iPhone 17 Pro battery stuck on 80% after charged.

Wait a few hours and check the battery percentage again.

If is still at 80% at that time, perform a Forced Restart on your iPhone.

Force restart iPhone - Apple Support

How to Adjust the Limit

If you want your iPhone to charge past 80%, you can change the charging optimization setting:

Go to Settings $\rightarrow$ Battery.

Tap Charging.

You will see options for charging optimization, including 80% Limit, Optimized Battery Charging, and None.

If you want it to stop at 80% less often or not at all, change the Charge Limit to a higher percentage or select Optimized Battery Charging (which still charges to 100% but delays the final 20%) or None (which charges straight to 100%).

On iPhone 15 models and later, Apple introduced a Charge Limit option that lets you set a maximum charge between 80% and 100%. If you set this limit to 80%, the phone will intentionally stop charging when it reaches that level.

Primary Reasons for Stopping at 80%

80% Charge Limit Setting: This is the most direct cause. You may have intentionally set the limit to 80% (or your iPhone may have prompted a recommendation and you accepted it). Lithium-ion batteries degrade faster when kept at a 100% state of charge, so limiting it to 80% helps preserve long-term battery health.

Optimized Battery Charging: If your Charge Limit is set to 100%, another feature called Optimized Battery Charging may be at work. This feature uses machine learning to learn your daily charging routine (like when you wake up) and will delay charging past 80% until shortly before it predicts you'll unplug the phone. This reduces the time the battery spends fully charged.

Overheating: If the iPhone's battery becomes too warm while charging, the software may temporarily limit charging to 80% to prevent damage. Charging will resume once the temperature drops. Try moving the phone and charger to a cooler location.