I have a 15" macbook pro with a 6-cell battery in it which is 3.4years old and not charging properly and gives the error "service battery" I have tried everything to fix it so now I want to replace it. In looking, I see you can get both a 6-cell and a 9-cell battery, will a 9-cell work in my macbook?
I wouldn't trust or recommend any non-Apple battery, due to the number of problems reported with "knockoff" batteries. Also, there is no assurance that knockoff batteries have the same charging technology that Apple uses, involving the battery, the MagSafe adapter and the Mac's logic board.
The link below should answer most, if not all, of your battery/charging questions. If you haven't already done so, I highly recommend you take the time to read it.
