Why Are Lead Acid Batteries Used in Airplanes?

Lead acid batteries are common in many industries as a direct current (DC) power source for various components and devices, but their use in aviation stands out in particular as a result of the specific demands of electrical systems in such settings. Understanding why lead acid batteries are still so favored despite various other options being available requires a closer look at how they function, so read on to learn more about what factors support their use in modern aircraft.

Invented in 1859 by Gaston Planté, lead acid batteries are one of the oldest rechargeable types. Despite its age, this technology remains prevalent thanks to its simplicity, robustness, and effectiveness for varying applications. These batteries work by converting chemical energy into electrical energy through a reversible reaction, where their design consists of lead dioxide as a positive plate, lead as a negative plate, and an electrolyte solution made of sulfuric acid. When the battery discharges energy, the two plates react with the sulfuric acid, creating electricity while forming lead sulfate and water as a byproduct. When recharged, the process is reversed, restoring the lead dioxide and lead electrodes.

Lead acid batteries can be divided into two primary types: flooded and sealed. Flooded batteries, also known as wet cells, are the more traditional version, where liquid electrolyte is free to move around inside its casing. Sealed lead acid batteries, meanwhile, are designed to prevent any leakage of the electrolyte, making them more suitable for applications where vibration is prevalent. Nevertheless, both types are used in aviation depending on the specific needs of the aircraft in question.

The role of batteries in aircraft is vital, as they provide power for a variety of functions. Alongside a major role of starting engines, they power emergency systems, flight instruments, and avionics in case of an alternator failure. Lead acid batteries in particular have proven themselves as dependable under the diverse and often extreme conditions faced during flight, as they have an established track record of resilience in varying temperatures, including cold starts in icy conditions. Additionally, because of their capacity to handle short, high-power demands like those required for engine cranking, these batteries meet the operational needs of many aircraft models.

Another factor supporting the use of lead acid batteries in aviation is their relatively low upfront cost and simplicity. For instance, maintenance procedures for them have been well understood and refined over decades, ensuring a predictable and manageable upkeep schedule. Flooded lead acid batteries specifically require periodic checking of their electrolyte levels and may need to be topped off with distilled water to maintain their chemical balance, but this is a straightforward task with little to no specialized equipment needed. While sealed lead acid batteries reduce or eliminate the need for frequent water replenishment, they still follow established safety and maintenance protocols that are easily managed within the broader scope of aircraft maintenance. Given that aircraft require attention across many systems, batteries that require minimal maintenance help to streamline operations.

When comparing lead acid batteries to other types like NiCDs, there are certain trade-offs to consider. NiCD batteries offer higher energy density levels, which makes them lighter and capable of storing more energy per unit of weight. This advantage is particularly valuable in aviation, where every pound of weight saved can improve fuel efficiency and overall performance. They are also known to withstand high discharge rates without significant damage, a further benefit that has caused their adoption in various models. While NiCD variants are useful in larger commercial aircraft that require more extensive power reserves for extended operations, lead acid batteries remain a popular choice for smaller models due to their lower cost, simpler maintenance, and proven ability to provide reliable power under a variety of conditions.

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