First you need to to a Power Manager reset PMU reset) on your machine
http://support.apple.com/kb/ht1431
Then recalibrate the battery
http://support.apple.com/kb/ht1490
Keep in mind that batteries last from one to three years and they steadily lose capacity. Apple’s criteria is the battery should retain 80% charge after one year of use, and one year should have no more than 300 recharge cycles. If a new Apple battery is under 300 cycles and less than 80% capacity before 1 year is up, it may be eligible for warranty.
Coconut Battery is a little application that gives you more information about your battery’s health (Requires OSX 10.5 or higher) http://www.coconut-flavour.com/coconutbattery/