The United States Navy has flown valve-regulated lead-acid batteries (VRLA) for approximately 22 years. The first VRLA aircraft batteries were of a cylindrical cell design and these evolved to a prismatic design to save weight, volume, and to increase rate capability. This paper discusses the evolution of the VRLA aircraft battery designs, present VRLA battery performance, and battery size availability along with their aircraft applications (both military and commercial). The paper provides some of the reliability data from present applications. Finally, the paper discusses what future evolution of the VRLA technology is required to improve performance and to remain the technology of choice over other sealed aircraft battery designs. (C) 2004 Published by Elsevier B.V.