Nuts and Volts - February 2012

Nickel Flake Nickel II Hydroxide

the cell because the cell reaches full charge before the negative electrode reaches capacity.

An Experimental Cell

FIGURE 2. Anode cut-away showing layers.

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.