Patent ID: 8435687

Claim:
A contactor failure detecting apparatus for use in a fuel cell system comprising: a fuel cell operated to generate power by reaction of a fuel gas and an oxygen-containing gas; a load driven by an output from said fuel cell; a contactor that is opened and closed in order to electrically connect and disconnect said fuel cell with respect to said load, said contactor having one end connected to an output side of said fuel cell and another end connected to said load; a DC/DC converter capable of voltage variable control or current variable control, having one end thereof connected to a load side of said contactor and another end thereof connected to an energy storage device; and a control device, wherein said control device is configured to transmit an opening command to said contactor while said contactor is in a closed state, thereafter lowers the voltage on a load side of said DC/DC converter, and detects a closing failure of said contactor, when the voltage of the fuel cell changes, when the current flows out from the fuel cell, or when the voltage on the load side of the DC/DC converter does not become smaller than the voltage of the fuel cell.