The Lost (almost) Technology of the Edison Cell

With the wild fluctuations in fuel prices over the last few years, world concern over global warming, and simply the idea of creating new and more sustainable technologies, immense interest and progress has developed recently in the world of battery development.

In fact, it seems that every day we hear of a new breakthrough, and another step closer to that long sought elusive goal of a truly workable battery storage system!

Perhaps one day soon we’ll have a battery that displays no “memory” effect, one that can be completely discharged or overcharged without harm, and require no complex computerized management system. This battery could even prove so durable it will be immune to damage from vibration and not break down chemically over time. In operation such a battery might even routinely outlast the very vehicle or machine it was designed to operate in!

Like many overlooked gems throughout the history of engineering, perhaps these “diamonds in the rough” deserve a second look, and some thoughts as to how our present technology could be improved by examining the principles of their operation.

Many times historically these cells have been referred to as “the battery that worked too well.” Though they were popular and profitable in niche markets for Edison, it has been said that a business model could never be created for the general public by producing a product that does not require replacement!

However, in our new age where “going green” is more than a quaint idea, but looks every day more like a necessity, perhaps Edison’s idea has finally truly found its time?

Principles of Construction

In many ways, the remarkable “Edison cell” is the opposite of the batteries we use today functionally.

Edison used simple Iron (anode) and Nickel (cathode) screens for the electrodes submerged in a potassium hydroxide electrolyte. Next, he bucked the popular methodology and rather than a strong acid, the Edison cell used an alkaline electrolyte (potassium hydroxide)
for his cell.

The basic chemical reaction can be written as shown in Equation 1.

0908_F6_eq1

An alkaline electrolyte proved to be not only effective, but unlike acid, the solutions was protective of the metal electrodes in the battery giving them their phenomenal lifespan.

The alkaline solution was also safer than acid, being about the same toxicity as ordinary bleach. (The raw chemical potassium hydroxide is not so benign and must be handled carefully as we’ll see later in an experimental cell.)

Edison claimed that he would not begin actual manufacturing of the cells unless he achieved 5 times the capacity of the competing (lead acid) cell.
At one point, he claimed to have reached 15 times the energy density of lead acid in a series of remarkable experiments.

Edison had found the cell’s capacity increased directly with the surface area of the plates. Because the electrolyte is protective of the plates, Edison learned that he could create exceedingly thin plates of nickel and achieve exceptionably high storage capacities.

At one point, he electroplated alternating coverings of nickel and copper on to a cylindrical form, then dissolved the copper leaving atomically thin layers of nickel for a spectacular surface area/energy density.

Though the process was claimed to be successful, the manufacturing of such forms proved too expensive to be commercially successful in Edison’s day.

Edison did however, move ahead with cells he claimed to be several times the capacity of lead acid cells. Some of which are still in service today.

It’s hard not to wonder with today’s astounding capabilities in miniaturization, and nano machines a what might be possible for plate creation with such robust cells.

An Experimental Cell

An experimental cell can be easily constructed on a workbench, and many of the cell’s characteristics can be seen and measured first hand.

I want to say up front that the cell I’m about to describe is in no way efficient or optimal in construction. It should be considered at best a simple test device for datalogging the charge and discharge reaction described, and for perhaps experimenting with alternate configurations you might have in mind!

I do have to admit, the idea struck me in creating this little cell that a novel project for IN Compliance might be to convert one of the solar garden lights in the yard to a “50 year garden light” using an experimental cell. However, with the small active surface area of the plates in the described cell, my garden light only lights for 12 minutes per evening so far… So that project will remain “in the works” while I contemplate greater surface areas.

I also want to briefly say that you must evaluate your own skills in handling chemicals and electricity if you decide to attempt construction of an experimental cell. I do not claim to be an expert in battery construction, nor to know or present all the potential dangers that could be involved in constructing a cell.

Construction is straight forward.

Begin by mixing a 20% solution 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, and never the other way around.

Potassium hydroxide will react exothermically and some heat will be generated.

Gloves and goggles should be used always, and the raw potassium should be handled carefully.

The experimental cell uses a simple nickel and iron plate each approximately 2” X 4” as shown in Figure 1.

 

0908_F6_fig1

Figure 1: The experimental cell uses a simple nickel and iron plate each approximately 2” X 4”

 

The plates are connected by wires to a pair of binding posts (such as Radio Shack 274-662), which are mounted in the lid of a one pint Mason jar as shown in Figure 2.

 

 

0908_F6_fig2

Figure 2: The plates are connected by wires to a pair of binding posts which are mounted in the lid of a one pint Mason jar

The perfboard serves as an insulator between the plates, and epoxy covers the point where the wire is connected to the plate as seen.

Fill the mason jar with the potassium hydroxide solution, keeping the level well below the point at which the wire connects to the plate, and screw the lid on the jar.

Your cell is ready for charging!

Edison recommends charging your cells with a voltage 1.85 times the number of cells you are charging in series.

Your cell will improve each time you charge/discharge it.

Your cells take on a charge very slowly, especially at first. Limiting current to 50 milliamps or less is recommended, though Edison says larger currents are fine as long as the electrolyte does not “froth” or exceed 115 degrees.

Some gassing at the terminals is normal, and harmless. If liquid levels begin to get low in the cell, add distilled water only.

Remember that increasing the electrode’s surface area will greatly improve your cell. For this reason, nickel and iron screen would be much preferable to plates if you can find them.

Figure 3 shows an LED powered from experimental cells through a 500 ohm resistor. These cells have only had a couple chargings, but powered the led for about 12 minutes.

 

0908_F6_fig3

Figure 3: An LED powered from experimental cells through a 500 ohm resistor

 

Final Thoughts

Surprisingly, my first introduction to Edison cells was at a local energy fair almost 15 years ago. A professor from a junior college exhibited a Volkswagon converted to run on a large set of antique Edison cells. The cells in his car, many more than 50 years old, had been operating his Volkswagon with off shelf motor and other components throughout the school year. He claimed a range of nearly 100 miles, and a top speed of 60 MPH.

I hope you find old technology and what might be technical “diamonds in the rough” as intriguing as I do.

New batteries may well soon eclipse what has been done in the past, but sometimes older technology can surprise you! favicon

For additional information, (including a video showing the construction of the cell), visit www.noonco.com/edison.

For more information about Walt Noon, please visit www.noonco.com.

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