FWIW, I have had several Ryobi 18v batteries give up the ghost. Some were the original batteries and one was the Li ion battery. I found that it is just about as cost effective to buy than to try and rebuild it, either by someone else or DIY. A diligent search turned up this website, www.directtoolsoutlet.com
, which had a set of four Li ion batteries for $99.00 with free shipping. They don't have the button to show the charge but no big deal. I was told they carry the same factory warranty but are blems that can't be sold retail due to scratches, etc. Bought four and they seem to be OK, so far. Might be worth looking into for whatever you need.
A diamond is how coal reacts under pressure.