Patent ID: 8715872

Claim:
A fuel cell system including a fuel cell stack, a fuel gas supplying unit for supplying fuel gas to the fuel cell stack, and an oxidizer gas supplying unit for supplying oxidizer gas to the fuel cell stack, wherein the fuel cell stack includes a plurality of stacked cells each formed by interposing an electrolyte membrane between a fuel electrode supplied with the fuel gas and an oxidizer electrode supplied with the oxidizer gas, the fuel cell system comprising: a current control device that extracts a current from the fuel cell stack; a voltage sensor that measures voltages from a plurality of different cells of the fuel cell stack; and a controller electrically coupled to the fuel gas supplying unit, the oxidizer gas supplying unit, current control device, and the voltage sensor; wherein the controller is programmed to cause the fuel gas to be supplied to the fuel electrode without supplying the oxidizer gas to the oxidizer electrode at a time of initiating operation of the fuel cell stack, wherein the controller is programmed to extract through the current control device a current sufficient to inhibit deterioration of the electrolyte membrane after a minimum value detected by the voltage sensor becomes zero volts or more, wherein the controller is programmed to determine weather to finish the current extraction based on variations of the current amount extracted by the current control device, and wherein the controller is programmed to cause the oxidizer gas to be supplied to the oxidizer electrode to start producing electricity in the fuel cell stack once the current extraction has finished.