Comparing different vibration tests proposed for li-ion batteries with vibration measurement in an electric vehicle

Li-ion batteries are the most popular type of batteries in electric, EV, and hybrid vehicles, HV. During their life time the batteries will be subjected to vibrations and therefore vibration testing is demanded by several standards. Testing on different size levels of the batteries, i.e. cell, module or pack, are proposed. Depending on the standard random vibration tests or tests with sinusoidal excitation are required. To compare these standards with the measurements, Fatigue Damage Spectrum, FDS, and Shock Response Spectrum, SRS, have been used. The FDS is a tool to analyze and compare different types of vibration tests and vibration measurements with respect to the fatigue damage that the vibration will cause on a mechanic structure. The SRS is used to estimate the risk for functional disturbances in electric equipment subjected to shock and vibrations. The comparison shows that the FDS and SRS for different vibration tests proposed for li-ion batteries vary strongly. Both levels and frequency ranges differ. One of the compared standards prescribes testing only in the vertical direction. The measurement done in this study was done during rather hard driving on a test track, this means high but not unrealistic measured acceleration responses. For one of the measured responses, the risk for fatigue during service could be higher than the risk at the tests. The low frequency content of a test can be important as the measurements show higher low frequency content than in many of the standardized tests. But even the high frequency content of the test must be considered as batteries normally are equipped with a large number of small electrical devices with high critical frequencies. Only one of the standards requires a separate test of such devices.