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 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 lemon battery.







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.



The first battery was created in 1799 by Alessandro Volta . Today
batteries provide the power for an amazing variety of devices,
everything from flashlights to robots, computers, satellites and cars.
Inventors and researchers continue to improve the battery, designing
batteries that last longer and that are more friendly to our
environment.



Understanding how batteries actually work requires a knowledge of
chemistry. The most important factor in battery design is the
electrical relationship between the two metals used in the battery.
Some metals give electrons away while other metals accept extra
electrons. Chemists have investigated metals and created an "electric
potential" table comparing different metals.