Recently my Kindle 4 has, at night, started to go from fully charged to half charged. I've tried looking up possible reasons or solutions for the problem, but nothing has worked. I've tried seeing if the Kindle is indexing any books and it's not. I've tried a reset, and a factory reset and that hasn't worked either. I'm at a loss as to what could be causing the problem, and I have no idea how to go about fixing it.
I would really appreciate any help.