You should consider getting your battery replaced after a year's worth of Mostly plugged in use. Piece of garbage, and I STRONGLY recommend AGAINST buying any laptop that uses this type.
Always Use A Battery Meter
By Woodstockfrom Chapel Hill, NC on 5/14/2012
When testing a battery for the first 3 months you should use a meter to check MAH and retain capacity. This will also show the time you have on the current charge. I am running Windows 7 on an older laptop, this battery 3:15 run time.