An iPhone battery is designed for approximately 500 full charge cycles — that's two to three years of regular use. After that, the capacity drops below 80%, and iOS begins throttling performance to prevent the phone from shutting down under load. This is not a defect, but wear: the battery is a consumable part.
Three signs to watch for
- Maximum capacity below 80%. "Settings → Battery → Battery Health". This is Apple's official threshold.
- Unexpected shutdowns. The phone turns off at 20–40% and only powers on when charging. The most reliable indicator: it appears even when capacity shows 85%.
- Swelling. The screen rises above the frame, the back cover doesn't lie flat, the phone "rocks" on the table. Don't delay here at all: the battery is pressing on the display and may crack it, and a damaged lithium-polymer cell is dangerous.
What is not a sign of wear
Quick battery drain in the first few days after an iOS update — this is photo and search reindexing, it will pass. Heat during app downloads — that's normal too. And separately: the number of cycles itself doesn't matter if the capacity holds up. If your phone drains quickly but "Battery Health" shows 90+%, first check your apps — this is covered in detail in the article why iPhone drains battery quickly.
Will calibration help
Calibration does not add capacity. It only restores correct percentage readings when the controller gets confused: the phone shuts down at 40%, even though the capacity is high. One full cycle is done — discharge until shutdown, charge to 100% and keep charging for another hour. If the behavior doesn't change after that, it's the battery itself.
What is used as a replacement
Capacity and performance depend on what exactly is installed: a genuine Apple battery, a genuine part with controller, or a refurbished cell. The price difference between them is noticeable, so it's worth making an informed choice — the price list is on the iPhone repair prices page, and the batteries for repair shops are in the parts catalog. Replacement takes about an hour.