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Class 4 (4th Engineer) MET 📅 Aug 2025

Exam Question

(a) Describe an alkaline battery cell, listing the materials used in its manufacture. (6)

(b) With reference to alkaline batteries used on ships, state each of the following: (10)

(i) significance of the relative density reading of the electrolyte;

(ii) when the electrolyte would normally be renewed;

(iii) reasons why the voltage reading of this type of battery is not necessarily indicative of its condition;

(iv) the normal temperature range and safe temperature limit of battery;

(v) effects of high and low temperature. 

Reference Answer

### (a) Alkaline Battery Cell Description and Materials
An alkaline battery, specifically the Nickel-Iron (Ni-Fe or Edison Cell) or Nickel-Cadmium (Ni-Cd) type commonly used in marine applications, is a secondary (rechargeable) cell known for its extreme robustness, long service life, and ability to withstand electrical and mechanical abuse.
**Principle of Operation:**
The cell operates on the principle of reversible electrochemical reactions. During discharge, the active material in the positive plates is reduced, and the active material in the negative plates is oxidized. During charging, this process is reversed. Unlike lead-acid batteries, the electrolyte (Potassium Hydroxide) acts primarily as an ion carrier and its specific gravity does not change significantly with the state of charge.

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