|Make Your Own Lemon Battery|
Creating a battery from a lemon is a common project in many
science text books. Successfully creating one of these devices is
not easy. Batteries consist of two different metals suspended in an
acidic solution. Copper and Zinc work well as the metals and the
citric acid content of a lemon will provide the acidic solution.
Batteries like this will not be able to run a motor or energize most
light bulbs. It is possible to produce a dim glow from an LED.
The lemon battery is called a voltaic battery, which
changes chemical energy into electrical energy.
The battery is made up of two different metals (the zinc nail and
the copper penny). These are called electrodes, which are the parts
of a battery where electric current enters or leaves the battery.
The electrodes are placed in a liquid containing an electrolyte,
which is a solution that can conduct electricity.
In a solution of water and an electrolyte, like the acid in the
lemon, an excess of electrons collects on one end of the electrodes.
At the same time, electrons are lost from the other electrode.
Touching the electrodes to your tongue closes the circuit and
allows an small electric current to flow. A single lemon produces
about 7/10 of a volt of electricity. If you connected two lemons
together, you can power an inexpensive digital watch (uses about 1.5
volts). (Use a length of thin, flexible wire to connect the silver
wire of one lemon to the copper wire of the other lemon. Then attach
thin wires from the other two wires in the lemons to where a
battery's positive and negative poles connect to power the watch.)
The tingle felt in your tongue and the metallic taste is due to
the movement of electrons through the saliva on your tongue.
The picture at the top of this page shows a basic lemon battery,
a lemon, copper penny and zinc coated nail.
The lemon: A large, fresh, "juicy" lemon works best. The nail:
Galvanized nails are coated in zinc. I used a 2" galvanized common
nail. The penny: Any copper coin will work. (Canadian pennies from
1960 - 2001 all worked)
Creating the battery: Insert a penny into a cut on one side of
the lemon. Push a galvanized nail into the other side of the lemon.
The nail and penny must not touch.
This is a single cell of a battery. The zinc nail and the copper
penny are called electrodes. The lemon juice is called electrolyte.
All batteries have a "+" and "-" terminal. Electric current is a
flow of atomic particles called electrons. Certain materials ,
called conductors, allow electrons to flow through them. Most metals
(copper, iron) are good conductors of electricity. Electrons will
flow from the "-" electrode of a battery, through a conductor,
towards the "+" electrode of a battery. Volts (voltage) is a measure
of the force moving the electrons. (High voltage is dangerous!)
I have connected a volt meter to our single cell lemon battery.
The meter tells us this lemon battery is creating a voltage of 0.906
volts. Unfortunately this battery will not produce enough current
(flowing electrons) to light a bulb.
To solve this problem we can combine battery cells to create
higher voltages. Building more lemon batteries and connecting them
with a metal wire from "+" to "-" adds the voltage from each cell.
The two lemon batteries above, combine to produce a voltage of
1.788 volts. This combination still does not create enough current
to light a small bulb. Note the red wire connecting the batteries is
joined from "+" (penny) to "-" (galvanized nail).
Four lemon batteries create a voltage of 3.50 volts. We should be
able to light up a small device like an LED (Light Emitting Diode).
Note the connecting wires go from "+" to "-" on each battery.
To turn on an LED you must determine the "+" and "-" connections.
If you look closely at the red plastic base of an LED you will
notice a "flat" spot (indicated by arrow above). The wire that comes
out beside the flat spot must connect to the "-" side of a battery,
the other wire to the "+" side.
Important information about LEDs: LEDs are designed to work at
very low voltages (~ 2V) and low currents. They will be damaged if
connected to batteries rated at over 2 volts. LEDs require resistors
to control current when used with batteries rated at over 2 volts.
Lemon batteries produce low current. It is OK to connect an LED to a
In the above image, electrons flow from the "-" (nail) end of our
lemon battery through the LED (making it glow) then back to the "+"
(penny) end of the battery. This is an electronic circuit. The LED
glows dimly with this configuration.
Improving your battery. The quality of the copper and zinc can be
a problem for a battery like this. Pennies in particular are rarely
pure copper. Try substituting a length of 14 gauge copper wire
(common house wire) for the penny. Experiment with different lengths
and configurations of electrodes. Other sources of zinc and copper
may be found in the plumbing supply department of a hardware store.