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Modules made by Yuasa Corporation were tested for cycle life in dynamic stress tests (DST), power capabilities, and thermal performance. The modules completed 330-350 life cycles. The thermal performance experiments (over the temperature range of • 10 to +50°C) show that DST and C/3 capacities and power capabilities are reduced by more than 12% at • 10 and at +50°C. In life-cycling studies, changing the charging algorithm from a temperature-compensated return to a simple 105% return decreased the capacity and power fade rates by almost a factor of two.

Advanced battery technology evaluations are performed under simulated electric-vehicle operating conditions at the Analysis & Diagnostic Laboratory (ADL) of Argonne National Laboratory. The ADL results provide insight into those factors that limit battery performance and life. The ADL facilities include a test laboratory to conduct battery experimental evaluations under simulated application conditions and a post-test analysis laboratory to determine, in a protected atmosphere if needed, component compositional changes and failure mechanisms. This paper summarizes the performance characterizations and life evaluations conducted during 1991 - 1992 on both single cells and multi-cell modules that encompass eight battery technologies [Na/S, Li/MS (M=metal), Ni/MH, Ni/Cd, Ni/Zn, Ni/Fe, Zn/Br, and Pb-acid]. These evaluations were performed for the Department of Energy, Office of Transportation Technologies, Electric and Hybrid Propulsion Division, and the Electric Power Research Institute.

During 1988, battery technology evaluations were performed for the Department of Energy and Electric Power Research Institute at the Argonne Analysis & Diagnostic Laboratory. Cells and multicell modules from four developers were examined to determine their performance and life characteristics for electric vehicle propulsion applications. The results provide an interim measure of the progress being made in battery R&D programs, a comparison of battery technologies, and a source of basic data for modeling and continuing R&D. This paper summarizes the performance and life characterizations of twelve single cells and six 3- to 24-cell modules that encompass four technologies (Na/S, Ni/Fe, lead-acid, and Fe/Air).

Over the operational life of a battery, the voltage characteristics of its individual cells become mismatched due to differences in self-discharge rates, individual charge efficiency, active material retention, etc. As these cell differences increase, excessive overcharging, operating temperatures, and/or electrolyte consumption result. In a series of tests performed on 6-volt, lead-acid modules, the degree of cell mismatch and the response of the modules to various charge methods were examined. The results show that after about 150 deep-discharge cycles, each module contained at least one cell whose full-charge voltage level was reduced. Prior to any decline in module capacity, cell voltage differences of more than 0.4 V were measured during charge. It was also observed that the application of a fixed battery voltage for charge control eventually caused excessive overcharging, elevated temperatures, and/or an extreme overvoltage condition on individual cells.

Chopper-type controllers commonly used in electric vehicle propulsion systems impose pulsed-current discharge conditions on the battery that influence both its internal power losses and available energy. In order to optimize propulsion system design, those discharge parameters that affect battery performance must be understood and characterized. In a series of tests performed on Exide EV-106 and EE-IV lead-acid traction batteries, a range of operating values were examined for current pulse frequency, average current discharge rate and pulse-to-average current level ratio. For each test, one parameter was selected as the variable while the other two parameters were maintained at fixed levels. Constant-current discharges were periodically performed during each test to relate battery performance for equivalent pulsed and constant current discharge conditions.