Lithium-ion batteries—the technology powering your iPhone—degrade significantly faster when they are held at exactly 100% capacity for extended periods of time. If you plug your phone in every night before bed, it usually hits 100% within two hours. It then sits on the charger for the next six hours, generating unnecessary heat and microscopic chemical stress that slowly destroys the battery’s maximum lifespan.
To combat this chemical degradation, Apple introduced a brilliant machine-learning feature called “Optimized Battery Charging.”
How Optimized Charging Works
When this feature is enabled, your iPhone actively analyzes your daily routine. It learns exactly what time you usually wake up and unplug your phone.
When you plug your phone in at midnight, it will rapidly charge to 80% and then intentionally stop charging. It will hold the battery perfectly at 80% for the entire night, significantly reducing chemical stress. Then, exactly one hour before your alarm goes off, it resumes charging, pushing the battery to 100% just moments before you wake up.
How to Enable Optimized Charging
This feature is often enabled by default on newer iPhones, but it can accidentally be disabled during major iOS updates.
- Open the Settings app on your iPhone.
- Scroll down the menu and tap on Battery.
- Tap on Battery Health & Charging.
- Look for the toggle switch labeled Optimized Battery Charging at the bottom of the screen.
- Toggle the switch to the On (green) position.
Overriding the Schedule
Because the system relies on a predictable routine, it can occasionally miscalculate. For example, if you usually wake up at 7:00 AM, but you need to wake up at 4:00 AM for an early flight, you might unplug your phone to find it is only at 80%.
If you know your routine is going to change, you can easily bypass the optimization hold.
When your iPhone pauses charging at 80%, a silent notification will appear on your lock screen stating: “Scheduled to finish charging by [Time].” If you need a full charge immediately, simply press and hold that specific notification, and tap “Charge Now.” The iPhone will instantly resume fast-charging to 100%, ignoring its learned schedule for that single night.