while plugged in ipad will keep flashing in and out of charge

basically, i have an ipad 2 that i have had for a year and a few months. since three days ago, while is is plugged into the wall using the apple charger that came in its box, it has been saying 7% (or whatever%) charged with the bolt then goes back to not being charged then charged,not chaged and repeating that on and on until i have taken out the charger. i dont know what to do! i have tried taking out the charger and putting it back in and also tried fully turning it off whith no effect. there are no other chargers that i have except my dads old ipod charger and the same thing happens with this. please get back to me if anyone knows what to do!