My Lenovo laptop has been having this issue for the past week or so. Basically if I turn my laptop on it will say it is at 50% and then after about 30 seconds it will die. If i plug in the laptop it will stay alive but it wont charge at all. I'm bascially walking around with a light desktop and i really need this fixed seeing as how my laptop is less than a year old
its either the battery or the charger, both should be under warranty and a replacement should be easy to get.
if warranty is not an option you will need either a spare battery or another charger to verify where the actual problem lies. if not the batter or the charger it may be the charge controller in the laptop itself.