The United States Navy has flown Sealed Lead-Acid Batteries (SLA) for approximately 15 years. The first SLA aircraft batteries were cylindrical cell design and evolved to a prismatic design to save weight, volume, and to increase rate capability. This paper discusses the evolution of the SLA aircraft battery designs, present SLA battery performance, and battery size available along with their aircraft applications (both military & commercial). The paper provides some of the reliability data from present applications. Finally, the paper discusses future evolution of the SLA technology required to improve performance and to remain the technology of choice over other sealed aircraft battery designs.