tablet battery drain?

[Shadowmeph]

I bought a cheap neutab tablet few months back I mostly use it for a remote for kodi on PC and to watch shows/ movies that I drag and drop onto tablet from my PC . sometimes when I am moving a movie or show onto the tablet ( plugged into USB into PC) I forget to unplug the tablet from PC. there has been a couple of times that I cannot fire up my tablet like the battery is drained.
My theory is that when I forget to unplug my tablet from my PC and it is left over night and my PC goes to sleep it is draining the tablets battery . do you think that my theory is correct or is there something wrong with this cheap tablet.

on a different note I am curious which program people use on there tablets to watch shows I am currently using VLC which works great I am just curious because i tried the google one and it doesn't play a few of the Shows movies I have VLC seems to play all but is a little slow to load up