The vehicle charging system should be used to charge a completely discharged battery. The negative battery cable may need to be disconnected when charging a battery in the vehicle. Who is right?

• A. A only
• B. B only
• C. Both A and B
• D. Neither

Answer: (B)

Charging a completely dead battery cannot be reliably or safely done using the vehicle’s own charging system. The alternator is designed to top up a battery that already has some charge and is being driven by the engine; if the battery is fully discharged, there’s little or no voltage to regulate, so the alternator won’t effectively charge it and starting the engine may not be possible. The safer approach is to use an external charger (or a jump-start from another vehicle) to bring the battery up to a usable level, then let the alternator finish charging once the engine is running.

When charging a battery in the vehicle, it’s common practice to disconnect the negative cable to isolate the battery from the rest of the electrical system. This helps prevent backfeeding into other circuits, reduces the risk of sparks or damage to sensitive electronics, and makes the charging process safer. After the battery is charged, reattach the negative cable and verify proper operation.