Advanced batteries for electrically powered underwater vehicles

Abstract

Electric propulsion systems have numerous benefits for unmanned, untethered submersibles. However, the low energy density and low specific energy of conventional batteries have made electric systems large and heavy. Four advanced battery technologies, currently under development at Gould, are substantially smaller and lighter than conventional batteries having equivalent power and energy capabilities. Rechargeable high temperature lithium alloy-iron sulfide cells which demonstrate 2.5 to 3 times the specific energy of advanced lead-acid batteries have been built and tested. More than 500 deep discharge (100% DOD) cycles were obtained before cell failure. Physical and electrical abuse safety tests on this cell design resulted in no venting or other hazardous conditions. Battery systems of 7.2 kWh capacity (200 Ah at 36V) have been built and are being life cycle tested. Cells have achieved specific energy of 110 Wh/kg (220 Wh/liter) and battery systems, based on these cells, are predicted to achieve 85 Wh/kg (100 Wh/liter). p>Lithium-oxygen primary batteries are being developed for long endurance (high total energy) applications where electrical recharge is not required. The lithium-oxygen battery consumes lithium metal and stored oxygen (pressurized gas or cryogenic liquid) to produce electrical power. The battery uses a flowing alkaline electrolyte to remove waste heat and reaction products. This battery system is projected to have a specific energy of over 3,000 Wh/kg of reactants. Aluminum-silver primary oxide batteries (which also use a flowing electrolyte) have been developed for underwater propulsion systems which require high power as well as high specific energy. This seawater activated battery has application as an emergency or auxiliary power source on board unmanned submersibles. Magnesium-seawater primary battery chemistry has been developed for low power-long endurance applications where simplicity and low cost are important. The battery consumes magnesium alloy and dissolved oxygen from the seawater. The specific energy of magnesium consumed is expected to be 1500 to 2000 Wh/kg.