What's the deal with my laptop battery?

So my laptop normally lasts for 2 hours. I have had it set to shutdown when it dips to 10% charge. Recently it starting shutting down after only a half hour.

So to see what happening, I've disabled the shutdown so I can drain it completely (sometimes that helps a battery). Its been more than a hour since it went below 5% and the battery still hasn't discharged completely. Got the wi-fi going and browsing around. Maybe I should watch some videos.