User manual
Turn on Power Saving. The phone will let you know when your battery level goes
down to 20%, and again at 10%, and will ask you to turn on Power Saving. The
battery indicator in on the top right corner will turn blue while Power Saving is
enabled.
To manually turn on or off Power Saving Mode at any time, swipe down from the top
of your screen to open Control Center, then click . You can also go to [Settings] >
[Battery] and enable Power Saving.