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Misleading Results Using IEEE Battery Testing Procedures

Jim McDowall

There is a fundamental conflict between the IEEE sizing method and IEEE testing recommendations. For an application in which the end of useful battery life is set at 80% of rated capacity, the sizing method defines this point using 80% of published current for 100% of the time, while the testing procedure defmes it using 100% of the current for 80% of the time. The testing calculation method is flawed, in that it ignores changes in battery efficiency at different discharge times. While tests of long duration are relatively unaffected, this inconsistency can have pronounced effects on high-rate testing. Batteries can appear to fail prematurely, often after just a few years in service. This paper analyzes the problem and outlines what the IEEE battery standards committee is doing to address the issue.

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