Technical questions on a potato battery!

Discussion in 'Fred's House of Pancakes' started by Skoorbmax, Nov 29, 2012.

  1. Skoorbmax

    Skoorbmax Senior Member

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    Strange thread, but after googling without success, here I go.

    Last night I created a potato battery with a 16D galvanized nail and a tiny piece of very high gauge copper wire. The voltage was .9V and apparently that voltage is dictated by the anode and cathode used. I shorted the battery and its current was so low it couldn't even warm the wire (I was not surprised, but as a demonstration I then did it with a 1.5AA and I WAS surprised at how hot it got instantly :)).

    Questions:

    1) I know to increase battery voltage I will have to run more potatoes in series. But I also want more amps. I therefore assume that to jack up the amperage of a given cell I need to increase the surface area of the anode (the nail) and cathode (copper wire). Should the surface area of these generally be the same? In my example last night the 16D nail was hundreds of times the surface area of the very high gauge copper wire and I am assuming that the load capacity of this battery would have been truly pathetic indeed because of that.

    2) Does potato size matter? Potato is just the electrolyte and separator--as long as there is enough material to separate the two and cover the surfaces of both electrodes, I assume a small potato chunk would be as effective as a full size potato, right?
     
  2. eagle33199

    eagle33199 Platinum Member

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    When you say high gauge, I assume you're talking about a wire with a very small diameter? (20 gauge wire is much smaller than 10 gauge wire!). Try using a smaller wire gauge. You can also hook up multiple potatoes in parallel to increase the overall current output.
     
  3. Skoorbmax

    Skoorbmax Senior Member

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    Yep, it was thin as a hair almost :)

    I think I saw some pretty decently priced copper flashing at home depot. That would work very well, if not in a potato then some salt water or something. And more galvanized nails. I think a few of these in series plus much larger surface areas should be good!
     
  4. qbee42

    qbee42 My other car is a boat

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    The voltage of the cell is determined by the electronegativity of the electrodes. The two different metals have differing electronegativity, so you realize the difference as the EMF or voltage. To get a higher voltage you need different electrodes or put cells in series as you suggested.

    The potato provides the electrolyte which allows electrons to move between the electrodes. It isn't critical assuming you have enough electrolyte to complete the cell. The spacing of the electrodes will change the internal resistance of the battery. Moving them farther apart will produce more resistance, which means the supplied voltage will drop more as current increases.

    For more current you need more electrode surface area. You can do this with larger electrodes or by combining cells in parallel. It's not important that the electrodes have equal surface area. The excess area is simply not used.

    Tom
     
  5. Skoorbmax

    Skoorbmax Senior Member

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    Thanks! I may move over to some salt water cells. It seems a common thing for some reason a lot of grown men on youtube have put together multi-cell salt-water batteries. I guess at some point in a person's life it occurs to them they need to build a battery and I'm at that point now.

    I need to find a great electrolyte. Vinegar and salt water seems common. I've read of bleach, but I don't know at what point the chlorine fumes become toxic. Perhaps at a level many times higher than I'd possibly end up using. Maybe aluminum foil and copper would work well, too.
     
  6. DavidA

    DavidA Prius owner since July 2009

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    Does the freshness of the potato matter? What about variety? Does a long sweet potato produce more current?
     
  7. CAlbertson

    CAlbertson Member

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    The trick with electrolyte is that it not corrode the other parts. Salt water, potatoes or a lemon all work but have practical differences.

    If yo want more current replace the wire electrodes with sheets of copper and steel. If you get two sheets of foil and place an insulator like fiber glass between them and then roll the assembly into a cylinder shape. Then place the assembly in liquid electrolyte. Now you should be able to get some real current
     
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