With my Fujitsu Lifebook P1620, the battery that came with it is loosing charge capacity. It is discharging faster than I anticipate (about 1 hour of life only).
The solution has to do with a COMPLETE discharge of the battery and then fully recharge it for minimum 48 hours.
I have yet to try this, but there are other methods.
Ebay has an well organized methods to treat such batteries.