Patent ID: 7597977

Claim:
A diagnostic method for a fuel cell comprising a plurality of cells, comprising: supplying an anode of the fuel cell with hydrogen or a hydrogen-containing gas; supplying a cathode with an inert gas or vacuuming the cathode; detecting an amount of the inert gas supplied to the cathode; measuring a gas pressure at the anode; measuring a gas pressure at the cathode; measuring a voltage of each cell under a condition in which the hydrogen or the hydrogen-containing gas is supplied to the anode of the fuel cell and the inert gas is supplied to the cathode or the cathode is vacuumed, wherein an operation state of the fuel cell is changed when measuring the voltage of a cell; introducing a cooling medium into a passage within the fuel cell; changing a temperature of the cooling medium when measuring the voltage of each cell; and determining an amount of cross-leak based on the measured gas pressure at the anode, the measured gas pressure at the cathode, and on a measured voltage of each cell, wherein in the determining step, an amount of hydrogen cross-leak of each cell is determined from the measured voltage of each cell generated based on a principle of a hydrogen concentration cell, and wherein the amount of cross-leak is calculated based on the pressure of the hydrogen-containing gas at the cathode, on the total pressure of the inert gas supplied to the cathode, and on the amount of the inert gas supplied to the cathode.