Low Battery Mode
Is it ok to use iPhone on low battery mode every time?
iPhone SE, iOS 14
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If you're not needing the reduced features, you can use Low Power Mode as often as you wish:
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When Low Power Mode is on, your iPhone will last longer before you need to charge it, but some features might take longer to update or complete. Also, some tasks might not work until you turn off Low Power Mode, or until you charge your iPhone to 80% or higher.
Low Power Mode reduces or affects these features:
- Email fetch
- Background app refresh
- Automatic downloads
- Some visual effects
- Auto-Lock (defaults to 30 seconds)
- iCloud Photos (temporarily paused)
- 5G (except for video streaming)
When Low Power Mode is on, the battery in the status bar will be yellow. You'll see 
and the battery percentage. After you charge your iPhone to 80% or higher, Low Power Mode automatically turns off.
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copied from: Use Low Power Mode to save battery life on your iPhone - Apple Support