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The objective of this study was to assess the long-term capability and impact of a rapid, in-situ impedance measurement technique known as Harmonic Compensated Synchronous Detection. This technique consists of a sum-of-sines excitation signal that includes a targeted selection of frequencies and only requires one period of the lowest frequency. For a given frequency range of 0.1 Hz to approximately 2 kHz, the measurement duration would only be ten seconds. The battery response is captured and synchronously detected for impedance spectra measurements. This technique was compared to laboratory-based performance degradation measurements using commercially available lithium-ion cells. The cells were aged for 150,000 cycles at accelerated rates using temperatures of 40 and 50°C. Every 30,000 cycles, cycle-life testing was interrupted to gauge degradation at the reference temperature of 30°C.

Novel testing procedures and analytical methodologies to assess the performance of hybrid electric vehicle batteries have been developed. Tests include both characterization and cycle life and/or calendar life, and have been designed for both Power Assist and Dual Mode applications. Analytical procedures include a battery scaling methodology, the calculation of pulse resistance, pulse power, available energy, and differential capacity, and the modeling of calendar- and cycle-life data. Representative performance data and examples of the application of the analytical methodologies including resistance growth, power fade, and cycle- and calendar-life modeling for hybrid electric vehicle batteries are presented.

Advanced battery safety is of concern for the successful commercialization of these technologies. The USABC (United States Advanced Battery Consortium) and PNGV (Partnership for a New Generation of Vehicles) are developing high power battery systems for use in electric and hybrid/electric vehicle applications. Part of the objectives of these programs is to establish and verify testing procedures regarding the safety and abuse resistance of particular batteries or battery technologies. This paper will discuss the status of abuse testing procedures that have been developed for battery systems. The goal of these tests is to determine the extent to which defined abuse conditions contribute to venting, rupture, release of hazardous substances, fire, smoke or uncontrolled energy releases. Areas of abuse testing that have been identified are (1) mechanical, (2) electrical, and (3) thermal.