Patent ID: 8530105

Claim:
A fuel cell system, comprising: a fuel cell; a first detection unit that is configured to detect an output current and an output voltage at an actual operating point in the fuel cell; a second detection unit that is configured to measure an impedance of the fuel cell and to measure an amount of voltage reduction caused by a resistance in the fuel cell based on the measurement result of the impedance and the output current; a third detection unit that is configured to detect an amount of voltage reduction caused by a polarization in the fuel cell; a fourth detection unit that is configured to detect an amount of reduction in an electromotive voltage of the fuel cell; an estimation unit that is configured to estimate current-voltage characteristics of the fuel cell based on a detection result by each of the detection units; a stoichiometry ratio detection unit that is configured to detect a stoichiometry ratio of an oxidant gas supplied to the fuel cell; a judgment unit that is configured to judge whether an amount of remaining voltage reduction, excluding the amount of voltage reduction caused by the resistance from the difference between the electromotive voltage of the fuel cell and the output voltage at the actual operating point, consists entirely of the amount of voltage reduction caused by the polarization or includes the combination of the amount of voltage reduction caused by the polarization and the amount of reduction in the electromotive voltage, based on the detected stoichiometry ratio of the oxidant gas; and an output section comprised of the estimation unit and the judgment unit configured to output current-voltage characteristics of the of the fuel cell and a judgment from the judgment unit; wherein the third detection unit is configured to detect the amount of voltage reduction caused by the polarization based on the amount of remaining voltage reduction when the amount of remaining voltage is determined as consisting entirely of the amount of voltage reduction caused by the polarization; and wherein the fourth detection unit is configured to detect the amount of reduction in the electromotive voltage based on the amount of remaining voltage reduction when the amount of remaining voltage reduction is determined as including the combination of the amount of voltage reduction caused by the polarization and the amount of reduction in the electromotive voltage and based on the detected amount of voltage reduction caused by the polarization.