Well the point of replacing is you replace the battery, as for replacing the cells, you'd probably have to be a decent electrical engineer and know a good source for the cells (you can't exactly get them at staples). What I suggest you do is find out what type of battery you need (most PC laptops don't use proprietary batteries) and you then don't have to get OEM, you can just find any reliable battery meeting your requirements, I'm guessing it'll be a lot cheaper. Just make sure not too cheap, and buy from a reliable source.