BleepingComputer.com: Battery Issues

I use an HP Pavilion laptop and have been through 2 batteries and about 5 battery chargers. My main issue right now is with my battery: I bought a 12-cell battery about a year ago because my 6-cell was running out of juice. Now, a year into the new battery the battery has lost over half its capacity. It would run for 5 hours when I first bought it and now it runs about 2. What's more, I get a disturbing jump down when the battery reaches around 20%. I've attached a picture illustrating this problem. It essentially just loses all of its charge immediately when it hits that percentage.
Is there anything I can do about this or am I just stuck?

I am not sure if your using attached USB devices which tend to borrow power off of your laptop battery, thus shortening its charge life.

Also I am not sure if you are doing what the manual says about proper run-down and recharge cycles. I would read the manual and follow recommended cycles.

I am sure your laptop comes with a few power saving features which help slow down the battery discharge rate.