Question 1
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1. (a) A malfunctioning lead-acid battery is taken to an Auto Electrical Works (AEW) workshop for possible servicing and checks.
Complete Table 1 with:
(i) three tests likely to be carried out;
(ii) one instrument required for each test I n 1(a)(i).
Table 1
S/NType of test
Instrument
1.
2.
3.
(iii) State five safety precautions that should be taken when charging the battery.
(b) Fig. 1 is an arrangement of batteries.
Determine the total:
(i) capacity of the battery;
(ii) voltage the arrangement can supply.
Observation
The expected answers were;
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(a) Table 1
S/N(i) Type of test
(ii) Instrument
1.
Specific gravity test
Hydrometer
2.
Cell voltage/terminal voltage/voltage test
High rate discharge tester/multimeter
3.
Polarity test
Multimeter
4.
Float/ripple current test
Ammeter
5.
Temperature
Thermometer
6.
Battery capacity test
High rate discharge tester
7.
All forms of tests
Battery analyzer
(iii) Safety precautions that should be taken when charging the battery- safety/personal protective equipment such as goggles, hand gloves etc.
- Avoid flame/sparks that could ignite the hydrogen gas produced by the battery which can cause explosion.
- Always turn off the battery charger before connecting or disconnecting the leads.
- Use battery carriers to lift at opposite corners of the base when carrying the battery.
- Ensure good ventilation of the charging room.
- Do not attempt to charge/load-test if it is a maintenance-free battery with insufficient electrolyte.
- Disconnect the negative battery cable if the battery is to remain in the vehicle during charging.
- Ensure the ignition switch is off before connecting or turning the charger on.
- Use proper adaptors to connect charger leads to side terminal batteries.
- Slowly increase the charge rate when turning the charger on, turn the charger off if gassing/spillage occurs.
- Ensure that steady current is supplied to the battery.
- Avoid the supply of excessive current to the battery to prevent swelling.
(b) (i) Total capacity = 10AH
(ii) Total voltage = 6V + 6V =12VMajority of the candidates that attempted Question 1 responded well to 1(a) but many of the candidates did not understand how to calculate the total capacity and total voltage of batteries connected in series. They were required to understand that the total capacity of identical batteries connected in series is the same as that of individual batteries while the total voltage supply is the sum of their voltages.