Patent ID: 8541141

Claim:
A fuel cell system, comprising: a fuel cell having a fuel electrode to which a fuel gas is supplied and an oxidant electrode to which an oxidant gas is supplied, the fuel cell configured to generate electricity via a reaction between the fuel gas and the oxidant gas during a normal generation mode; a gas discharge unit for discharging a discharge gas from the fuel electrode of the fuel cell; an external load for receiving power from the fuel cell; and a controller unit operable configured to: while the fuel cell is operating in the normal generation mode, stop supply of the fuel gas and the oxidant gas to the fuel cell to enter a first idle stop mode from the normal generation mode responsive only to a condition that a driving power does not need to be supplied to the external load from the fuel cell; and each time the driving power needs to be supplied to the external load from the fuel cell while operating in an idle stop mode including the first idle stop mode: restart the supply of the fuel gas and the oxidant gas to the fuel cell to end the idle stop mode and return to the normal generation mode; calculate a length of an idle stop prohibition period, the length having a maximum time value dependent on a duration of the idle stop mode; begin the idle stop prohibition period upon the return to the normal generation mode; upon the return to the normal generation mode, re-enter into the idle stop mode responsive to the condition that the driving power does not need to be supplied to the external load from the fuel cell only if the idle stop prohibition period has lapsed; and calculate a correction time value that is dependent on at least one operating parameter of the fuel cell system after restarting the supply of the fuel gas and the oxidant gas, wherein the length of the idle stop prohibition period is a difference between the maximum time value and the correction time value.