The feasibility for a portable rechargeable thermal battery, RTB, was demonstrated. A number of applications for ARMY field training, eg. soldier systems, require increased power, 250 W, for extended periods, 2-8 h and need to be man-packable.about 10 lbs. A rechargeable battery is sought to reduce ARMY cost and disposal requirements. Safety and durability are obvious requirements for a battery that has a lot of personal interaction. An advanced molten-salt battery chemistry:LiAl/FeS{sub}2-CuFeS{sub}2 with LiI additive shows enhanced high rate capability. Power is double that of the common LiAl/FeS{sub}2-CoS{sub}2 chemistry. The reengineering of the Li/FeS{sub}2 cells for increased specific energy was accomplished by a series of cells with increasing cell capacity: 25, 30, 38, 45 Ah. Test results reflected the ability to achieve 80-90% capacity utilization with thicker (high capacity) electrodes. The Li/FeS{sub}2 cell, intrinsically durable, requires no instrumentation toavoid over-discharge. and poses no safety concern in overcharge or over-discharge. The performance of 4-cell bipolar Li/FeS{sub}2 batteries further demonstrated the feasibility of the rechargeable thermal battery to fill a unique niche. The projectedperformance of a 10 cell, 38Ah, 640. Wh bipolar battery is capable of 250 W draw for 2-6 hours. Rigorous full discharge capacity testing under constant power conditions of 62.5, 125, 187.5 and 250 W for the 10 cell battery demonstrates specific energy ofabout 140 Wh/kg.,Surprisingly, the elevated temperature of RTB, generally seen as a drawback, becomes the key to forming/maintaining a vacuum insulated housing. We have designed a battery with a 3 Watt heat loss which balances the requirements of high specific energy andstill goes days between recharge. The insulated casing makes the battery immune to ambient hot/cold conditions.
展开▼
