If the battery voltage does not rise during engine start or TRU operation, what fault is indicated?

If the battery voltage does not rise during engine start or TRU operation, what fault is indicated?

• A. External power issue.
• B. TRU failure.
• C. Fault in the battery charging circuit.
• D. Standby inverter fault.

Answer: (C)

Battery voltage should rise when the engine start sequence engages or when the TRU is supplying the DC bus because the charging path feeds current back into the battery. If the voltage does not rise in those situations, the charging path isn’t delivering current, pointing to a fault in the battery charging circuit. This could involve the TRU itself, a blown fuse or open in the charging line, a faulty charging relay, or wiring issues in the charging circuit. It’s not primarily an external power issue or a standby inverter fault, since the symptom specifically indicates the charging path to the battery isn’t functioning.

Battery voltage should rise when the engine start sequence engages or when the TRU is supplying the DC bus because the charging path feeds current back into the battery. If the voltage does not rise in those situations, the charging path isn’t delivering current, pointing to a fault in the battery charging circuit. This could involve the TRU itself, a blown fuse or open in the charging line, a faulty charging relay, or wiring issues in the charging circuit. It’s not primarily an external power issue or a standby inverter fault, since the symptom specifically indicates the charging path to the battery isn’t functioning.