Apple’s upcoming iOS 14.5 will have an update which fixes battery issues on the iPhone 11 Pro Max, iPhone 11 Pro and iPhone 11.

Support document has outlined that battery health reports have inaccuracies, and that the affected devices may experience sudden performance drops or battery drain.
The iPhones will undergo recalibration in terms of peak performance and maximum battery capacity within regular charge cycles. Apple says the process may take a few weeks before the maximum capacity is correctly displayed.
iPhone 11 owners will see a status notification on Settings, Battery and Battery Health. Once the update is complete the real battery capacity and performance should be posted in the same place.
Recalibration and may fail, in which Apple refers the iPhone user to the nearest service center. An Apple Authorized Provider can replace the battery free of charge. Apple says the issues do not indicate physical danger and that the iPhone’s battery can still be used as normal.