This paper presents the results of tests on a fuel cell systemwith a proton exchange polymermembrane (PEM), describing the principle of operation of the PEM fuel cell. The advantages and disadvantages of fuel cells are also described, along with a presentation of the various types of fuel cells. The paper presents an external characteristic of a fuel cell as well as the curve of power utilization has been presented. Three loss areas result from the external characteristics as follows: activation losses, ohm losses, and mass transport losses. Further, it is necessary to consider the influence of the temperature of a working cell. The external characteristic of a fuel cell stack were determined by measurements. The paper further examines the effect of purging the anode on the functioning of the stack, the dynamics of that functioning, the electrical efficiency of the stack, and the impact of the coefficient of excess air on the working of the stack.