Potato battery


In 1799, Alessandro Volta made the first electric battery.



(1)

In the paper lunch bag with the green tape you will find:
  • A potato, which you should cut into 4
  • Small spikes, 4 each, of different metals:
    • copper
    • steel
    • aluminum
    • zinc
  • Wires or alligator clip leads
  • One or more LEDs


(2)

A 'battery' can be made from any two different metals (or non-metal conductors) and an electrolyte, usually an acidic liquid. The potato is weakly acidic, and you can also use lemons, oranges, water melon, vinegar etc.

In the picture, you can see 4 copper-zinc-potato batteries.



(3)

But first let's see what different combinations of metals can do. Stick different metals, one pair at a time, into the potato, and measure the voltage. There are 6 different unique combinations (marked with '?'.

Which combination gives the highest voltage?

Voltmeter cheat sheet 

           copper  steel   aluminum   zinc
          -------+-------+----------+------  
  copper     -   |   ?   |    ?     |    ? 
  steel      -   |   -   |    ?     |    ? 
  aluminum   -   |   -   |    -     |    ? 
  zinc       -   |   -   |    -     |    -


(4)

What does it take to light up an LED? AN LED takes a few volts before it will turn on, so one potato battery will not do it.

You can add voltages by connecting batteries in series. Here you can see the two right copper-zinc batteries are connected, that is, the zinc of the first is connected to the copper of the second. Wrap wires tight to make a good contact (sometimes cleaning the surface, in particular of the zinc nails, with the little piece of sandpaper)

Two potatos, still not enough

 



(5)

Four cells lights up the LED!

Going counterclockwise from the LED, you see the long leg of the LED goes to the copper leg of the 1st cell, then zinc connected to copper of the second cell, and twice more until the green wire from the last cell goes to the short leg of the LED.



(6)

Currently, battery research is hot stuff. Researchers are looking for:
  • Small, lightweight, long-lasting batteries for mobile devices
  • Very large batteries for storage of solar and wind power (weight is not a problem here)
  • Big, lightweight batteries for electric cars and trucks
  • How about airplanes?
Hubert van Hecke
Last modified: Tue Jun 9 00:50:41 MDT 2020