You might also want to search this forum for Wally's posts on this subject. He's done the most thorough experimentation and research of anyone I know. I'll briefly share my experience: I've swapped out cells to rejuvenate battery packs for 'books as well as for Dells and VAIOs. I've had mixed results. Some packs worked great right away, others never did. Most packs store data about the battery capacity, and can retain that information even with new cells. Unless you have a utility to reset that type of information, the recelled pack may not function any better. There are other factors that can get in the way as well, as Wally has shown. The full science of it remains to be revealed (at least to me).