I have "pulsed" 14v NiCd packs for power tools using a welder and it works for me.  Some packs are still working years after.
 If the flightpack cell has very high resistance or has vented it won't help it.  I have spent time trying to salvage NiCd packs,making one out of two, etc... and decided it's not worth the time and now replace failing packs with LiFe flight packs.
If you are referring to a LiPo cell , just disable it and toss it.