Expert: Mike Fulcher - 9/19/2008

Question
QUESTION: Mark,
I am trying to re-create a Zamboni battery. I am using Manganese dioxide and tin (just like Zamboni in the 1800's). I am making the individual cells out of a layer of Tin, paper (soaked in Zinc sulphate) and Manganese dioxide. I mix the zinc sulphate and manganese and starch together and paint it onto the paper. I let it dry and then cut it into small squares.
The reason I am seeking your counsel is that I am having a hard time with the resultant voltage. Each cell starts out at about .6 of a volt. The problem is the voltage seems to vanish very quickly. If you measure the voltage for 30 seconds, it has almost gone to zero. Since these batteries are capable of lasting for over a hundred years (see the Clarendon battery at Oxford), My cells seem to be lacking something.  

My question is: What would the proper instrument be to measure the voltage? A voltmeter seems to destroy the cells very quickly. A single cell won't budge an electroscope.
Second question: Do you see some stupid mistake that I am miking in my construction?

Thank You,
Paul Prado

ANSWER: Paul

At first guess I would say that the behavior you're seeing may be related to the type of paper you are using for the battery separator.  The presence of voltage followed by it's disappearance suggests to me that there is shorting between the two electrodes through the paper.  Try using two sheets of paper between the electrode sandwich and see if that affects the rate of voltage drop.  If that doesn't work, more detailed observations will be necessary.

A standard voltmeter should have a large enough internal resistance as to not appreciably affect the cell voltage via discharge.  Typical values are on the order of 100s of megaOhms.

I hope this helps you.

---------- FOLLOW-UP ----------

QUESTION: I tried putting a second piece of paper between the cells. When I did that, no voltage at all is present.

I have many small squares of the existing sandwich material (Alum. foil+Manganeese dioxide) stacked together. The voltages should add together, I.E. .4+.4+.4=1.2. When I stack a hundred together, the voltage is only a volt or 2.
Can you think of any reason that the voltage of 100 of them is not around 40 volts? That is my central problem, as the goal is to get around 1KV.

Thank you very much for your consideration. I know this is not a "normal" question. If you know of anybody who has actually built on of these, who might be willing to assist, please feel free to send me the e-mail address. I have been trying for a few months now and, as I'm sure you can see, am quite frustrated.

Again, Thank you very much.
Paul Prado

ANSWER: Paul

Theoretical voltages are typically higher than actual measured voltages because of polarization potentials caused when you draw the small amount of current necessary for measurement.  Your low voltage observation suggests there's an issue somewhere within your construction.  Could you give me some more detail on your construction?  Layer by layer for the individual cells, as well as your stacking configuration.  With that info I'll try and see if i can figure out what's going on.

---------- FOLLOW-UP ----------

QUESTION: I have tried several different configurations that all failed to achieve "stackability" in the voltage department.
That is to say that the voltage does not seem to increase, but remains the same no matter how many I put together. I have noticed that a stack of about 5 cells shows voltage increase for each cells that I added, but stacking 100 reverts back to a volt or 2.

My most successful recipe is
Recipe #1, which is:
MN=Manganeese Dioxide
ZS=Zinc Sulphate
FM= Aluminum Foil backed paper (used to wrap candy)
S=Starch (liquid)

I mixed 2 cap fulls of starch with 2 tsp of ZS and 1 shot glass of water and 2 TSP of MN.
I mixed that together and "painted" it onto the FM paper using a foam painbrush. I then waited for it to dry and cut it into 3/4 inch squares.
The cells will measure about .4 volts each.
When I stack them together Approx 200 squares), I put them in a small clamp that looks like a small set of calipers. When I test the voltage, If I apply pressure to the clamp, it will read about 1.6 volts. As I am taking the reading, The voltage will quickly drop by hundredths of a volt per second.

I have found, as Zamboni found, humidity plays a large role in the cell. If I leave the lightly clamped cells out in Florida humidity overnight, the voltage starts out much higher, maybe 3.6 volts, but shrinks equally quickly as I measure it.

I have also tried using graphite instead of MN, it is not as high a yield.

I also tried using just regular paper, and painting on the MN+ZS+S mixture. Then cutting it out into squares. I then cut many tin squares and had the same falling voltage result and lack of voltage "stackability".
Any help you can render will certainly be appreciated.

Thanks,
Paul Prado

Answer
Now for more questions.
Which side of the paper do you paint on?  My guess would be the paper side, not the foil side right?

After painting on the non-foil side you've got a manganese dioxide - aluminum cell with paper as the separator.  Sounds straightforward enough.

When you stack the cells, how do you stack them?  Do you stack aluminum to aluminum and then MnO2 to MnO2?  Or do you stack aluminum to MnO2?  This would be the preferred way, but it's important to separate each cell a piece of metal foil if you do this.  Otherwise no matter how many cells you stack you'll still get the voltage of only one cell.  This would also give you a rapidly decaying voltage as the cells react.  The foil is intended to prevent electrolyte leakage via diffusion but still allow the cells to be electrically connected.  If you haven't already, give this a try and let me know how it goes.