Validation of Vibration Test for Lithium-ion Battery Pack in Electric Vehicles 2015-01-1195
To verify the appropriateness of the vibration test conditions of ISO 12405, we performed tailoring to derive power spectrum densities and test durations as vibration test conditions. Vehicles used for tailoring included two electric vehicles and one plug-in hybrid electric vehicle. Those vehicles were equipped with accelerometers and were run on seven different road types at different speeds while data on the acceleration of the battery packs were recorded.
The power spectrum densities for three axes that were derived from the obtained acceleration data were similar in form to the power spectrum densities of ISO 12405, and almost the same root mean square accelerations were obtained, confirming that they are appropriate.
However, both experiments and theory suggest that the test duration for the Z-axis exceeds those of the X- and Y-axes. Therefore, the test durations for the X- and Y-axes in ISO 12405, where the test durations for the three axes are 21 hours, may not reflect the actual state of running. Test duration depends on the root mean square acceleration of each sub-scenario and on the running time assumed for each sub-scenario, and the root mean square acceleration tends to be higher in the vertical direction than in the horizontal directions. As an example of calculating the test duration, we supposed the running distance of each sub-scenario assuming that ISO 12405 specifies the test duration so that the test durations for the X- and Y-axes are consistent with that for the Z-axis, which is the longest. We consider that 6 hours for the X-axis and 4 hours for the Y-axis are test durations that reflect the actual running state more accurately.