Change in Specific Gravity of the Acid Electrolyte in the Lead-acid Battery Upon Repeated Charge-discharge Cycles

Abstract

When a lead-acid battery deteriorates, the specific gravity of the acid electrolyte gradually decreases from the initial value (1.28) to 1.18-1.20. However, in our laboratory's study, the specific gravity value increased from 1.28 to 1.32-1.36 after the charge. This is very unusual. Our various results have been reported regarding this behavior. The specific gravities of batteries after discharging also gradually (but faster than the case of after charging) increased with repeating charge-discharge cycles. One of the reasons for accounting these phenomena is thought to be due to the production of fine particles of Pb and PbO₂ the recovery form the sulfation by repeating cycles of low-rate charge and high-rate discharge accompanied with the use of additives such as organic polymers.