What is a consequence of a low battery voltage affecting the APU?

A low battery voltage indeed impacts the Auxiliary Power Unit (APU) by hindering its ability to start effectively. The APU relies on adequate electrical power to initiate the starting sequence of its engine, similar to how a vehicle's starter motor operates. If the battery voltage is low, the APU may not receive enough power to engage the starter motor fully, which can result in a failed start or a prolonged cranking period that could lead to further complications, such as overheating of the starter components.

When the battery voltage is at an optimal level, it provides sufficient power to allow the APU to start quickly and efficiently, enabling it to perform its intended functions, such as supplying electrical power and pneumatic pressure for engine start or environmental control systems. Thus, low battery voltage directly affects the reliability and functionality of the APU, making it a significant concern for the operation of the aircraft.