Homebrew Battery and Electrostatic Generator
For many years, before batteries were mass produced, electrical experimenters had to make their own batteries and many concoctions were tried. You "can" try this at home yourself with materials commonly found around the house.
Recipe for Making a DIY Battery
- 1 Lemon or lime
- 1 Galvanised roofing nail or galvanised screw
- 1 Piece of heavy copper wire (Mains cable without the insulation) or a shiny copper coin.
Checking the Ingredients (Optional)
You could try the old fashioned "Tongue Test" (First make sure the parts are clean. See 2 below)
As with wine tasting: Taste - Don't swallow.
(Note: This is an experiment in electronics, not electric cooking. We recommend that you do not eat the fruit used in your battery)
- Squeeze the lemon gently without breaking the peel to release the juices inside.
- Thoroughly clean the nail and the copper wire until they are bright. Use steel wool if necessary and rinse well in water.
- Insert the nail and the copper wire deeply into two separate points on the lemon taking care that the wire does not touch the nail.
- Check the potential between your two improvised skewers with the voltmeter.
About half a Volt
Hungry for Power?
Don't expect to start your car with this battery - The internal resistance is rather high.
By connecting 3 or 4 batteries in series however you should be able to light up an LED (Light Emitting Diode) or a small flashlight.
The lemon may be replaced by other fruits or vegetables. You could try an Electric Potato for starters. The electric effect is the same.
Using a paper clip instead of the nail reduces the output to one third of a Volt.
If you can't find a galvanised nail, an alternative (and better) source of zinc is to cut a strip from the case of an old flashlight zinc carbon battery (D Cell).
The lemon acts as a battery case holding the lemon juice (citric acid) which acts as the electrolyte. The copper Penny is the Positive electrode and the zinc galvanised coating on the Nail is the Negative electrode.
A series connection is a chain of cells, the positive electrode of each cell connected to the negative electrode of the next cell, to form a battery of higher voltage.
A passable replica of Volta's pile can be constructed from a stack of alternately placed copper and nickel coins separated by discs cut from a paper towel and soaked in lemon juice or vinegar.
Make sure the surfaces of the coins are not oxidised)
For an explanation of how batteries work, see Battery Chemistries.
Kelvin's Thunderstorm is an amazing water powered electrostatic generator, which can be made from simple materials at home or school, capable of generating a potential of tens of thousands of volts at its terminals. It was invented by Lord Kelvin (William Thomson) in 1867 and has no moving parts, depending on electrostatic induction and positive feedback for its operation. He called the device his water-dropping condenser.
When a charged object (the charger) such as a metal tube is placed near a water dropper or nozzle, an opposite electrostatic charge is induced on the dropper. As the water drips from the nozzle, each drop carries away a small amount of that charge. If the drops are collected in a metal container below, the container itself becomes charged with a polarity opposite from the charge on the charger by accumulating the charge carried away by all of the drops.
Kelvin's device used two parallel droppers operating with opposite polarities with the water containers connected electrically to the charger in the opposite dropper. As the charge builds up in the container it increases the charge on the charger in the other dropper which in turn induces more charge on the water dripping through it.
In this way, opposite charges build up on the two water containers until the electric field across a spark gap between the two containers is sufficient to breakdown the air, at which point a spark jumps across the gap, discharging the droppers.
The device can create a spark across a gap of one centimeter or more (about 0,5 inches) and since the dielectric breakdown in air occurs at an electric field strength of about 3 × 106 Volts per metre, the breakdown voltage will be about 30,000 Volts. The corresponding current passed by the spark however will be very small so that the device would not be practical as a power source. This is because the only source of the energy built up in the device is that created by the work that gravity does in pulling the charged drop from the dropper.
The energy in the spark is very small and not enough to be dangerous.
There is usually sufficient unbalanced charge between the droppers to start the charge build up but it can be kick started by applying a charge created by rubbing a balloon or piece of plastic material to one of the chargers.
The chargers can simply be made from a pair of tin cans with the tops and bottoms removed.
The water should remain as drops and should not be a free flowing current.
The two droppers should not touch each other and the only connection between them should be the two feedback wires which should be insulated (or at least separated) from each other.
See also Steam Electricity