Study on battery pack consistency evolutions during electric vehicle operation with statistical method

摘要

: The consistency among lithium-ion battery pack is an important factor affecting their performance. In order to investigate the battery pack consistency evolutions and influencing factors from statistics point of view, long-term battery data of two trolley buses are collected. Two parameters including the internal resistance and open-circuit voltage (OCV) are chosen to describe battery pack consistency in the study. The mathematical relationship between the battery pack OCV standard deviation after a period time and the intimal standard deviation with polynomial model is established. It is proved that the model error is within 6%. It is demonstrated that battery temperature has the greatest impact on the internal resistance consistency of the battery pack through correlation analysis. The initial SOC inconsistency and temperature of the battery are two key factors affecting the battery pack consistency based on the operation data, providing a foundation for battery consistency improvement.