iPhone battery health check: real health, cycle count

Last updated: October 22, 2026

Settings › Battery › Battery Health shows one number, Maximum Capacity. It is rounded, it can stay the same for weeks while the battery keeps ageing, and a replaced battery can show 100% whatever it is worth. The figures behind it are in a file the iPhone already writes every day.

Get the analytics file

1. Open Settings › Privacy & Security › Analytics & Improvements.
2. Make sure Share iPhone Analytics is on: iOS writes the files only while it is. Turned on today, the first file comes tomorrow.
3. Scroll to the end, tap View Analytics Logs (Analytics Data on earlier iOS), and open the newest file whose name starts with Analytics- and has .000 in it. If the list has a search field at the bottom, type Analytics- in it; the newest files are at the end.
4. Tap Share, then DeviceBox.

Each day has two analytics files, and the battery figures are only in the larger one: the one with .000 in its name or, on a day when neither has it, the one with the later time. Files with session in the name hold none. If DeviceBox says a file holds no battery data, share the other one from the same day.

What DeviceBox shows

• The health iOS shows, next to the health worked out from the battery's own capacity figures, counted the way Settings counts it and strictly.
• The cycle count and the capacity now, in mAh.
• Whether the figures agree, and whether they are normal for the battery's age and the model.
• How long the iPhone has been in use, from the battery's own counters.

The file is read on your iPhone; nothing in it leaves the phone.

Checking someone else's iPhone

The analytics file of another iPhone can be shared to yours by AirDrop. DeviceBox tells you when the file does not come from the iPhone it runs on, and asks which model it is from when the file does not say. See Check a used iPhone before you buy it.