The anode (PbO2) and cathode (Pb) in the lead storage battery are immersed in the electrolyte (dilute sulfuric acid), and 2V electricity will be generated between the two electrodes. This is based on the principle of the lead acid batteries. After charging and discharging, the cathode, anode and electrolyte will be The following changes occur: (anode) (electrolyte) (cathode) 　PbO2 + 2H2SO4 + Pb = PbSO4 + 2H2O + PbSO4 (discharge reaction) 　 (lead dioxide) (sulfuric acid) (sponge lead) 　 the valence of Pb in PbO2 decreases, After being reduced, the negative charge flows; the valence of Pb in the spongy lead increases, and the positive charge flows. (Anode) (Electrolyte) (Cathode) 　PbSO4 + 2H2O + PbSO4=PbO2 + 2H2SO4 + Pb (charge reaction) (must be in the electrified condition) (lead sulfate) (water) (lead sulfate) 　The first lead in lead sulfate The valence of the lead increases and is oxidized, and the positive charge flows into the positive electrode; the valence of the lead in the second lead sulfate decreases and is reduced, and the negative charge flows into the negative electrode. 1. Chemical changes during discharge: When the battery is connected to an external circuit for discharge, the dilute sulfuric acid will react with the active materials on the anode and cathode plates to form a new compound, lead sulfate. The sulfuric acid component is released from the electrolyte through discharge. The longer the discharge, the thinner the concentration of sulfuric acid. The consumed component is proportional to the discharge amount. As long as the concentration of sulfuric acid in the electrolyte is measured, that is, the specific gravity is measured, the discharge amount or residual power can be known. 2. Chemical changes during charging: As the lead sulfate produced on the anode and cathode plates during discharge will be decomposed and reduced to sulfuric acid, lead and lead dioxide during charging, the concentration of the electrolyte in the battery gradually increases. That is, the specific gravity of the electrolyte rises and gradually returns to the concentration before discharge. This change shows that the active material in the battery has been converted to a state where it can be powered again. When the lead sulfate at the two poles is converted into the original active material, That is equal to the end of charging, the cathode plate produces hydrogen, and the anode plate produces oxygen. At the final stage of charging, the current is almost used in the electrolysis of water, so the electrolyte will be reduced. At this time, pure water should be added.