Although you will not see the Battery Updater file in the Extensions folder, Mac OS 9 includes the functionality of the Battery Updater 1.0 extension installed by the Battery Reset 2.0 software. For iBook owners with Mac OS 9 installed this means there is no reason to install the Battery Reset 2.0 software. The same holds true for PowerBook (FireWire) owners.
PowerBook G3 Series owners with Mac OS 9 installed may still want to install the Battery Reset 2.0 software to get the Battery Reset application. This application will reset a battery which may have been damaged in a certain way. The Battery Reset application is not needed, and will not work on an iBook or PowerBook (FireWire) computer.