Replacing the battery on your MacBook Pro 15"Unibody 2.53 GHz requires a 1.5 mm flathead screwdriver to remove the five-point Pentalobe screws securing it to the upper case.
Use this guide to replace an old or faulty battery. If your battery is swollen, [[What to do with a swollen battery|take appropriate precautions|new_window=true]].
Summary
If your battery no longer holds a charge, use this guide to replace it.