A battery module is provided. The battery module includes a battery set, a voltage measurement unit, a temperature measurement unit, a matrix calculation unit and a mix algorithm unit. The voltage measurement unit measures a voltage matrix of the battery set. The temperature measurement unit measures a temperature of the battery set. The matrix calculation unit calculates a norm of the voltage matrix. The mix algorithm unit reduces a remaining capacity of the battery module by a first predetermined rate if the change of the norm is larger than a predetermined value and the rise of temperature is larger than a predetermined difference for a predetermined time, and reduces the remaining capacity of the battery module by a second predetermined rate if the change of the norm is larger than the predetermined value and the rise of temperature is not larger than the predetermined difference.