Fuel cell system

A fuel-cell stack system, comprising:

• a stack of electrochemical cells separated by bipolar plates, each of the bipolar plates including an anode, a cathode, and an ion-exchange membrane;
• a fuel gas supply circuit and an oxidant gas supply circuit;
• a cooling circuit structured to enable a coolant fluid to circulate therein, the cooling circuit including (a) a secondary circuit and (b) a primary circuit that is smaller in size than the secondary circuit, the primary and secondary circuits being isolated from each other by a thermostatic valve;
• a micropump installed at an outlet of the stack, the micropump being structured to enable a volume of water inside the stack to be mixed;
• and
• a core temperature measurement device arranged to determine an internal temperature of a core of the stack,
• wherein the primary circuit is activated when the internal temperature rises above a predetermined threshold,
• wherein a pump, other than the micropump, is installed in the primary circuit,
• wherein when the primary circuit is activated, the pump is activated in a pulsed mode, and
• wherein when the internal temperature rises above a second predetermined threshold, the pump switches from operating in the pulsed mode to operating in a continuous mode.