Set keyboard backlight to zero instead max value.

If the keyboard backlight brightness value is not set by the user or outside the valid range, it is disabled instead of being set to maximum brightness. Disabled keyboard backlight also increases battery life by lower power consumption (keyboard backlight at maximum brightness can consume up to 0.7 W).

Most users disable keyboard backlight and use it only for exceptional circumstances, like working at night in an unilluminated workspace.