I recently put on my laptop and when it booted up ok the screen was dull as if the battery was low but the icon said it was charging. It remained at 2% and never rose up to full charge. When I take it off mains power the screen brightens up like it was fully charged but i get a message saing i should switch to mains outlet as the power was low. Any body any ideas what is going wrong. I tried another power adaptor but still the same result.