Benefit of increasing the organic expander dosage on the high temperature performance of the negative electrode of lead–acid batteries

Organic expanders function in the negative electrode of lead–acid batteries to promote the development of fine crystal sponge lead upon formation and to preserve this high surface area structure by preventing coarsening of crystals upon cycling. Organic expanders also serve to protect the negative active material from passivation during discharge or on open circuit by preventing the formation of an impervious non-conducting film of lead sulfate. The deleterious effect of a high temperature service environment on the life of the lead–acid battery and the negative electrode is well known. In this paper, we investigate the effect of Vanisperse A organic expander content on the capacity and life of the negative electrode of flooded lead–acid SLI batteries designed to be negative electrode limiting. The low rate capacity and cold cranking performance of batteries designed to be negative electrode limiting remained essentially unchanged upon increasing the organic expander dosage from 0.25 to 0.50% on weight of lead oxide in a negative mixture. Battery life, however, when tested according to the SAE J240 protocol, increased 25% at 41 °C, and 20% at 75 °C. When tested according to the SAE J2185 protocol at 50 °C, battery life increased 15%. No adverse effects were observed. This work shows that increasing the Vanisperse content has a beneficial effect on the high temperature service life of the negative electrode.