Selecting the correct chemistry is vital for performance and longevity. Nickel-Cadmium (Ni-Cd) is traditional and robust in high temperatures, but Nickel-Metal Hydride (Ni-MH) offers higher energy density and is more environmentally friendly. For modern, high-efficiency LED systems, Lithium Iron Phosphate (LiFePO4) is increasingly preferred due to its longer cycle life (up to 2000+ cycles), lightweight profile, and superior thermal stability. Always match the battery chemistry to the specific charging circuit of your emergency light fixtures.