As the battery discharges, the active materials in the electrodes (lead dioxide for the positive electrode and sponge metallic lead for the negative) react with the sulfuric acid in the electrolyte to form lead sulfate and water. On recharge, the lead sulfate then converts back to the lead dioxide and metallic lead.

The Li-ion chemistry cannot accept even a trickle overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous. Float charging, however, is a useful option.