Battery system

The invention relates to a battery system. A battery system is provided with a monitoring means for detecting the voltage and current between batteries included in a battery pack, and the temperature of the batteries. When the SOC deviation between the batteries exceeds a threshold value, the ECU increments the count value using the detection result of the monitoring unit. In addition, the ECU increases the count value when the positive electrode potential of the battery is lower than the threshold value using the detection result of the monitoring unit. The ECU diagnoses that the battery pack has deteriorated when the amount of change in any one of the count values is equal to or greater than a predetermined value. 本公开涉及电池系统。电池系统具备检测电池组所包含的电池间的电压、电流、电池的温度的监视单元。ECU使用监视单元的检测结果，在电池间的SOC偏差超过阈值时，将计数值递增。另外，ECU使用监视单元的检测结果，在电池的正极电位低于阈值时，将计数值递增。ECU在任一计数值的变化量成为预定值以上时，诊断为电池组发生劣化。