What is the function of the main bus battery?

The main bus battery serves a critical role in the overall operation of a bus. It provides the power necessary to start the engine, which is essential for the bus to function. Additionally, the battery supplies electricity to run various electrical components within the vehicle when the engine is not running. This includes systems essential for vehicle operation and safety, such as lights, communication devices, and other electronic systems.

While air conditioning, braking assistance, and the operation of wipers and lights rely on electrical power, they are functions that may not solely depend on the main bus battery or may have additional sources of power available, which distinguishes their reliance from the primary role of the main bus battery itself. The correct answer underscores the battery's fundamental responsibility in starting the bus and supporting essential electrical systems.