I have a Thinkpad Edge 14 and I'm having two problems.
1, My Edge slows down when it's charging. I have a 9 cell battery. I recently got my motherboard replaced by lenovo because the charger was getting too hot and also laptop was slowing down when it's charging. However, I noticed that even after i got my motherboard replaced, it still slows down when it's plugged.
2, When I run my Edge on battery, the LCD color contrast randomly decreases. Also the brightness goes down too. I'm sure that the decreasing brightness is not due to power management. The brightness and color contrast slowly fades and it comes back to normal after 1-2 mins.
Did you find out what was going on with the laptop and the charge? i have the same problem, when I'm watching a video or something and i plug the computer it gets too slow...but if it is not plug it works really fine...let me know if you have any info...thanks!