Class 4 (4th Engineer) MET 📅 Sep 2024

Exam Question

A 24V emergency battery is to be charged from the 11OV 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

### **Objective**
To determine the required range of a variable resistor used to control the charging of a 24V emergency battery bank from a 110V DC ship's main supply.
### **1. Principle of Battery Charging**
When charging a battery, an external DC source with a voltage (Vs) higher than the battery's back electromotive force (Eb) is applied. The potential difference (Vs - Eb) drives the charging current (I) through the total resistance of the circuit.

Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.

View plans Browse library

← Browse more questions

Prepare on Android — MeoMock on Google Play