As cheap as these things are, I'd just buy a new one if you think it is helping your system. My opinion is don't waste your time opening it up, if it is anything like that one linked in the above video, there is no fixing it even if you do open it.
As long as it is fully discharged, I don't think it would hurt cutting it open, but it must be fully discharged. I of course don't recommend it if you don't have experience doing such things. Rubber gloves, and care using tools is of course necessary, but why bother as cheap as these are.
The cap in that video sure does look like they skimped out, it doesn't have concrete, but might as well.