How to increase battery health

You probably can't do anything about that. Batteries decrease in health as they get older and are used by you. You can just try to do your best to make it last longer.

To learn about 'Maximizing Battery Life and Lifespan', click here --> http://www.apple.com/batteries/maximizing-performance/

Click on this link about 'iPhone Battery and Performance' to read about the battery health feature and what is considered normal performance --> https://support.apple.com/HT208387

- Requires iOS 11.3 and for iPhone 6 and newer iPhones only, not iPad or Watch.

Click on this link to read 'About Optimized Battery Charging on your iPhone' --> https://support.apple.com/HT210512