Page 79 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Comparison : Lead acid cell and Edison cell
(The relative strong and weak points of the two cells have been summarized below)

S.No Particulars Lead-acid cel Edison Cell
1 Positive plate PbO, Lead Peroxide Nickel hydroxide Ni(OH) or Nickel Oxide (NiO )
4
2
2 Negative plate Sponge Lead Iron

3 Electrolyte Diluted H2SO4 KOH

4 Average emf 2.1 V/Cell 1.2 V/Cell

5 Internal Resistance Comparatively low Comparatively higher resistance
6 Efficiency : amp-hour 90-95% Nearly 80%
watt-hour 72-80% About 60%

7 Cost Comparatively less than Almost twice that of Pb-acid cell (Easy
alkaline cell maintenance)

8 Life Gives nearly 1250 Five years atleast
charges and discharges
9 Strength Needs much care and Robust, mechanically strong, can withstand
maintenance. Sulphation vibration, light, unlimited rates of charge and
occurs often due to discharge. Can be left discharged, free from
incomplete charge or corrosive liquids and fumes.
discharge

Applications
Due to their high mechanical strength, lightness and free from acid fumes they have been found to be very
satisfactory for the following applications
• Traction purpose

• Mine locomotives
• Submarines
• Industrial trucks
• Aero planes

Similarity of operation NI-FE &NI-CD
• The electrolyte is same for nickel-iron and nickel-cadmium cell .ie potassium hydroxide(KOH)
• When the cell is discharged the positive plate is converted in to Ni(OH)2
The specific gravity of electrolyte is remain unchanged during charge or discharge
Nickel cadmium cell

Nickel cadmium cell is similar to nickel iron nickel hydroxide Ni(OH)2 for the positive electrode. Cadmium Cd as
the negative electrode. Potassium hydroxide (KOH)electrolyte
NI-CD Cell operation
• It consist of cadmium anode and a metal grid containing a paste of NiOH2 acting as a cathode.

• The electrolyte is KOH (potassium hydroxide)
Working (discharging)
• When the Ni-Cad battery operates, at the anode cadmium is oxidized to Cd2+ ions and insoluble Cd(OH)2
is formed.
• It produces about 1.4V

66

CITS : Power - Electrician & Wireman - Lesson 13-19