What does the Backup Battery Button do on the overhead panel?

What does the Backup Battery Button do on the overhead panel?

• A. Disengages the backup battery from the bus
• B. Controls the backup battery contactor, allowing charging of backup battery when closed
• C. Turns on the main generators
• D. Switches the battery to hot bus

Answer: (B)

The button’s job is to control the backup battery contactor. When pressed, it closes the contactor circuit so the backup battery is connected to the charging path and can be charged by the aircraft’s electrical system. When released, the contactor opens, isolating the backup battery from the charging source and preventing unnecessary discharge. This action keeps the backup battery ready for use if power is lost, without turning on the main generators or switching the battery directly to the hot bus.

The button’s job is to control the backup battery contactor. When pressed, it closes the contactor circuit so the backup battery is connected to the charging path and can be charged by the aircraft’s electrical system. When released, the contactor opens, isolating the backup battery from the charging source and preventing unnecessary discharge. This action keeps the backup battery ready for use if power is lost, without turning on the main generators or switching the battery directly to the hot bus.