What is one of the main uses of the main battery?

The main battery's primary role is to provide the necessary electrical power for engine start. In aircraft systems, especially during the start-up phase, the main battery delivers a significant amount of current to the starter motor, which initiates the combustion process within the aircraft's engines. This function is critical, as a successful start is a prerequisite for normal aircraft operations.

While emergency lighting, flight navigation, and passenger comfort systems rely on electrical power, these systems are typically supported by auxiliary or backup batteries and the aircraft's main generators once the engines are running. The immediate need for power during engine start highlights the main battery's importance in this specific function.