According to the preceding analysis, a maximum value of the efficiency of the fuel cellstack will appear in the low current range or the low power range. In the high current rangeand high power range, the efficiency of the fuel cell stack will decrease with the increase of the fuel cell stack current and power. The reason for the difference between the practical efficiency and the theoretical efficiency of the fuel cell stack is the hydrogen utilization ratio is too low in the low current range or the low power range.