Charging and Discharging of Lead Acid Battery.


Discharging of Lead Acid Battery.

The positive plate, or anode, of a fully charged cell, is PbO2, whereas the negative plate, or cathode, is Pb. H2SO4 is decomposed into positive H2 and negative SO4 ions when the cell discharges, that is, when it transfers electric current via the external load. H2 ions migrate to the anode as the current in the cell flows from cathode to anode, while SO4 ions move to the cathode. H2 mixes with the oxygen in PbO2 at the anode (PbO2), and H2SO4 strikes Pb to produce PbSO4.

Anode reaction: PbO2 + H2 + H2SO4 → PbSO4 + 2H2O

SO4 reacts with Pb at the cathode to form PbSO4.

Cathode reaction: Pb + SO4 → PbSO4

A discharged battery has the following characteristics:

  1. Both the anode and the cathode became PbSO4, which has a whitish color.
  2. The specific gravity of the acid falls as a result of the production of water.
  3. The cell’s voltage drops.
  4. The cell gives off energy.


Charging of Lead Acid Battery.

The H2 ions travel to the cathode and the SO4 ions to the anode when the cell is recharged, resulting in the following changes:

At Cathode: PbSO4 + H2 → Pb + H2SO4

At Anode: PbSO4 + 2H2O → PbO2 + 2H2SO4

As a result, the anode and cathode are once again PbO2 and Pb.

A charged battery has the following characteristics:

  1. The anode turns dark chocolate brown (PbO2), while the cathode turns grey metallic lead (Pb).
  2. The specific gravity of H2SO4 increases as a result of water intake.
  3. An increase in voltage has occurred.
  4. The cell absorbs the energy.

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