Sun Xtender® Deep Cycle AGM Batteries for renewable energy storage are manufactured in the USA by Concorde Battery Corporation and are built to the same demanding standards crucial to supporting the aircraft industry. To facilitate maximum conductivity & charge acceptance Sun Xtender® batteries are constructed with copper alloy corrosion free terminals & robust intercell connections. Endurance and optimal float life are achieved through plates thicker than the industry standard. Sun Xtender® Batteries' AGM maintenance free design is an ideal solution for off grid and grid tied systems.