The working principle of lead acid battery

The anode (PbO2) and cathode (Pb) in the lead storage battery are immersed in the electrolyte. 2V of electricity is generated between the two poles.

The chemical change in the discharge is that the dilute sulfuric acid will react with the active materials on the anode and cathode plates. Then a new compound “lead sulfate” is formed. Then it is released from the electrolyte, and the longer the discharge, the thinner the concentration of sulfuric acid.

The consumed component is proportional to the discharge volume. As long as the concentration of sulfuric acid in the electrolyte is measured, the discharge capacity or residual power can be known.

The chemical change during charging is on the anode plate during discharge. The lead sulfate produced on the cathode plate will be decomposed and reduced to sulfuric acid during charging. Lead becomes lead oxide, so the concentration of electrolyte in the battery gradually increases. The specific gravity of the electrolyte rises and gradually returns to the concentration before the discharge. This change shows that the active material in the battery has been restored to a state where it can be powered again. When the lead sulfate at both poles is reduced to the original active material, charging ends. The cathode plate produces hydrogen, and the anode plate produces oxygen.

When charging to the final stage, the current is almost all used in the electrolysis of water. Therefore, the electrolyte will be reduced, and it should be replenished with pure water at this time.