You plug in your iPhone overnight and it sits at 80 percent. Before you assume something is broken, know that this is usually deliberate. Apple lists three reasons, and each has a different fix.
1. Optimized Battery Charging
Apple says iOS 13 and later use Optimized Battery Charging to slow battery aging by reducing the time your iPhone spends fully charged. The phone uses on-device machine learning to learn your daily charging routine, so it can wait to finish charging past 80 percent until you need it. If you charge overnight, your phone may hold at 80 percent and top up before you wake.
2. The battery is too warm
Apple says your iPhone might get slightly warmer while charging. If the battery gets too warm, software might limit charging above 80 percent to extend battery life. It charges again when the temperature drops. Move the phone and charger somewhere cooler, take off a thick case, and keep it out of direct sun.
3. A charge limit on iPhone 15 and later
With iPhone 15 models and later, you might have a Charge Limit that stops charging past a set percentage. If you want your phone to charge past 80 percent, change the limit in the battery settings. Apple has a separate page, “Charge Limit with iPhone 15 models and later”, for the exact steps.
Is 80 percent bad?
No. Apple’s whole point is that spending less time at full charge helps the battery age more slowly. Apple also recommends avoiding hot environments, which ties in with the second reason above. For the full picture on battery aging, read our guide to iPhone battery lifespan and charge cycles.
When it is not about 80 percent
If your iPhone will not charge at all, or charges very slowly, that is a different problem. See our guide to what to do when an iPhone will not charge.
Frequently asked questions
How do I make my iPhone charge to 100%?
Check whether Optimized Battery Charging or a Charge Limit is on, and let it cool if it is warm.
Does Optimized Battery Charging hurt anything?
No. It is designed to slow battery aging.
Sources
Last checked November 3, 2026. Apple changes its instructions between updates, so if a menu looks different on your Mac, check the linked Apple page.
