Class 4 (4th Engineer) MET 📅 Nov 2023

Exam Question

A 24V emergency battery is to be charged from the 110V ship's mains when the e.m.f. per cell has fallen to a minimum value of 1.8V. The battery consists of 12 cells in series, has a capacity of 100 Ahr at a 10 hr rate and the internal resistance is 0.03Ω/cell. If charging continues until the voltage per cell rises to 2.2V, find the value of the variable resistor needed to control the charging. The charging current can be assumed to be equal to the maximum allowable discharge current. (16)

Reference Answer

The charging of a ship's emergency battery from the main supply requires careful control to prevent overcurrent, which can damage the battery and the charging circuit. A series variable resistor is employed for this purpose, allowing the charging current to be regulated as the battery's electromotive force (e.m.f.) changes during the charging cycle.
### 1. Problem Statement
To determine the specific value of the variable resistor required to control the charging current for a 24V emergency battery system from a 110V ship's mains supply.
### 2. Given Data

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