Vol. DIY Electronics Projects

Chapter 3 DC Circuit Projects

DC Lab - Potato Battery

In this hands-on electronics experiment, you will create a battery from a potato (yes! a potato) and learn about the relationship between chemical energy and electric energy.

Project Overview

In this project, you will build a battery using a potato, a zinc electrode, and a copper electrode. You will measure the voltage with a voltmeter and investigate how the voltage is related to the electrode spacing and surface area (Figure 1).

Building a potato battery and measuring the voltage

Figure 1. Constructing a potato battery and measuring the voltage.

How does a potato battery work? The zinc (on the surface of the galvanized nail or screw) and copper (in the penny or wire) react together to produce chemical energy. The potato acts as an electrolyte between these two dissimilar metals. This chemical energy is then converted to electric energy as the current flows through the circuit.

Parts and Materials

One large potato
A strip of zinc, or galvanized metal nail or screw
A piece of thick copper wire and/or a copper penny

This basic experiment is based on the use of a potato, however, many fruits (lemons and limes, for example) and vegetables can also work as potential batteries! For the zinc electrode, a large galvanized nail or screw works well. Nails with a thick, rough zinc texture are preferable to galvanized nails that are smooth.

Learning Objectives

To determine the importance of chemical activity in battery operation
To determine how electrode surface area affects battery operation

Instructions

Step 1: Push both the nail and the wire deep into the potato, as illustrated above in Figure 1. Measure the voltage output by the potato battery with a voltmeter. Now, wasn’t that easy?

Step 2: Seriously, though, experiment with different metals, electrode depths, and electrode spacings to obtain the greatest voltage possible from the potato. Try increasing the copper surface area by wrapping the wire around a copper penny.

Step 3: Try other vegetables or fruits and compare voltage output with the same electrode metals.

It can be difficult to power a load with a single “potato” battery, so don’t expect to light up an incandescent lamp, power a hobby motor, or do anything like that. Even if the voltage output is adequate, a potato battery has a fairly high internal resistance which causes its voltage to “sag” badly under even a light load. With multiple potato batteries connected in series, parallel, or series-parallel arrangement, though, it is possible to obtain enough voltage and current capacity to power a small load.