Log Into Breece Explorer as administator. 

Press the tab "Configuration".

Select "System" on the right side.

Find "Automatic display radio coverage check"

Big battery icon

If "Enable Full Screen Low Batte:" is checked the battery icon will fill the entire screen.

Small Battery icon

If "Enable Full Screen Low Batte:" if unchecked the battery icon will only fill a corner. 

You can select witch corner the icon will be displayed in, in the "Battery icon placement:" menu.