iPhone 11 battery health dropping fast after iOS 18.4.1 update

Battery health is a completely different matter than battery drain. Once your Battery Health drops below 80%, it is time to replace the battery. Since you got the phone in October of 2024, it was not a new device, so the history is unknown or if it possibly had the battery replaced with a non-genuine battery. Report back what you see for your Battery Health.

On average you will see Battery Health drop about 1% per month and the calibration will only occur when the battery has been charged to 100%. The drop is not linear and some months it will not drop at all and others will drop more.

Perfectly normal. After an update, your iPhone has lots of post-update background tasks to complete, mainly indexing which is creating and sorting your millions of bytes of data to be searchable. Your iPhone is also installing new features. All these tasks can make the iPhone work harder and as a result drain more battery, but only temporarily. After the tasks are complete, which is usually a few days, your iPhone should return to normal.

You can also read my User Tip which explains this fully in detail:

Addressing the Common Increased Battery D… - Apple Community

bastakaniha wrote:

Thank you!!

You’re welcome! The general rule of thumb is 36 to 72 hours. Let me know how it goes?