Some users found iPhone can be charged to 80% only even they charge long time. For this problem, users can check to see if below two reasons:
Check out the Optimize Battery Charging setting:
With iOS 13 and later, Apple offer "Optimized Battery Charging" feature. This function is on by default, iPhone learns from your daily charging habits to improve the lifespan of users' battery, and suspend charging to more than 80% until user need it.
That is, if you maintain the habit of charging your iPhone before going to bed at night, your iPhone will charge to 80% overnight, and then to 100% before you wake up to check. If you have an irregular habit of charging your phone, after turning on this setting, you may encounter a situation where the phone is charged to 80% and paused when you need to use the phone.
When Optimized Battery Charging is active, a notification on the Lock screen says when your iPhone will be fully charged. If you need to have your iPhone fully charged sooner, touch and hold the notification and then tap Charge Now.
If user want to turn off the feature, go to Settings > Battery > Battery Health > Optimized Battery Charging.
Check if the device temperature is too high
With the arrival of summer, when used outdoors in direct sunlight, the mobile phone will have a relatively obvious fever; in addition, if user make a phone call or play a game of luck while charging, the iPhone will also heat up. Apple officially recommends using the iPhone in an appropriate ambient temperature.
If the iPhone's temperature is high, the protection mechanism will be activated, charging the phone at this time, the charging may slow down or even stop. When the device temperature is high, user should stop using the device and move it to a cool environment for charging, away from heat and direct sunlight.
After eliminating the above two situations, if there is still a problem of not being fully charged, user need to bring the device to the after-sales service for maintenance.
