Heat issues, in particular, the temperature increase in a lead-acid battery during its charging has been undoubtedly a concern ever since this technology became used in practice, in particular in the automobile industry.
Thermal events in lead-acid batteries during their operation play an important role; they affect not only the reaction rate of ongoing electrochemical reactions, but also the rate of discharge and self-discharge, length of service life and, in critical cases, can even cause a fatal failure of the battery, known as “thermal runaway.”
It was found by calculations and measurements that there is a cooling component in the lead-acid battery system which is caused by the endothermic discharge reactions and electrolysis of water during charging, related to entropy change contribution.
Thus, under certain circumstances, it is possible to lower the temperature of the lead-acid battery during its discharging.
The aim of this study is to look at a less appreciated fact that during lead-acid battery discharge, an entropy-based phenomenon leads to a cooling effect, which may not be intuitively apparent as it is often negated by Joule heating due to large current flow.
Sulfuric acid in lead-acid batteries is usually a 30% aqueous solution in the fully charged state, so its entropy will be different. The entropy value for this diluted sulfuric acid is 128.1 J∙K −1 ∙mol −1 and it will significantly affect the conclusions about cell heat balance .