Here's how to check if your iPhone needs a new battery
How to Tell if You Need a New iPhone Battery | PCMag
HP Notebook PCs - 601 or 60X Error Displays on a Black Screen | HP® Customer Support
Use Low Power Mode to save battery life on your iPhone - Apple Support
Battery Terminology
Why you shouldn't calibrate the battery in your iPhone, iPad, or iPod
Low battery capacity - Apple Community
Battery Low, Battery Full Icon, Energy Symbol, Battery Charge. Color Symbol Set. Mobile Black Smart Phone Icon Gadget. Gray Color Stock Vector - Illustration of electrical, graphic: 138630178
How To Disable iPhone iOS 11.3 Slowdown With Battery Health Feature