Optimized Battery Charging is designed to reduce the wear on your battery and improve its lifespan by reducing the time your iPhone spends fully charged. When the feature is enabled, your iPhone will delay charging past 80% in certain situations. Apple uses on-device machine learning to learn your daily charging routine, only activating Optimized Battery Charging when your iPhone predicts it will be connected to a charger for an extended period of time.
While the algorithm aims to ensure that your iPhone is still fully charged when unplugged, this doesn't always happen. To ensure your battery charges to 100% you can disable optimized battery charging.
TURN OFF OPTIMIZED BATTERY CHARGING
Tap to open the Settings app from your home screen, then choose Battery from the settings menu.
Tap Battery Health from the battery menu, then toggle the Optimized Battery Charging switch to the Off position.
When prompted, tap Turn Off to turn optimized battery charging off.
The optimized battery charging feature will now be disabled and your device will immediately charge to 100% when plugged in to a charger.
● Optimized Battery Charging is on by default when you set up your iPhone or after updating to iOS 13 or later.
● 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, you can touch and hold the notification, then tap Charge Now.
● Some location settings must be enabled for Optimized Battery Charging to activate.
● Apple has yet to provide any data on how big an effect optimized charging has on reduced battery life. You can always enable optimized battery charging when you are on a regular schedule and disable it when you need your iPhone battery fully charged.
● If you feel your battery health is low, it's now possible to get replacement lithium ion batteries directly from Apple