I really need your help. My notebook (Dell latitude C840 running Windows XP professional) works perfectly with AC but it will stop charging the battery at about 17% (charging whole night, still 17%). I thought the battery was dying and bought a brand new replacement. To my surprise, the same thing. Of course the 17% battery can last only a few minutes before getting warning to switch to AC. What's wrong with it? Thank you in advance for your help.