A method of operating a fuel cell system

The present invention relates to a method of operating a fuel cell system (2), the vehicle equipped in one with a tachograph (6) and an internal combustion engine (3) (1) is arranged and which when switched internal combustion engine (3) for supplying power at least one electrical component (10) of the vehicle (1). The operating method comprises the following steps: - a control unit (4) of the fuel cell system (2) communicates with the tachograph (6). - The control unit (4) is obtained during a driving operation of the vehicle (1) with switched off the fuel cell system (2) by the tachograph (6) an expected break start time point of the driving operation following, legally prescribed and / or the driver of the vehicle (1) planned operational break, wherein the internal combustion engine (3) is turned off. - The control unit (4) is determined for this operating break a system start timing for the fuel cell system (2) so that a start-up procedure of the fuel cell system (2) terminates the pause start time and the fuel cell system (2) is operable, when the fuel cell system (2) is started at the calculated startup time becomes.