FIGURE 4. Disassembled NiCad.
1. Cathode plate. 2. Separator.
3. Anode plate.
homebrewed cell was to literally
use a conductive glue to attach the
oxides to the outside of the
electrodes. This gives a very high
surface area “sandpaper” like finish
to the electrodes, which is exactly
what we want.
The electrodes themselves
need to be nickel, or nickel plated.
It’s very important to remember in
your own designs that virtually any
material other than nickel will
corrode rapidly in this type of cell
under the electrical action. If you’d
like to do your own nickel plating,
Sources are included here.
Your plate size can be
anywhere from 10 cm square to a
little over 50 cm square and still fit easily in a mason jar.
It is certainly possible to greatly increase this size with
multiple plates or even a standard “jelly roll” battery
construction. Figure 4 shows this jelly roll construction of
a NiCad battery.
Of course, your plates must not touch each other in
the cell, so you may need to use a permeable nonconductive separator. This is actually a big topic, but for
an experimental cell, it’s possible to use layers of fiberglass
screen (available at any hardware store).
For my own simple cells (pictured), I soldered some
solid copper wire to a fine copper screen (I think copper
foil or plate would work, as well). I coated the solder
connection with epoxy, and then nickel plated the screen.
Next, I simply coated the screen with a very
thin layer of conductive epoxy (it goes a VERY
long way if spread thin). (Conductive epoxy can
be found in both nickel bearing and silver
Last, I sprinkled and pressed powdered nickel
oxide into the wet glue for my positive plate, and
iron oxide for my negative plate. The results can
be seen in Figure 5.
Though I’m not certain what the actual
longevity of using epoxy to hold oxides to the
plates will be, my test cells are now more than a
year old and have been charged daily from solar
cells without problems. So, mark this method as
seems to work but, of course, is still experimental.
Begin by mixing a 20% solution (by weight) of
potassium hydroxide and distilled water in a pyrex beaker.
Keep in mind while doing so that potassium hydroxide
should be added slowly to the water; never the other way
around. Potassium hydroxide will react exothermically and
some heat will be generated.
Gloves and goggles should always be used, and
FIGURE 5. Homemade plate.
February 2012 41