What effect does overcharging a lead-acid battery have?

Overcharging a lead-acid battery primarily destroys the positive plate due to excessive chemical reactions that occur when the battery is charged beyond its capacity. Lead-acid batteries consist of lead dioxide (PbO2) on the positive plate, sponge lead (Pb) on the negative plate, and an electrolyte of sulfuric acid. When overcharging occurs, oxygen evolves at the positive plate, leading to an increase in temperature and potential corrosion.

This degradation process can result in a significantly shortened battery life as the active material on the plates deteriorates. Moreover, overcharging can also cause the electrolyte to heat up and evaporate, potentially leading to the battery drying out and further damage. Therefore, maintaining the proper charging levels is crucial for the longevity and performance of lead-acid batteries.