I charged my laptop for more than 12 hours it was still not charged.

Sometimes the cord may be plugged into the computer, but it may not be properly plugged into the AC adapter properly. Make sure that the cord connecting the computer to the AC adapter is fully plugged in. If the cord is connected to an electrical outlet extender, make sure it is on and fully connected to an outlet. It could be off and not transmitting the charge. If the cord is directly connected to an outlet, then firmly push the cord into the wall and check for a charge. If it is still not working, try a different outlet. You could have a short and may simply need to plug it elsewhere. If the battery still does not charge you may have a malfunctioning battery which needs to be replaced. Check out this simple guide for battery replacement Hope this helps!