Organic expanders play an important role in the lead-acid battery. This study presents the design of an electrochemical method which evaluates the influence of some commercial expanders on the performance of the negative plate. Examination is made of different commercial expander formulations which are prepared in the laboratory under carefully controlled conditions. In order to compare their influence on the behaviour of the negative plate, potential step and cyclic voltammetric techniques using high-potential polarization are performed. The results allow the selection of those expander additives which exert the best electrochemical effect on high-rate discharge reactions at negative plates.