On Mon, 7 Jul 2014 00:02:34 -0700 (PDT),
wrote:

I used to read a lot of electronics experimenters books when I
was a kid, (way back).

I grew up on a steady diet of Popular Electronics and Carl and Jerry
stories.
http://www.copperwood.com/carlandjerry.htm
Actually, I never really grew up, but we won't go there.

Some of this reminds me of an experiment I once performed. I
took a standard carbon zinc D cell that was dead and soldered
two wires, that were connected to a flashlight bulb onto it.
I then punched numerous holes in the battery and immersed
this contraption into a solution of very salty water. After
a few seconds the lamp began to glow.

About fifteen years ago my youngest boy needed an experiment
for Science class and I suggested this one, which we named
the "Frankenstein battery". It apparently was a big hit at school.
Lenny

Nicely done. I took apart a carbon-zinc alarm battery, and recreated
the battery in a mason jar using vinegar and lemon juice as
electrolytes. That worked, but made a huge mess in the kitchen. My
father moved me to the garage, where I recreated the mess.
Lesson learned: The bigger the mess, the better it works.

Some years later, I was pondering if there was something that could be
done to revive expensive dead NiCd batteries. I knew that
overcharging and overheating NiCd batteries would cause them to
"vent". My guess(tm) was that there was some electrolyte loss
involved. So, I notched a corner of the cell with a triangular file,
and used a syringe to inject some KOH (potassium hydroxide)
electrolyte. That worked in about half the cells I tried, but I was
only able to obtain about half the original ma-hr capacity. Had I had
been able to inject the KOH under pressure, to better distribute it, I
might have done better. Later, I increased the KOH concentration from
about 20% to 100% KOH and created yet another smoking mess.
Lesson learned: A bigger mess does not make a better battery.

Roll forward many years, and I'm still experimenting with NiCd
batteries. This time, I want to see how quickly a NiCd can be
charged. I now had more test equipment and a source of cheap cells. I
would charge the cell from about 10% capacity, to as close to 100% as
possible, as quickly as possible, and then test for capacity using a
West Mtn Radio CBA-II battery analyzer.

NiCd batteries do not get warm until they are overcharged. It is
possible to charge a depleted battery at almost any charge rate
imaginable, as long as it is not overcharged. Overshoot even
slightly, and the battery will overheat and possibly explode. The
threshold is amazingly sharp and varies with battery vendor, age,
condition, past history of battery abuse, and the position of the
moon. In short, it wasn't very predictable. I would successfully
charge a collection of batteries at a 10C rate but eventually find one
battery that would explode without warning or reason. My very fast
charger was not going to be a very safe commercial product.
Lesson learned: A big mess is a good indication that the idea is not
commercially viable.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558