i've just tested this mod on cm9 alpha 8 and it works perfectly.
if it doesn't work check some things:
-have cm9 alpha 7/8 installed
-have system theme
-try to start from the "pure" SystemUI.apk, not a modded one
-after the installation of the apk, open the app "battery bar settings" and check if the bar is enabled
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?