the cell because the cell reaches full charge before the
negative electrode reaches capacity.
An Experimental Cell
FIGURE 2. Anode cut-away
An experimental cell can be easily constructed on
your workbench, and many of the cell’s characteristics can
be seen and measured first hand. In fact, for a very simple
science fair type project a 10 cm square plate of nickel
screen and a similar plate of iron will have enough oxides
naturally on them after a few charge cycles to light a low
power LED for about 12 minutes when charged (Figure 3).
Though such a cell has a minute capacity, it’s still
interesting as a proof of concept experiment, and it
recharges very rapidly making a nice science fair display.
It’s also very interesting that an ultra simple cell of this
kind may well have an indefinite lifespan. This might be
useful for a millennium project in
conjunction with a solar cell for
maintaining an ultra low drain
memory circuit or some such thing
for decades. However, for an
interesting and useful project for
Nuts & Volts, we want to get more
capacity in our cell than that!
For that, you’ll need to procure
a small quantity of both nickel II
hydroxide and the iron oxide (Fe3
O4), as well as some powdered
potassium hydroxide (KOH) for
your electrolyte. Chemical supply
houses will stock these items.
As an alternative source, I’ve
also found pottery supply houses
use oxides of both nickel and iron
as colorants in pottery, and are far
less expensive than chemical
suppliers (see Sources).
eBay is an excellent source for
potassium hydroxide because it’s
currently used in making
homemade bio diesel and
soap.Important note: I have
successfully used nickel III oxide
instead of nickel II hydroxide for my
positive electrode with excellent
results. It’s cheaper, seems to work
better, and is much easier to find.
A simple idea I had for
increasing capacity in our
FIGURE 3A. LED run from
FiGURE 3B. Plates and
separator from the
battery shown in