When you have connections such as Wi-Fi on while the phone is in sleep mode, some apps may still continue to use the battery. Starting from Android 6.0, battery optimization is enabled for all apps by default which helps prolong battery standby time when you're not using the phone.
The phone needs to be sitting idle for an extended period of time before battery optimization takes effect.
Turn Battery Optimization Off in Apps
If there are apps that you don't want battery optimization enabled, you can turn the feature off in those apps.
- Tap > > Settings.
- Tap Power.
- Tap Battery optimization.
- Tap Battery optimization > All apps to see the complete list of apps.
- To turn off battery optimization in an app, tap the app name, and then tap Don't optimize > Done.
- Repeat this process to turn off optimization in other apps.
Note: To filter the list and see which apps have battery optimization disabled, tap Battery optimization > Not optimized.