You are using your mobile device in battery mode and need to reduce power consumption to preserve the battery.
To save power, set CPU power options to scale the CPU frequency down.
Respective Tray Icon:
Tray Icon Name
Icon
Where to configure
CPU Power Plan
Menu path: Setup > System > Power Options > System
Setting CPU power options:
Click the CPU Power Plan icon in the system tray.
The context menu opens.
Select the appropriate mode.
Here you can find additional instructions concerning the power management:
Define the CPU Power Plan,Critical Battery Level, Standby Time or Suspend Time,Brightness reduction, and Shut-down Options. See the manual, chapter System > Power Option > System.