Long Life Thermal Battery for Sonobuoy
Final rept. 1 Jun-30 Nov 98
INVENTEK CORP NEW LENOX IL
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The Phase 1 work provided a proof of concept for a long life thermal battery. Life of the state of the art thermal battery is extended from 2.5 to 6.0 hours for sonobuoy application to meet advanced development objectives. As proposed, long life is accomplished by significantly improved heat retention using vacuummultifoil insulation rather than Microtherm insulation. First, the work evaluated a battery mockup with an actual battery case and its Microtherm insulation components. Its cooling profile simulated the actual batterys time at operating temperature. This battery mockup, using the same header, was then placed into the vacuummultifoil VIM insulated battery case. The battery mockup within the VIM insulation has its cooling profile extended more than two fold temperature decrease per hour for the VIM insulation was about 40 of the conventional Microtherm insulation. Also, as calculated by our detailed spreadsheet model, 75 of the heat loss in the VIM case mockup came from the header. The SBIR gave proof of concept to other advanced battery features. 1 A ceramic fiber separator exhibited improved handling properties and also gave comparable cell performance to MgO powder. The fiber separator may reduce cost of manufacturing the battery. 2 An alternative cell chemistry with FeS2-CuFeS2 cathode showed 50 increased peak power. Cell tests were conducted at 480 deg C to provide a comparison with a baseline CoS2LiSi cell design using 0.9Acm2, 10 sec power pulses over a 6 h period. The results show the feasibility of a thermal battery with a 6 h life, as required of the battery for an advanced sonobuoy. Also, a live thermal battery test, although of a different size, exhibited more than a doubling of operating life due to the superior heat retention afforded by VIM insulation.
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