One Potato - Two Potato

Do you know that you can run a clock using potatoes as the battery.

You can find commercial sources for a "potato clock" online ($19.95 + shipping).

But it's more fun to build one from "Scratch".

Step 1

Assemble your supplies. You'll need two common galvanized nails; three alligator clip/wire units - that is, alligator clips connected to one another with wire; two short pieces of heavy copper wire; a simple low-voltage LED clock unit; and two potatoes. Obtain a simple LED clock unit that functions from the power of one AA battery.

Step 2

Open the battery compartment and remove the battery.

Step 3

Note that there is a positive (+) and a negative (-) terminal point where the battery was installed.

Step 4

Identify the potatoes as number one and number two.

Step 5

Insert one nail in each potato.

Step 6

Insert one short piece of heavy copper wire in each potato, placing it as far from the nail as possible.

Step 7

Use one alligator clip/wire to connect the copper wire inserted in potato one to the positive terminal in the clock unit.

Step 8

Use one alligator clip/wire to link the nail in potato two to the negative terminal in the clock unit.

Step 9

Use the final alligator clip/wire to link the nail in potato one to the copper wire in potato two.

Step 10

Set your clock.

How it Works

An electrochemical battery stores chemical energy that changes into electrical energy that runs electronic equipment. There is a chemical reaction within the potato battery that causes the electrons to move. The electromotive force within each potato is the ability it carries to move electric current. In an electrochemical cell, such as the potato battery, the copper wire makes the electrons move in the potato, causing energy to move into the clock.
The official scientific name for the chemical reaction is "redox reaction." The process starts when one side of the battery loses electrons. This happens in the the zinc nail, which forms the anode, or positive part of the circuit. The zinc in the nail reacts with phosphoric acid in the potato, releasing electrons. The zinc anode loses 2 electrons while the copper in the wire reacts with the phosphoric acid to release hydrogen ions, which gain the electrons. This is the negative half of the circuit, or the cathode, which thereby gains the electrons.

I measured the voltage of my potato battery, with a voltage meter, at about 1.1 volts. This is sufficient voltage to substitute for the AA battery (typically 1.25 volts).

You should be able to power the same clock with a couple of lemons, bananas, apples or avocados, as well as pickles and some soft drinks (mostly of the sugared variety).

This link gives a good description of "Potato Power"

When you finish with your project, do not eat the potatoes.