electrochemical impedance spectroscopy for investigation of different losses in 4-cells short stack with integrated humidifier and water separator

electrochemical impedance spectroscopy (eis) is a suitable and powerful diagnostic testing method for fuel cells (fcs) since it is non-destructive and provides useful information about fc performance and its components. in this study, for the first time, a 500w cascade type 4 cells stack with integrated humidifier, water separator and internal manifolds was designed, fabricated and tested. the diagnostic test was conducted by eis. the effects of dead end and open end modes of the stack impedance spectra are studied. the results suggested that ohmic resistance of the single cell decreased with increasing current density due to the greater effect of hydration of membrane. the results of the electrochemical impedance revealed that the gas operating mode had significant impacts on electrochemical impedance of the stack. when the stack was tested on dead end mode, the charge transfer resistance of the stack decreases dramatically and its influences on mass transfer resistances are negligible.