Patent ID: 7192667

Claim:
A method for controlling a fuel, cell system including a fuel cell stack, an air pumping device and a hydrogen supply device, both coupled to the fuel cell stack to supply the air and hydrogen thereto, respectively, and a hydrogen exhaust valve coupled to the fuel cell stack for relief of the hydrogen therefrom, the method comprising the steps of: (1) initiating a start-up routine to start supply of the air and hydrogen to the fuel cell stack through an air supply conduit and a hydrogen supply conduit, respectively; (2) detecting hydrogen pressure inside the hydrogen supply conduit; (3) based on the detected hydrogen pressure, selectively opening/closing a hydrogen valve mounted to the hydrogen supply conduit for controlling hydrogen flow rate through the hydrogen supply conduit; (4) detecting output voltage and current of the fuel cell stack; and (5) selectively driving the air pumping device mounted to the air supply conduit, in a pulse width modulated manner, for controlling air flow rate through the air supply conduit in accordance with the detected output voltage of said fuel cell stack, wherein, when the detected output voltage is lower than a preset lower voltage level indicative of a presence of an unwanted liquid accumulated in the fuel cell stack, controlling the air pumping device to increase the air flow in the air supply conduit to a maximum air flow rate to thereby remove unwanted liquid accumulated in said fuel cell stack, maintaining said maximum air flow rate during a first predetermined period of time, and controlling the air pumping device to resume to a normal flow rate upon said first predetermined period of time is over.