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Describe the construction of a lead acid cell and explain the process of charging and discharging of the cell

Describe the construction of a lead acid cell and explain the process of charging and discharging of the cell.

Answers

gregory
Construction of lead acid cell and process of charging and discharging of cell:
A lead acid type batteries are known as secondary battery or cell, which can be
charged for reuse. This cell has following components:
- Anode or positive plate: It consist lead peroxide deposited on grid frame of
antimony lead alloy.
- Cathode or positive plate: It consists of porous-spongy lead pasted on grid frame.
- Electrolyte : Sulphuric acid is an electrolyte. It is prepared by diluting pure
H2SO4 & specific gravity of fully charged cell is 1.23 at 270C.
- Separator : These are thin porous sheet suspended between positive and negative
electrode to prevent short circuit.
- Vent plugs: Its purpose is to allow/escape of gases but prevent escape of
electrolyte.
- Battery terminals : These are made of nickel plated copper alloy.
- Container : It contains all plates, electrolyte, separators, vent plug, cell connectors
and battery terminals. It is made of hard rubber.
- Cell connectors : These are used to connect a number of cells of same type (either
negative or positive) in series so as to provide required voltage.
Charging process:
Connect dc supply to electrodes with corresponding polarity. The direction of current
now opposite to that in discharging process. The current flow from external dc source to
positive electrode to negative electrode through the electrolyte and back to the source.
This process results in rise in cell voltage 2 or 2.1 volts and specific gravity 1.230
The reaction taking on electrodes are :
At anode : PbSO4 + SO4 + H2 O ® PbO2 +2 H2SO4
At Cathode: PbSO4 + H2 ® Pb + H2SO4
Discharging process:
When cell is fully charged anode is PbO2 and cathode is Pb. An external load is
connected to electrodes of cell, therefore, an electric current flows in load. The process is
known as discharging. A fully discharge cell has a voltage 1.8 volts and specific gravity
1.180.
The reaction-taking places at electrodes are
At anode : PbO2 + H2 + H2SO4 - PbSO4 + H2O
At Cathode: Pb + SO4- PbSO4
gregorymasila answered the question on February 22, 2018 at 16:28

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