Lead Acid Batteries are leading the industry because they are cheap, have a large current and surge capability.
Basic Components are,
Positive plate: This is covered with a paste of lead dioxide.
Negative plate: This is made of sponge lead.
Separator: This is an insulating material between the two plates, but it allows the electrolyte and the ions into it to enable conduction without the two plates touching.
Electrolyte: This consists of water and sulphuric acid
These constituents are all contained within a plastic container.
Working
The diluted sulfuric acid H2SO4 molecules break into two parts when the acid dissolves. It will create positive ions 2H+ and negative ions SO4-. As we told before, two electrodes are connected as plates, Anode and Cathode. Anode catches the negative ions and cathode attracts the positive ions. This bonding in Anode and SO4- and Cathode with 2H+ interchange electrons and which is further react with the H2O or with the water (Diluted sulfuric acid, Sulfuric Acid + Water).
Charging
To charge the battery, we need to apply a voltage greater than the terminal voltage. So to charge a 12.6V battery, 13V can be applied.
The same chemical reactions which we described before. Specifically, when the battery is connected with the charger, the sulfuric acid molecules break into two ions, positive ions 2H+ and negative ions SO4-. The hydrogen exchanges electrons with the cathode and becomes hydrogen, this hydrogen reacts with the PbSO4 in cathode and forms Sulfuric Acid (H2SO4) and Lead (Pb). On the other hand, SO4- exchange electrons with anode and become radical SO4. This SO4 reacts with PbSO4 of anode and creates the lead peroxide PbO2 and sulfuric acid (H2SO4). The energy gets stored by increasing the gravity of sulfuric acid and increasing the cell potential voltage.
At the anode: PbSO4 + 2H2O => PbO2 + SO42- + 4H- + 2e-
At the cathode: PbSO4 + 2e- => Pb + SO42-
Overall: 2PbSO4 + 2H2O => PbO2 + Pb + 2H2SO4
Discharging
The sulfuric acid is in the diluted form with typically 3:1 ratio with water and sulfuric acid. When the loads are connected across the plates, the sulfuric acid again breaks into positive ions 2H+ and negative ions SO4. The hydrogen ions react with the PbO2 and make PbO and water H2O. PbO starts reacting with the H2SO4 and creates PbSO4 and H2O. On the other side SO4- ions exchange electrons from Pb, creating radical SO4 which further creates PbSO4 reacting with the Pb.
At the anode: PbO2 + SO42- + 4H- + 2e- => PbSO4 + 2H2O
At the cathode: Pb + SO42- => PbSO4 + 2e-
Overall: PbO2 + Pb + 2H2SO4 => 2PbSO4 + 2H2O