Used to zap NiCd too, but had mixed results
They can take serious abuse, I don't think I've ever had one "go wrong"...
Biggest issue I've noticed is that the tendency is everything is ok until they get discharged to a certain point, and then the short recurs.
Best results were with capacitive discharge, PC front end power supply caps are a decent cup of juice to dump into them. High current is the key in my experience with them. Car battery and jumper cables works halfway decent too, but not quite as well.
The current needs to be intense but short. Leaving it connected doesn't gain anything but heat in the cell. They're tough, but I'm sure they have their limits...
Of course, its not as simple as just yanking the screws out of that dead PC... Current limiting for the charging is a must, and should be set up so that it takes several seconds to reach full charge so that you can give it a controlled dose (the energy in the cap increases with voltage). The other challenge is switching... I used (and killed in short order) a relay, but solid state would be preferable to mechanical. Eventually, the contacts welded and the relay was shot. Didn't matter at the time, because the relay was free and it was experimental, but if I were to do it again, I'd ditch the relay in favor of silicon.
I also should point out for those that don't immediately see the danger here... We're talking anywhere from 100-320VDC, which at the very least will be extremely painful, and EASILY translates into lethal. Stay away from all of the high voltage wiring and battery. The use of an interlock and a bleeder resistor is a must. You've been warned.
One other thing, while the chemistries are similar, zapping isn't nearly as effective on NiMH as it is on NiCd. The shorts readily return.
FWIW...
Steve