Nook HD Will Not Charge

[pauly99]

I purchased a Nook HD for my mom a couple of weeks ago. She charges it when the battery is running low (between 9 and 13%) and when the battery shows that it has been charged and green, she turns the Nook HD on. Only the last few times it is showing a 13% charge even after the green light showed that the Nook had been full charged. What is going on here? Any help?