Patent ID: 8617753

Claim:
A fuel cell system comprising: a fuel cell comprising a plurality of cells stacked on one another and supplied with a gas for power generation, the gas unused for the power generation to be discharged out of the fuel cell; a circulation flow path through which the gas discharged out of the fuel cell is resupplied to the fuel cell; a voltage sensor configured to measure voltages of the respective cells of the fuel cell; a variable flow rate circulation pump provided on the circulation flow path to circulate the gas through the circulation flow path, wherein the circulation pump is operative to adjust a flow rate of the gas in the circulation flow; a valve provided on the circulation flow path to discharge the gas in the circulation flow path to the outside of the circulation flow; and a controller for controlling the circulation pump and the valve, the controller being programmed to control the variable flow rate circulation pump to increase the flow rate of the gas in the circulation flow path if some of the measured voltages are below a predetermined range which includes an average value of the measured voltages of the respective cells, and to open the valve if all of the measured voltages are within the predetermined range and the average value of the measured voltages of the respective cells is lower than a predetermined value.