FUEL CELL SYSTEM HAVING IMPROVED STARTING UNDER FREEZING CONDITIONS

The invention relates to a fuel cell system, comprising: at least one fuel cell; a cooling device; at least one temperature sensor; and a control unit; wherein the cooling device comprises a coolant path for the flow of a coolant, a coolant pump, a heat releasing device, and a bypass, which can be operated by means of a bypass valve and which is parallel to the heat releasing device. A control unit is designed such that it senses the coolant outlet temperature or the coolant inlet temperature, identifies a first rising phase of the measured temperature during a start-up phase of the fuel cell system, monitors the measured temperature for a plateau after the first rising phase has been identified, identifies a second rising phase following the plateau, and, during the plateau, reduces a conveyed volumetric flow rate of the coolant in the coolant path and/or increases a current flow in the at least one fuel cell and/or reduces a cell voltage.