The aim of this work is the study of the effectiveness of different parameter estimation techniques for proton exchange membrane fuel cells (PEMFC) under normal operating conditions. The procedure for the estimation of the real time parameters described herein in good approximation meets the requirements posed regarding such techniques, i.e., to obtain data without interrupting the functioning of the fuel cell and to be as simple as possible. In this approach a fuel cell combined with a step-down voltage regulator system was analyzed and the potential relaxation was used to determine PEMFC electrochemical properties. A screening measurement technique was applied using the analysis of variance (ANOVA) to elucidate the effect of the different operating conditions on the obtained parameter, hence to validate the developed algorithm. The results show that the operating conditions of the step-down regulator device affect some parameters, but the weak correlations predict that the method can be used in real applications.