Iconia B1 touch screen issue, full battery discharge?

Hi,

 i seem to have an area of the screen that has become un resonsive to touch.  If you hold the device in portrait mode it starts about 2cm down from the top of the screen, right across the width of the screen in a 2cm band.

My son has had the device  for about 5 months, and it developed a similar issue after about a month.  I tried a factory reset, made no difference, so it went back to Acer.  Thy sent it back and reported they had to do a full battery discharge to correct the problem.

Now the issue seems to have come back, and i am in the process of trying to wring every last drop of battery life out of the device, but as yet problem is still there. Even through I have not charged it for over a day, every time I come back to the device every couple of hours, it still boots up so still has a  bit of charge left in it.

Is there anything I can do to permofm a full battery dicharge without having to send the device back to acer?

regards

Manney