Upgrade to iOS 10.2. 1 or above;
Open Settings-Battery. If you see "iPhone battery may need repair", your battery is unhealthy, as shown in the following figure; If you don't see it, it means no problem.
In addition, the problem of automatic shutdown of iPhone seems to have been solved. According to Apple, there are two kinds of automatic shutdown problems:
In a few iPhone 6s devices produced from September, 20 15 to June, 20 10, a battery element was exposed to the air for too long before being put into the battery pack, resulting in abnormal automatic shutdown.
IPhone 6 and 6s batteries are normally worn out, and the old batteries may have unstable power supply during use, resulting in an emergency automatic shutdown of the system.
The above two situations are different. The first situation has been solved by replacing the battery. As for the second case, Apple said:
For 6-and 6-s users who have experienced automatic shutdown, due to the upgrade of iOS 10.2. 1, the frequency of automatic shutdown of iPhone 6 has dropped by more than 70%, and that of iPhone 6 has dropped by 80%. If it is still automatically turned off, iOS 10.2. 1 will automatically restart after the iPhone is turned off, and there is no need to connect the power supply to restart it as before.
In addition, the above two situations seem to have nothing to do with iPhone 7, so I would like to ask, Apple 7 users, have you ever encountered an automatic shutdown?