Electro Energy Inc.'s (EEI's) patented bipolar nickel-metal-hydride battery design, based on flat wafer cells, has resulted in high power and energy densities. This design approach leads to increased capacity at a reduced weight and volume, when compared to other rechargeable batteries and energy storage devices. These advantages make the bipolar NiMH a logical choice for Army Silent Watch applications, where it is essential to maximize energy and minimize weight and volume. Through programs with Army Cecom EEI has successfully built a high energy battery system that would replace existing lead-acid batteries and provide silent watch operation for an extended period of time. In addition, the bipolar Silent Watch battery offers reduced volume and weight over fuel cells considered for this application. EEI's internal safety/control system allows the battery to serve as a drop-in replacement for many applications requiring silent watch operation. By monitoring cell pressures and module temperatures, the individual battery packs within the modules are controlled and dropped in and out of use, resulting in safe operation and limited down time. EEI's silent watch battery module is rated at 24 V, 90 Ah, with dimensions of 6.73"×14.13"×12.25", at 110 lbs. The module is comprised of 5 parallel 24 V, 18 Ah packs, each individually controlled. Multiple modules can be connected in parallel to provide increased silent watch operation. In this paper, EEI will discuss the bipolar NiMH Silent Watch battery system design features and demonstration and test data results. It focuses on the benefits of the extensive research that has been conducted towards the development of a highly reliable, long cycle-life, man-portable power system to support the Army's electronic equipment.
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