Plugged in W4 820 to charge and get a red flashing light instead of steady light & won't charge

breside

I tried to turn on my Acer Iconia W4 820 and it wouldn't turn on.  I assumed that I left it on sleep instead of powering it down, so I plugged it in to charge.  I noticed that the red light that normally comes on when charging was flashing off and on rather than being steady red.  I thought that maybe the charge was lower than normal.  I left if overnight, but it was still flashing in the morning and hadn't charged.  Normally, the light turns green when the unit is charged.  When I pressed the power button and the windows button at the bottom of the screen the Acer opening screen displayed briefly with a low charge battery symbol.  I plugged it back in to charge.  The red light is flashing.  Any thoughts?