iPhone battery: when to replace it, and why 80% isn't a magic number
The “Battery Health” setting gives a percentage. It is useful, but it doesn't say everything, and above all it doesn't say when the phone will let you down.
A lithium-ion battery wears with every cycle. Apple shows its maximum capacity under Settings › Battery › Battery Health, and considers it due for replacement below 80%. In practice, problems often start before that threshold.
The real signs
- The phone shuts down while still showing 20 or 30%, especially in the cold or when taking photos.
- It gets hot while charging, or charging becomes very slow.
- iOS shows a service message, or throttles performance (menus that lag after an update).
- Battery life has halved compared with the first months.
- The screen or back is lifting: the battery is swelling. Replace immediately.
What a new battery changes
Recovered battery life, obviously, but also a phone that gets its speed back if iOS was throttling it, and that no longer dies in the cold. For a three- or four-year-old iPhone in good condition, it is the repair with the best ratio of price to years gained.
At the workshop
Half an hour by appointment, new tested battery, new adhesives and seal. On recent iPhones we explain the “unknown part” message Apple shows with any battery not bought from them: it has no effect on operation. Prices per model are on the prices page.
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