Seawater batteries for low power, long term applications

Two different seawater cells for long term discharge (years) have been developed. One type is for deep-sea use, whereas the other cell is intended for use close to the surface where biofouling is a major problem. The energy density of a complete system with DC/DC power converter and secondary battery in a pressure-resistant casing is above 600 Wh/kg for both cells. The seawater environment and cell development are discussed. Common properties for these seawater batteries are: infinite shelf life when dry; environmentally safe (neither poisonous or flammable): only the electronics design is pressure dependent; low lifetime cost (only the anodes are expendable); high energy density: and low power density