I bought a used S2 8.0 and when it arrived it would boot up to the welcome screen and then reboot, with 65% battery. I unhooked the internal battery and it now runs off 3x 18650's and it is absolutely brilliant. I mention this because probably the most awesome thing about these tablets is the fact that they are incredibly easy to replace the battery having a plastic back and the battery is in fact under the plastic back. Samsung weren't sadistic toward their customers at this point.
All you need is a very good quality suction cup, I wouldn't expect the type of ones that come with replacement phone screens to work, but it might. There are no screws or anything just plastic clips the entire way round, they will likely break but you can use a thin double sided tape or glue or butyl as blutak or whatever you like to hold it back on, it will still kind of clip back together nicely just not strong enough so needs a little bit of sticky help and it will look just find if you take care.
There should be YouTube videos or walkthroughs if you look, but I thought I should mention it, because if you are having this problem, your battery is toast. And who can afford to limit this CPU, especially if you are using stock ROM, replacement battery is reasonably cheap, $25 give or take.