It's not safe, but I have restored batteries by "juicing" them cell by cell. I would use a parallel board to plug them into and do a quick plug and unplug a few times. this will cause the traces to heat up quite fast and you will likely kill your board if plugged in for too long, so don't use a good parallel board. But only do it with the balance leads, not the main lead. I have also done it with a paperclip, however that clip can get hot as well, so use pliers.
Reason for the balance plug, rather than dealing with 22.2 volts, you are only dealing with 3.7 volts. Less sparking (if any). Just remember, You are effectively dead shorting the "good" pack, so it's very hard on it. Only use a pack that you are not worried about losing. I also go across the balance plug as well. cell 1 to cell 1, cell 2 to cell 2 and so on. Never cell 1 on the good pack to all cells on the bad pack.
