Discharge the battery completely and recharge the
For many users, simply unloading their iPhone completely and then reloading it completely solved their problem. A kind of battery calibration.
Note that this only works when the problem is due to a bad display of the percentage.
Restore your iPhone as if it were new
The next step if the problem persists will be to restore your iPhone device as if it were new, ie by deleting all its data.
Do not forget to make a backup of your data before doing anything!
- Connect your iPhone to your computer
- Launch iTunes
- Choose Restore
- Once restored, choose to restore from a backup (the one previously done)
Contact Apple Support
If the problem persists even after these actions, you will only need to contact the Apple support service to resolve it or get them to help you.
It is obviously possible that your battery is malfunctioning and if your device is still under warranty, Apple will take care of it free of charge after inspection of it.