Comparison of Various cells Batteries

Batteries

           A cell also known as Storage cell.

• ·         A cell is a source of D.C in which Chemical Energy is converted into  Electrical Energy.
• ·         A group of such cells either connected in either series or parallel or series – parallel is known as Battery.
• ·         This process is called Electro Chemical action. A cell consists of two dissimilar metal plates ( Say Copper and Zinc) immersed in an electrolyte .

• ·         The chemical action in the cell causes copper plate to become Positively charged and Zinc plate Negatively charged.
• ·         If plates of Zinc and lead are placed in a solution of H₂SO_4, the emf developed  is about 0.5 Volts . Zinc and Copper in H₂SO₄ about 1.1 Volts.
• ·         The E.M.F of a cell does not depend upon the size and spacing between the plates.
• ·         With the increase in the size of the plates the capacity of the cell increases i.e the cell will deliver current for the longer period.

Particulars	Lead acid Type	Nickel Iron Type	Nickel Cadmium Type
Active material on positive plates when fully charged	Lead peroxide	Nickel Hydroxide	Nickel Hydroxide
Active material on negative plates when fully charged	Spongy lead	Iron	Cadmium
Container used	Glass or Ebonite	Steel	Steel
Electrolyte	Dilute sulphuric acid	Potassium Hydroxide	Potassium Hydroxide
Activity of electrolyte	Takes part in reactions	Does not take part in reaction	Does not take part in reaction
Variation of Sp. Gr. of electrolyte during charge and discharge	Varies from charge to discharge between 1.21-1.15	Remains  constant at 1.22	Remains constant at 1.17
Volume of electrolyte required	More	Less	Less
Size of the battery	Large	Small	small
Emf/cell on full charge	2.2 volts	1.48 volts	1.62 volts
Emf on discharge (Recharging is required)	1.8volts	1.15 volts	1.33 volts
Internal resistance	About 0.02W	About 0.1 W	About 0.05 W
Capacity	10hrs discharge	5hrs discharge	5hrs discharge
Charging & discharging	Lower rate of charging is used.  It cannot with stand higher rate of charging & discharging	Can withstand  higher rate of charging  & discharging	Can withstand higher rates of charging & discharging
Ability to short circuits	When shorted the life of battery falls to a much lower value	Short circuits do not affect the life	Short circuits do not affect the life
Life	About 12000 charge & discharge cycles	About 5 years	About 5 years
Cost	Lesser	High	high
Weight	More	Lighter	Lighter
Mechanical strength	Less	More	More
Maintenance & care	Requires frequent maintenance	Requires less care	Requires less care
A.H efficiency	About 95%	About 80%	About 80%
W.H efficiency	About 75%	About 60%	About 60%
Applications	In laboratories, automobiles power stations , substations, trains etc.	For traction mines, emergency lights, aviation etc.	For traction mines and aviation etc.,