Power saver mode

If the battery charge level drops to low levels, the phone automatically activates Power saver mode to conserve battery power until you can recharge it. From the Home screen, tap Apps > Settings > Power saver > Turn Power saver on. You can set the phone to activate Power saver mode immediately, when the charge drops to 10%, 20%, 30%, or 50%. If you turn off Power saver mode, when the battery charge becomes low, a notification prompts you to turn it on.