The purpose of this paper is to obtain the important information of a power battery pack from the battery management system by analyzing the charging complete and discharging complete data records. We can observe the special status of a battery cell by the past data records. In addition, if combined with the charging and discharging time data, the battery management system can determine the aging degree of a battery cell, such that one can timely replace the corresponding battery cell. According to these data records, it can also help set a better battery balancing mechanism to increase cycle life of the battery, to properly adjust the battery capacity, and to avoid unnecessary energy consuming. Also, from analyzing the battery status information, one can adjust the battery balancing mechanism to improve voltage measurement accuracy.