Which systems run off of the "Battery" bus?

The systems powered by the "Battery" bus typically include essential flight and operational indicators that require a consistent power supply regardless of the aircraft's engine status. These indicators, such as the clock, Hobbs meter (which tracks engine time), tachometer (measuring engine RPM), and often the heater meter, are crucial for the pilot’s operation and monitoring of the aircraft even when the engines are not running.

The battery bus is designed to provide power to these critical systems to ensure that fundamental operational data is available at all times, especially during pre-flight checks or in case of an engine failure.

Other systems, such as navigational equipment and radios, might rely on different power buses, often linked to the alternators or generators that kick in when the engines are operational, as they typically consume more power. Lighting systems often have dedicated circuits rather than relying on the battery bus.