Some people claim to recover dead NiCd batteries – i.e. batteries showing 0 V on a voltmeter and that doesn’t revive by hooking them to a charger – by performing a high-current quick charge, process known as “zapping”, and them putting them back to the charger for a regular charge.

In fact, this will work if the battery has an internal short circuit caused by a small dendrite, which is a small piece of material connecting the two battery poles internally. What the zapping does is to burn this dendrite, like if it were a fuse, solving the short-circuit problem.

But the problem can come back, because not only other dendrites can be formed but also the material that was vaporized is now inside the battery, which can act as a resistor, making the battery to hold less charge than when it was good.

However, zapping the battery if the problem isn’t an internal short circuit can damage the battery even more. As we mentioned, if you let your NiCd battery completely discharged, it can be damaged – i.e. completely discharged forever – and the problem here won’t be any dendrite inside creating an internal short-circuit.

Keep in mind that this technique has nothing to do with “memory effect”. Some people can claim that they solved the “memory effect” of a battery by doing this but in fact the battery problem was another one (internal short circuit).