Eaton Wheelock's sealed lead acid batteries are leak proof and maintenance free. They are based on a unique efficient oxygen recombination technology. Oxygen evolves from the positive plates and diffuses through the micro porous glass fibers to the negative plates where it is changed back to water by recombination reaction. This process eliminates the need for water replacement.All battery models are designed per NFPA 72 (2002) Section (6.9.4.5) for use with engine driven generators, local central station or proprietary systems and auxiliary or remote station systems.The (BACT-R) enclosure is constructed of steel and its' door hinges fold downward for easy loading of the batteries. It also comes with a lockable door that is keyed like the SAFEPATH control panel.