Some MacBook Pro owners have noticed that their battery is swelling and no longer charges properly. Based on reports from Appleis Discussion boards, symptoms include batteries that fail to charge completely, computers shutting down while there is still a significant charge left, erratic trackpad behavior, and mouse button sticking problems.
In more extreme cases, the battery swells enough to bulge the bottom of the laptop case. MacMedics has pictures of a MacBook Pro battery that swelled enough to split its case.
A swollen battery poses a potential fire hazard, and shouldnit be used. If you have a MacBook Pro battery thatis swelling, Apple will replace it. Just contact AppleCare or pay a visit to your local Apple store.