When your tablet is off, blow into the charging hole, then use an open safety pin to dislodge any dust or dirt. Then blow again into the hole. Also ensure that the charger is clean. That should take care of your problem.
Please join me in congratulating IronFly who is the first Acer Community Member to achieve the rank of ACE Pathfinder. IronFly has shown a consistent willingness to help others and has worked hard to earn this new Rank. Congrats and Thank You IronFly.