Charging of Lead Acid Battery

Charging of Lead Acid Battery Points : Charging of Lead Acid Battery, Indications of Fully Charged Cell For charging a battery a d.c. supply of voltage little higher than the battery voltage is applied across the battery. The care should, be taken that positive terminal of battery should be connected to positive terminal of supply and negative plate to negative terminal of supply. The current passes from positive plate to the negative plate inside the cell the chemical reaction is an follows. At Negative plate: PbSO₄ + 2H⁺ = Pb + H₂SO₄ At Positive plate: PbO₂ + S0₄ + 2H₂0 = PBO₂ + 2H₂S0₄

The changes occurs during charging is as below: (i) The positive plate changes to lead peroxide (Pb02), which is dark chocolate brown in colour.
(ii) The negative plate changes to spongy lead which is slate grey in colour.
(iii) The voltage per cell increases from 1 .8 volt to 2.1 volt.
(iv) The specific gravity of each cell rises from 1.180 to 1.280.
The cell stores electrical energy in form of chemical energy.

Indications of Fully Charged Cell 1. Colour Plate The colour of positive and negative plate changes to dark brown and slate grey. 2. Specific Gravity Specific gravity increases from 1.180 to 1.280. 3. Gassing Gassing will occur on both plates of the cell. 4. Voltage per cell Rises form 1.8 volt to 2.1 volt at no load.