A fuel cell system cooperating with a rechargeable battery (18) mounts a
fuel cell (12) as a source of motive power in an electric vehicle with an
electric motor. The fuel cell system and the rechargeable battery (18)
supplies the electric motor with electrical power. The fuel cell system
also includes a reformer (11) as a source of hydrogen hydrogen-containing
gas supplied to the fuel cell (12). The fuel cell system comprises a
temperature sensor (19) for measuring the temperature (Tb) of the
rechargeable battery and a controller (16) for controlling the response
characteristics (mainly the response characteristics of the reformer) of
the fuel cell system based on the measured temperature (Tb). The
controller (16) calculates a response time of the fuel cell system based
on the measured temperature, and controls the supply of
hydrogen-containing gas to the fuel cell in response to the calculated
response time.