Construction and working of lead acid battery used in automobiles


Container :

The container is made up of acid resistance hard rubber or plastic. It is divided into compartment . Each compartment form a cell of 2v. At bottom of container bridge are provided form space for sediment collection. This avoid danger of shock circuit.

Plate :

There are two type of battery plate positive and negative.Each plate is made up of frame or rigid of an alloy of Lead and Antimony. The function of grid to hold active material and carry current. Active material in positive plate is Red led (Pb3O4) and in negative plate it is Litharge (PbO) . The negative plate group contain one plate more than positive plate group.

Lead Acid Battery- Construction and working
Lead Acid Battery- Construction and working

 Separator :

To avoid direct contact and thus short circuiting of positive and negative plate a thin sheet of some non conducting material inserted between them called Saperator.

Cell Cover :

The are moulded from hard rubber each cell cover contain hole for positive and negative plate , vent and filler opening. Vents are provided to escape gas.
Electrolyte :
After assembling completely battery filled with electrolyte. It is solution of Sulphuric Acid (H2So4) contain approximately one part of sulphuric acid and two part of water by volume.


The potential difference between two metals, which are immersed in an electrolyte is called cell voltage. A battery converts chemical energy of metal submerged in electrolyte into electrical energy by means of electrochemical oxidation-reduction process.

Discharging :

working of battery chemical reaction
working of battery

When battery terminals are connected to an external load the sulphate ions in the electrolyte combined with positive and negative plate forming lead sulphate and electrical energy is released. Oxygen in active material of positive plate combines with hydrogen from sulphuric acid to form water which reduce the concentration of the acid in electrolyte. As discharge is continuous , the electrolyte become weaker. Therefore the voltage become lower as concentration of acid reduce. Eventually the battery losses its power of delivering electricity at an impressive intensity of voltage and it is said to be discharged.

Chemical Reaction :

working of battery chemical reaction
Chemical Reaction of battery charging and discharging

Charging :

The active chemical can be restored to the charged state by passing current in opposite direction. This is said to be charge condition of battery.

Charging Reaction
Charging Reaction

Article by:
Vrushabh Dhatrak 
K B P Poly Kopergaon

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