An extension for gnome shell that will change the screen brightness when the machine is running on battery power.
In the default dim-by-value mode, the screen will be dimmed to 50% brightness when running on battery. When the brightness is changed, the new brightness level will be remembered whenever you're on battery power.
In the new dim-by-percent mode, the screen will be dimmed to 50% of the plugged-in brightness level. If the brightness level is at 75% when your machine is plugged in, once your machine is on battery power, the brightness level wll be changed to 38%. This is useful in environments where the light level changes frequently.
git clone git://github.com/nailfarmer/gnome-shell-dim-on-battery-extension.git
cd gnome-shell-dim-on-battery-extension
cp -r dim-on-battery@nailfarmer.nailfarmer.com ~/.local/share/gnome-shell/extensions