How to check iPhone battery new or old or changed?

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

- With iOS 13 and later, your iPhone learns from your daily charging habits to improve the lifespan of your battery.

- Settings > Battery > Battery Health > Optimized Battery Charging

Click on the link to read 'About the battery and performance of iPhone 11 and later' --> https://support.apple.com/HT210557

- About performance as batteries age

- Check battery health on your iPhone

If you have iOS 14 or 15 go to Settings/Battery/Battery Health. If it displays battery health then the phone has an Apple battery. There is no direct way to know if it is new or replaced by Apple. However, if you have a Mac the free Coconut Battery app for the Mac can tell you the manufacture date of the battery.