Battery service message
Hi,
I am using Iphone 11 pro.
When my phone’s battery health got recalibrated in IOS 14 update it went to 100% health but next update brought the battery service message along with 100% health.
Any solution for this?
You can try to manually recalibrate the battery and/or perform a factory reset.
For a manual recalibration:
Turn Off Low Power Mode
Lower The Screen Brightness
Disable Background App Refresh
Turn Off Location Services
Drain your iPhone battery by watching videos or doing other things until it turns off automatically. Then leave it and do not use it for several hours.
Charge your iPhone with an official Apple cable. When it turns on, swipe it off and keep charging for several hours.
Don't plug the cable. And turn on your phone and then force restart it in the charging state. The final step is that you can enable the functions mentioned in last part in order to use your phone normally.
Source: https://www.tenorshare.com/iphone-tips/how-to-calibrate-iphone-battery.html
Some people had solved this problem with a factory reset, but since your iPhone has some year, I would trust more of the warning message rather than battery health, even after the recalibration, so I would simply use it until I bring it to an Apple Store for a battery change. :)