I put the ipad on the wall adapter charger today and it only went up to 18% from dead and I didn't use it at all while it was charging. It was put on the charger around *:30 and taken off around 5:30
When connected to the wall charger does it show the iPad as charging? Some people here have reported that their wall charger have died. Also, try another cable if you have one. If you do not have one connect the iPad to you computer to help see if the cable is good.
Are you sure the wall socket is working? Have you unconnected and reconnected the three connections (wall socket to charger, cable to charger, and cable ti iPad. Maybe you have a bad connection. Try leaving it hooked up to you running computer for a while to see if it charges when asleep.