Just a thought, do you have the same problem with the AC adapter?
If not, look at the battery charging board on the motherboard. (on the 8100 it was small board connected to the MB about center of the keyboard)
Try the AC adapater with the Battery in and out. Try it and take the battery out. Does the battery ever charge? Also make sure the AC adapter lines are not crimped or sharply bent. Some people wrap the cord arounf the converter and that causes undue stress on the wires.
Have fun
Ray