This is quite often a sign that you're using the wrong AC adapter. The adapter has to have a high enough output current to be able to both power the laptop AND charge the battery simultaneously. Another possibility is that the charging circuit (on the motherboard) has failed. You'll have to have that checked out at a shop. The third elephant in the room is the use of cheap 3rd party batteries that do not meet the OEM specs. If you are in fact using OEM batteries then you may also have just gotten ahold of a bad one (they do have a shelf life).