Changing the length of time before the lock screen shows up, known as screen timeout, and brightness of your device can impact your battery life. Decreasing the time of inactivity before your device goes to sleep and lowering the brightness of your device can help extend your device's battery life.
From the Home screen, drag down the Notification Panel.
Tap the Settings icon.
Select your preferred screen timeout duration.
Note: Decrease the screen timeout to help extend your phone's battery life.