Recovering DeWalt 20 V-Max batteries that just won't wake up?

I have several batteries that have keeled over from having an inverter connected to them for a bit too long, and I've heard you can connect another good battery in parallel to get it to take enough charge that the charger that come with my tools will see it. However, when I do that, nothing happens. The dead battery remains dead and the full battery remains full, even if they are left connected together overnight. (Before you say I will burn my house down, I did this outside and away from the house, just in case things got a bit spicy, but they didn't.) I have also had the same thing happen with Milwaukee XC series batteries using a similar inverter before I realized this style device would do that. I have also tried connecting 12V batteries and chargers to them attempting to push enough energy back into them to where I could get them to show signs of life with no results, as well as disassembling a couple of them and attempting to charge the cells themselves. Do bog standard tool batteries of the name brands now have a lockout if drained too far, or what am I doing wrong? How can I get them to wake back up that I haven't tried?