EDIT: The kindle firmware interrogates the battery to verify that it is an AUTHENTIC amazon-approved battery. However, battery manufacturers can (and do) create clones that will pass the authenticity check, even if they do not contain all required safety features. Cheap replacement batteries may not be as safe a REAL authentic approved batteries.
I always wondering that why the authentic charger can only charge the battery. Why they do not provide an AC Adapter like that for laptop which is capable to run the device without the battery?