The DataShield AT800 is a UPS system that requires a 12V 26Ah AGM replacement battery. The compatible Universal Power Group replacement is the UPG UB12260 12V 26AH T3 AGM Battery (UB12260), a 12V 26Ah AGM sealed lead-acid battery. It uses T3 terminals. This is a direct drop-in replacement for the DataShield AT800 requiring no modification to the device.