On-line Measurement for Ohmic Resistance in Direct Methanol Fuel Cell by Current Interruption Method

Electrochemical impedance spectroscopy (EIS) is widely used in fuel cell impedance analysis. However, for ohmic resistance (R-Omega), EIS has some disadvantages such as long test period and complex data analysis with equivalent circuits. Therefore, the current interruption method is explored to measure the value of R-Omega in direct methanol fuel cells (DMFC) at different temperatures and current densities. It is found that R-Omega decreases as temperature increase, and decreases initially and then increases as current density increases. These results are consistent with those measured by the EIS technique. In most cases, the ohmic resistances with current interruption (R-iR) are larger than those with EIS (R-EIS), but the difference is small, in the range from -0.848% to 5.337%. The errors of RiR at high current densities are less than those of R-EIS. Our results show that the R-iR data are reliable and easy to obtain in the measurement of ohmic resistance in DMFC.