Here's how to check if your iPhone needs a new battery
iPhone Battery and Performance - Apple Support
Is it true that if your iPhone battery health goes below 80% within a year of buying it, you get a battery replacement for free or a replacement phone? - Quora
How and when to replace your iPhone's battery | iMore
iPhone Battery Health explained: How you can control it
What battery health percentage should iPhone batteries be replaced? : r/ios
Is it true that if your iPhone battery health goes below 80% within a year of buying it, you get a battery replacement for free or a replacement phone? - Quora
iPhone Battery and Performance - Apple Support
How to Tell if You Need a New iPhone Battery | PCMag
iPhone Battery and Performance - Apple Support
How to get Apple's $29 iPhone battery replacement - CNET