iOS 11.3 comes with a battery diagnosis feature that lets users find out if the battery of their iPhones needs servicing or not.
Checking how worn-out the iPhone battery takes just a few seconds. On the iPhone, launch Settings and follow the next path to see your score:
Settings > Battery > Battery Health (Beta) > Maximum Capacity
Depending on this Maximum Capacity score, you can determine whether you have to replace the battery or not. Apple says that once your battery dropped below 80%, this performance throttle kicked in to make sure no unexpected reboots occurred.
