An articulated haul truck has a problem with its charging system. The voltmeter on the dashboard reads 26 V while the engine is running at operating speed. However, a battery specific gravity test shows one battery significantly lower than the others. What is the most likely issue?

Question: An articulated haul truck has a problem with its charging system. The voltmeter on the dashboard reads 26 V while the engine is running at operating speed. However, a battery specific gravity test shows one battery significantly lower than the others. What is the most likely issue?

Answer options:

• The alternator is overcharging the battery bank.
• The alternator output voltage regulator is faulty. ✅ A shorted cell within one of the batteries in the system.
• The main charging cable from the alternator is corroded.

Correct answer: A shorted cell within one of the batteries in the system.

Explanation: If the system voltage reads a healthy 26 V and one battery shows significantly lower specific gravity, it points to an issue with that specific battery, most likely a shorted cell. A shorted cell reduces the effective voltage of that battery, causing the remaining healthy batteries to accept most of the charge, leading to an imbalance. The alternator and regulator appear to be functioning correctly by maintaining 26 V system voltage. A corroded charging cable would affect the charging of all batteries, leading to a consistently lower system voltage.