AC impedance characteristics of a vehicle PEM fuel cell stack under strengthened road vibrating conditions

• Strengthened vibration has a great influence on the AC impedance characteristics.
• The ohmic resistance rises linearly and ultimately reaches a growth of 7.139%.
• During the test, the charge transfer resistance varies obviously.
• The cell positions have a significant impact on the ohmic resistance.

Electrochemical impedance spectroscopy is used in this paper to investigate the performance of the fuel cell stack and single cells under long-term vibrating conditions on strengthened roads. During strengthened road vibration test, the electrochemical impedance spectra of fuel cell stack and several cells in the stack are measured nine times at regular intervals. Parameters of a Randles-like equivalent circuit are fitted to the experimental data. The classical Randles cell is extended by changing the standard plane capacitor into a constant phase element so that the quality of fit is improved. The results of the electrochemical impedance analysis indicate that the ohmic resistance of the fuel cell stack is nearly linear with the vibration time and reaches a growth of 0.035695% per hour. While the charge transfer resistance of the fuel cell stack during strengthened vibration test ascends after it falls down firstly, and finally tends to be stable. The influence of cell position on the AC impedance is also studied, and the results of which show that the cell position has a significant impact on the ohmic resistance.