What is the main function of the Battery Bus?

The main function of the Battery Bus is to provide DC power for the battery or GPU (Ground Power Unit). This is essential for powering critical systems when the aircraft’s engines are not running or when external power is not available. The Battery Bus acts as a centralized distribution point for electricity generated by the aircraft's battery, ensuring that vital systems have the necessary power supply to function correctly during ground operations or in-flight scenarios when engine power may be temporarily unavailable.

Understanding this role is vital for managing electrical failures and ensuring the aircraft's systems remain operational. Other options may relate to power distribution in the aircraft but do not specifically describe the primary role of the Battery Bus.