Voltage–time behavior of a polymer electrolyte membrane fuel cell stack at constant current discharge

Empirical equations were developed to describe the voltage–time behavior of polymer electrolyte membrane fuel cell (PEMFC) stacks at constant current discharge. When either ambient temperature or discharge current is too high, the experimental voltage–time curves exhibit rapidly falling cell voltage within a short discharge time. Various experimental voltage–time curves have been fitted very well with empirical equations at different discharge currents and ambient temperatures. The effect of parameters of the empirical equations on the shape of voltage–time curve is also analyzed. Inadequate mass-transfer is likely a reason for the voltage falling down rapidly, and polymer electrolyte membrane dehydration is responsible for the inclination of the voltage–time curves. The empirical equations are helpful for forecasting and explaining the long-term discharge performance of the PEMFC stacks.