Why does my Smartab Tablet shut down at 80%?

A

AC Question

So I've had my Smartab Tablet for less then a year, and now the battery is way out of whack. My tablet will shut down at around 80%, then, if I wait a minute or two, I can turn it back on and it will be where it was with battery was, if not a little lower. And after that the battery will die kinda fast.