What is the minimum battery voltage required to start the APU?

The minimum battery voltage required to start the APU is 22 volts. This specification ensures that the APU receives adequate power to initiate the start sequence effectively. Starting an APU involves overcoming certain mechanical resistance and powering up components such as the starter motor and fuel system; thus, sufficient voltage is critical for reliability during this process.

Operating below this voltage may result in insufficient power to initiate the start sequence, potentially leading to an unsuccessful start or damage to the APU. Therefore, the requirement of 22 volts aligns with the operational parameters set by the manufacturer to promote optimal performance and safety of the aircraft systems.