1. The battery health is less than 80%, and the iPhone is usually charged more than 500 times, that is, the battery life will be reduced and the capacity will reach about 80% when the iPhone is used for about 14- 18 months. It is recommended to change the battery. Because Apple takes 80% as the threshold, if it is lower than 80%, the system will forcibly turn on the performance management function, and the mobile phone will become more stuck. It is recommended to replace the battery.