Charging your iPhone to 100% won’t instantly fry your battery. Why iPhone battery charging mattersAll iPhones use lithium-ion batteries, which naturally degrade with every charge cycle. How the iPhone’s Optimized Battery Charging worksThe feature works by learning your daily routine using machine learning. What you should actually do to make your iPhone battery lastTo extend your iPhone’s battery life, you should eable Optimized Battery Charging. If you own an older model, go to Battery > Battery Health & Charging.