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The Air Force Research Laboratory, Energy Storage and Thermal Sciences Branch conducted performance tests of 22 Ah nickel-metal hydride (Ni-MH) cell packs containing four prismatic sealed design cells over the operational temperature range for a modern fighter aircraft at the C/2, C and 2C rates. Capacity tests indicated satisfactory performance at the C/2 and C rates down to -30 °C and at the 2C rate down to -20 °C. Self discharge tests at elevated temperatures up to +60 °C were also conducted. Test results will be presented and implications for further development of an environmental main aircraft battery will be discussed.

As part of the DoD/NASA Lithium-Ion and More-Electric Aircraft (MEA) development programs, in-house life-testing and performance characterization of lithium-ion batteries of sizes 1-20 amp-hours (Ah) were performed. Using AC impedance spectroscopy, the impedance behavior of lithium-ion cells with respect to temperature, cycle number, electrode, and state-of-charge was determined. Cell impedance is dominated by the positive (cathode) electrode, increases linearly with cycle number, and exponentially increases with decreasing temperature. From cell performance testing, we have seen the cell behavior is extremely sensitive to the ambient temperature. Preliminary battery performance results as well as AC impedance and life cycle test results are presented below.

The performance and life of lithium-ion batteries is highly dependent on factors such as temperature, charge/ discharge rate, depth-of-discharge (DOD), charge cut-off voltage, and battery design. The purpose of this on-going investigation is to characterize the state-of-the-art in lithium-ion battery performance and life as a function of some of these factors. Cycle life data on 18650 cells as well as a four cell series connected 20 Ahr lithium-ion battery (16.4 volt) is presented. External cell temperatures as a function of discharge rate and location for 20 Ahr lithium-ion cell are given. Preliminary ac impedance results for the 20 Ahr cell are also given.