Patent ID: 8541142

Claim:
A fuel cell system comprising: an oxidizing gas supply valve provided on a flow path for supplying oxidizing gas which is air to a fuel cell stack; an oxidizing gas exhaust valve provided on a flow path for exhausting the oxidizing gas from the fuel cell stack; a pressure detecting unit which detects a cathode pressure value which is a pressure in a flow path between the oxidizing gas supply valve and the oxidizing gas exhaust valve and including an oxidizing gas flow path in the fuel cell stack; a stop processor which closes the oxidizing gas supply valve and the oxidizing gas exhaust valve when an operation of the fuel cell stack is stopped; and a judging unit programmed to receive pressure information from the pressure detecting unit and determine whether there is an operation deficiency of the oxidizing gas supply valve and the oxidizing gas exhaust valve based on a stop-time cathode pressure value when the operation of the fuel cell stack is stopped and a startup cathode pressure value when the fuel cell stack is started up after the operation of the fuel cell stack is stopped, wherein the startup cathode pressure value is taken after a predetermined time period has elapsed from the time that the fuel cell stack is stopped, wherein the predetermined time period is greater than or equal to a total time period of a time period in which a cathode pressure is reduced due to reaction of the fuel gas and remaining oxygen in the oxidizing gas, a time period in which the cathode pressure is temporarily increased due to the presence of the fuel gas after the remaining oxygen in the oxidizing gas is depleted, and a time period in which the cathode pressure is reduced due to reduction of nitrogen remaining in the oxidizing gas.