Patent ID: 8900769

Claim:
A counter-freeze control method for a fuel cell system, the fuel cell system comprising: a fuel cell having an anode to which fuel gas is supplied, and a cathode to which oxidant gas is supplied; a first shut-off valve connected to and disposed upstream from the fuel cell, the first shut-off valve having a first valve body; a second shut-off valve connected to and disposed downstream from the fuel cell, the second shut-off valve having a second valve body; a cathode control unit for sealing and unsealing the cathode by using the first shut-off valve and the second shut-off valve, the method comprising the steps of: stopping an electro-chemical reaction, which has been previously under way, from progressing in the fuel cell; closing the first shut-off valve and the second shut-off valve to seal the cathode; measuring temperature in the fuel cell; determining whether the cathode control unit performs a counter-freeze-scavenging process based on the measured temperature, residual water remaining in the anode and the cathode being discharged by supplying oxidant gas to both the anode and the cathode in the counter-freeze-scavenging process; unsealing the cathode by opening the first shut-off valve and the second shut-off valve; maintaining the first valve body and the second valve body open; and performing the counter-freeze-scavenging process, wherein the first shut-off valve and the second shut-off valve remain in the same state during the counter-freeze-scavenging process and after the counter-freeze-scavenging process.