Patent ID: 8663858

Claim:
A fuel cell system having a fuel cell stack that generates electric power by electrochemical reaction of reaction gases fed to the fuel electrode and oxidant electrode, the fuel cell system comprising: a fuel gas feeding device that feeds fuel gas; a plurality of auxiliary devices comprising: an oxidant gas feeding device that feeds oxidant gas; and a cooling water feeding device that feeds cooling water; a control device programmed to perform the following fuel conservation operation: when a load demanded of the fuel cell stack falls below a prescribed level, shutting down the auxiliary devices; drawing a current, having a substantially constant value greater than zero, from the fuel cell; and causing the fuel gas feeding device to feed fuel gas to the fuel cell at a non-zero flow rate; and a voltage detecting device that detects the voltage of said fuel cell stack, wherein said control device resets operation from said fuel conservation operation to an idle operation when said voltage during said fuel conservation operation is lower than a prescribed level, wherein the idle operation comprises: turning on the auxiliary devices; and increasing the flow rate of the fuel gas; wherein when a transition is made to said fuel conservation operation, said control device delays setting the stack current for said fuel conservation operation until after the shutdown of said auxiliary devices so that said stack voltage does not exceed a voltage in said idle operation.