http://www.instructables.com/id/fix/step7/Zap-NiCad-Batteries-Back-to-Life/

Cobblers or has anyone tried it?
Sounds plausible but that probably means it's bogus

Whoever tries it first, can you please video it?

bit OTT but theorys not far away.
NiCads can be revived by flashing across a car battery charger for a second-ish for a single cell to 3-4 for a pack (NiCds are 1.2v/cell so 9.6v pack is 8 cells).
ideally the cell(s) should be discharged to 0v, a car bulb will do this. when discharged, then 'flash' them. they cannot be used at this point as the high rate flash really only brings the polarity back, so they will need a full charge via the normal method before use.
this doesnt work for cells that are checially knackered, but fine for batts that have been left unused for months/years at a time. they will never be as good as new, but often get 50-80% of their original capacity back.
best way to ensure good service life of any nicad battery pack is to use them and charge them regularly, often rarely used but near new batteries fail, when old hard-used packs soldier on for years!

Make sure you only do it with nicads, NiMh nickel metal hydride and Lithium polymer and lithium ion rechargables arent as forgiving as proper nicads and can fail/go back if ya not careful

CNH

[Edited on 3/3/10 by CNHSS1]

Not sure I would recommend (and I would not use a welder!) it but I seem to remember doing that in the past (RC cars) and it did work.. The crystal growth bit is true, if you keep the ni-cad fully charged (unlikely as the self discharge at such a rate) they remove the wiskers automatically...

Dan

[Edited on 3/3/10 by Bluemoon]

Switch to LiPo's

I've revived plenty of dead nicads using a bit of car battery abuse, but IME they are never the same again and have much higher self discharge from that point on.

I've always thought the best way was to fully cycle them a few times to get correct the memory effect. i.e. fully charge, fully discharge, fully charge, fully discharge....etc.

Haven't heard of the welder trick but wouldn't mind waching - from a distance.

I've tried it on a 12 volt NiCad which was dead. It showed a full charge after being on for a couple of minutes and had no power in it. Now it takes an hour to charge like it used to and will drive screws and drill but it doesn't last as long as it used to.