at the closing time.