15 Nov
2002
15 Nov
'02
8:24 a.m.
At 09:05 AM 11/15/02 -0600, Gary wrote:
Lawrence Walker wrote:
I have used an automobile battery to "zap" them. Shorting a NiCad to an auto
battery for just a split second usually burns out the whiskers. HOEVER the fix usually
doesn't last long. One of things that happens when the whiskers grow and short the
electrodes is that they also pucture the membrane that separates the electrodes. Once that
happens, the battery doesn't last long. ALSO zapping NiCads can can over-pressure and
rupture the vent and possible spray out electrolyte (potassium hydroxide solution) if get
them too hot. Not only is this an immediate hazard but it can also cause slow leaks that
go unnoticed until the electrolyte eats up the circuits in the device that the batteries
are installed in.
I'm not saying not to zap your batteries. Zapping them is a great way to get them
working again FOR A SHORT TERM. That will at least let you test the device to see if it
works before investing money in new batteries. However just be aware of the dangers of
zapping and DON'T leave the batteries in the device after you're done testing it.
Joe
This has come up before but I can't remember it being resolved.
I often see suggestions for rejuvenating failed or dying laptop batteries using
a hi-amp source to flash them and break down the built-up crystals.
What really happens is that minute 'hairs' grow from terminal to
terminal in the cell, effectively shorting it out. To remove them
requires a flash of current to 'burn' them out. Either a high current
source (10A or more) or a large capacitor discharged into the cell does
the job.