How do you know when iPhone battery needs replacing?

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Tags

1. #shops
2. #charge
3. #nearest
4. #repair
5. #serviced
6. #apple
7. #store
8. #settings
9. #third
10. #phone
11. #party
12. #replacement
13. #screen
14. #shape
15. #battery
16. #needs
17. #notification
18. #enough