Even with all the advances in aviation, many aircraft still use battery technology that’s over a century old. Lead acid batteries, introduced in 1899, and nickel cadmium (NiCad) batteries, which came soon after, remain widely used. However, lithium ion batteries have become a popular modern alternative. This newer battery technology offers high energy density and lower weight—two key needs in aviation. In this article, we’ll compare lead acid, NiCad, and lithium ion batteries, highlighting the unique benefits and challenges of each type.