What type of battery is the standby battery?

The standby battery in most aircraft systems is typically a 24V DC lead-acid battery. This type of battery is chosen for its reliability and capability to provide consistent power for essential systems in the event of a main power source failure. Lead-acid batteries are well-known for their robust performance, proven technology, and relatively low cost, making them a dependable choice for aviation applications.

It's important to note that while other battery types are used in various applications, they may not meet the specific requirements for standby or emergency systems in aviation. For example, lithium-ion batteries, while popular for their energy density, may not provide the same level of safety or reliability in situations where immediate power is critical. Nickel-cadmium batteries, though used in some aircraft, do not generally serve as standby batteries due to their other limitations. Gel batteries, while providing good performance, are not standard in most aircraft systems for standby power. This context underscores why the lead-acid battery remains the preferred option for standby use in aviation settings.