Reviving batteries

[Mash Potato]

I’ve got GP 3700 cells, some are new, and some are a few years old.

I’m running an 11x2 checkpoint motor in a B44 with a 19T pinion on an indoor track just for info.

I’m having a few problems with some of the older packs dumping before the end of the race. The new batteries are fine, and so are some of the older ones. But a couple of the older ones seem to dump. They are all discharged to 1.0V per cell before being charged again.

Now although these “suspect” batteries are several years old, they have literally only been charged a handful of times in their life’s, probably less than 20 times. But they did sit for some time un-used.

So my questions are:
1) Have I mistreated these cells by leaving them standing (obviously this was not a good thing) and thus permanently damaged them?
2) Is there a way to re-vive them, and if so how long is it likely to last before they either die, or return to this state?