Depending on the stage of deterioration, nickle cells can be brought back in a few different ways. First, I would simply crank up the peak mv and keep an eye on the pack so you can stop it yourself. If it works, you would simply want to manually stop the charge process once the pack has reached 125F. If it does not work, you will just keep false peaking and other methods must be used. After a few cycles the pack should work correctly with 4-5mv cutoff. Remember that you must stop the process yourself if you turn up the peak detection, or you risk overcharging the pack. Other than that you will not do any harm by turning up the peak mv.

Charging at 1/10C for 12-15 hours is probably the most common method, because it seems to work and it is safest. Again, you will likely need to turn up your peak detection, but at the ultra slow charge rate there is no risk of overcharging, since the pack can bleed off excess as heat faster than the charger is supplying it. The pack could be warm by the 3rd hour, but you should give it full time to equalize the cells.

A method that I like is what I call "zapping" them. It is extremely dangerous, stupid and could seriously injure someone, so I do not recommend it unless you are comfortable with the possible outcomes. But this method has given me extra packs when I couldn't afford new ones. I disassemble the packs and "zap" each cell, one at a time, with 20A 12V, for just a moment at a time until the cell reaches appx. 100F. Then cycle the cell as usual and measure its output. I have had cells explode nearly instantly, and I have had some that still didnt work, but I have had several packs worth of cells come out much better. This is obviously a desperate attempt, but it can yield good results if you have no other choice.

Back when I was a starving young adult I would raid the battery recycling bins at Home Depot and Lowes and make awesome packs from seemingly dead cells. I even came out with a few homemade "matched" packs that performed better than some of my friends $80 "matched" packs. I recommend going Lipo if you can, but if not I would try the first two methods. If they dont work I highly recommend buying new packs, unless you are crazy and broke like I was back then.