iOS 9 and later provide users with the ability to enter power-saving modes.
As per Apple IOS 9.0 update ( source : https://developer.apple.com/library/ios/documentation/Performance/Conceptual/EnergyGuide-iOS/LowPowerMode.html)
“Users who wish to prolong their iPhone’s battery life can enable Low Power Mode under Settings > Battery.
Once enabled, Low Power Mode changes the battery indicator in the top right corner to yellow, reminding users that their device is running in a more efficient state.
In Low Power Mode, iOS conserves battery life by enacting certain energy-saving measures. For example, the system may:
- Reduce CPU and GPU performance
- Pause discretionary and background activities, including networking
- Reduce screen brightness
- Reduce the timeout for auto-locking the device
- Disable Mail fetch
- Disable motion effects
- Disable animated wallpapers
The mode automatically disables when the battery level rises to a sufficient level again.
Impact on Apps
Your app should take additional steps to help the system save energy when Low Power Mode is active. For example, your app could reduce the use of animations, lower frame rates, stop location updates, disable syncs and backups, and so on.
What if your App is resource intensive, and user is trying to use the App when iPhone is in the low power mode? You App might crash. Regardless of the scenario, You need to make sure your app works and the best way to do that is to conduct mobile app testing on real devices. You need to put your App through rigorous testing on low power scenario on real devices.