Elecom M-XGS30BB User Manual page 10

4) Slide the power switch on the underside of the product to the ON position.
The LED will light up for a period of time.
* When the battery level is running low, the LED will blink for a period of time.
Power-saving mode
When the mouse is left untouched for a fixed period of time while the power is ON, it
automatically shifts to power-saving mode.
The mouse returns from power-saving mode when it is moved.
* Mouse operation may be unstable for 2-3 seconds after returning from the power-saving mode.
Replacing the battery...
1) Remove the battery cover.