|Re: Care and Feeding of Topcat NiCads|
Message #9 Posted by Les Wright on 1 June 2012, 1:27 a.m.,
in response to message #8 by Katie Wasserman
I was a bit spooked at the idea at first, so I looked for a reportedly effective method that seemed to be relatively safe and didn't require a car battery or arc welder, both of which scare me a bit.
The most approachable method (for power drill packs) entailed hooking up two or three health packs in series, attaching the dead pack to the series negative to negative, and "zap" by repeatedly taping the positive lead to the positive terminal of the dead battery rapidly for a few seconds, letting things cool, then charging normally.
My variant entailed a 16V, 4A power adapter for a Duracell rapid charger (which basically destroyed a few NiMH cells before I clued in that faster was not better). The negative terminal is the outside of the barrel of the plug, so I wrapped the negative lead around and taped in place. I taped my wire leads, neg to neg and pos to pos, onto the terminals on the pack. I then twisted the wire of the positive lead to a fine point and did the rapid tapping thing by moving the wire end in and out of the barrel of the plug. I only did this for a few seconds--the wires got warm in my hands and the battery warm to the touch quite quickly. I let the packs cool and I have been charging them and using them normally since.
I have seen variations involving harvesting capacitors from disposable cameras, and I am sure they work great in tougher cases that need a bigger zap. But judging from how warm my packs got, and so quickly, I could help but think that I was dealing with some significant current for the job at hand.