If your phone’s battery runs dry a little too quickly for your tastes, Android Lollipop’s battery saver is for you. It can help boost your phone’s run time, and it only takes a few minutes to set up.
Battery saver mode: A primer
Many Android apps will automatically sync in the background throughout the day to fetch new information from the Internet—for example, the Gmail app will fetch new mail periodically, and the Twitter app will continually get updates on whether anyone retweeted or mentioned you, all in the background.
Battery saver mode suppresses this sort of background app refreshing and throttles down your phone’s performance—among other things—to extend your battery life. The tradeoff, of course, is that you give up some processing speed and convenience on your phone. Your phone will feel sluggish and unresponsive, but at least you'll have something to tide you over until you can get back to a charger.
Battery saver mode switches itself off when your phone is connected to a power outlet, however.
Setting it up
Battery saver mode’s controls are buried in the Settings app: Open the Settings app, then navigate to the Battery section—it’s under the Device heading. You can get here more quickly by tapping the battery percentage reading at the top of the Quick Settings shade.
Next, tap the menu button—denoted by three dots—and then tap Battery saver. On the following screen, toggle the on/off slider switch to the “on” position.
And...that’s it. when you turn on battery saver mode, the status bar and navigation bar at the top and bottom of your screen will turn orange. to turn off battery saver mode, slide down the notifications screen then tap Turn off battery saver.
Battery saver has one more trick it can pull off—it can kick in automatically when your battery gets low. To use this feature, go back to the battery saver screen in the Settings app, tap Turn on automatically, and then tap either at 5% battery or at 15% battery. Battery saver will now kick in whenever you reach the low-battery threshold of your choice.