Research on battery condition evaluation method based on big data of battery electric vehicles

In this work, the capacity attenuation characteristics, self discharge characteristics and temperature consistency of power batteries in actual on-board environments are studied. The battery condition evaluation method based on big data of new energy vehicles is explored. Results indicate that the charging capacity of power battery calculated based on the big data shows a discrete distribution, but overall shows a decreasing trend with the increase of operating mileage. When the operating mileage increases from 160,000km to 200,000km, the charging capacity within 35%~90% SOC range decreases from 66.87Ah to 64.82Ah. The daily standing time (system shutdown and not charged) of the vehicle is mainly around 2 or 10 hours. With the increase of operating mileage, the self discharge characteristic parameter slowly increases. When the operating mileage increases from 160,000km to 210,000km, the self discharge characteristic parameter increases from 57.72mV/h to 67.37mV/h. The peak temperature difference of the battery in actual charging process fluctuates within the range of 1-4℃. And the peak temperature difference at individual time points can reach 6℃. As the operating mileage increases, the peak temperature difference of the battery does not show a significant deterioration trend.