Battery is not charging despite SMC reset
Problem Solved
The battery was fine and the problem was with the charger. It seems that the charger couldnt transmit enough power to charge the computer while it was in use.
I opened the casing of the charger and observed that 2 capacitors were swelled. I changed them with new ones (I found them in a video receiver). 
Now its working like the first day I got it.