One of the new features added in iOS 13 to the iPhone is Optimized Battery Charging. This feature is designed to reduce an iPhone’s battery aging and help improve its overall life. By reducing the time the iPhone spends while being fully charged, the feature helps to reduce battery aging.
When this new feature is enabled, iPhone analyzes and learns from your daily charging routine, so you can wait until you have to use your device to finish charging past 80 percent.
So if you recharge your iPhone overnight and learn that you’re going to get up at 7AM, it quits charging when the battery achieves 80 percent and after that revives at the perfect time, so you get 100 percent charge when you wake at 7.
A new option helps slow the rate of battery aging by reducing the time your iPhone spends fully charged. iPhone learns from your daily charging routine so it can wait to finish charging past 80% until you need to use it.
You can enable or disable the new Optimized Battery Charging feature by going to Settings > Battery > Battery Health.