Study on comprehensive performance of Ni-MH power battery used in HEV at different temperatures

This study carries a comprehensive investigation on the influences of the key environmental and operating parameters on SOC and cycling life of the Ni-MH battery. The Ni-MH cells were tested through loading the actual road spectrum at different temperatures (25/35/45°C). Other parameters of SOC fluctuation and currents are set to be 10% and 15.5A by average, respectively. Tests have been performed to obtain the OCV (open circuit voltage)~SOC curves at different temperatures under the 1-C rate of charging/discharging. The investigation results show that the capacity decay compared to initial capacity is increased by a slight 2.46% at 45°C, demonstrating an excellent cycling performance of the Ni-MH battery. Additionally, the battery polarization effect is found to be correlated to the charging and discharging processes and temperature. In summary, this study presents a comprehensive factor analysis needed to achieve a reliable SOC estimate for the Ni-MH based HEV.