Patent ID: 8241800

Claim:
A fuel cell system comprising: a polymer electrolyte fuel cell; an anode off gas passage; a cathode off gas passage separate from the anode off gas passage; a resistance sensor configured to detect an internal resistance of the fuel cell; a dew point sensor associated with the anode off gas passage and configured to detect a dew point of anode off gas from the fuel cell; and a controller programmed to execute an electrolyte membrane hydration control according to a relationship between the detected internal resistance and the detected dew point, wherein the controller is programmed to execute the electrolyte membrane hydration control if a dew point variation per resistance variation ratio changes to a smaller value upon crossing a boundary defined by a predetermined cell resistance, wherein the dew point variation per resistance variation ratio is a variation amount in the detected dew point divided by a variation amount in the detected internal resistance and multiplied by −1.