Picture of Leyden Jar Array for Tesla Coils

A number of people have asked how I made the Leyden jar array used with the "Tabletop Tesla Coil." In this separate Instructable I offer a detailed explanation of how the battery was made and what it can do.

Historical footnote: Ben Franklin created the term "Leyden battery" to describe grouping a number of Leyden jars together. He made the analogy to a battery of cannons. More cannons=more boom, more Leyden jars=more zap.

Leyden jars are the oldest form of capacitor. Basically they capture and store electricity, releasing it for use by other components in he circuit. The Leyden jar was invented in 1744-45 by two men, working independently: Ewald von Kleist and Pieter van Musschenbroek. Their original version used a glass jar filled with water. Basically a capacitor consists of two conductive surfaces separated by a dielectric (an insulator). The early Leyden jar was a glass jar filled with a saline or acid solution. A metal terminal passed through the top of the jar into the water; the outside of the jar was coated with metal foil.

In 1899, Nikola Tesla used banks of liquid-filled mineral water jars as the capacitor array for his high voltage radio and power transmission experiments in Colorado Springs. Modern Tesla coil builders often use homemade capacitors in their projects, usually made from beer bottles, aluminum foil, and salt water. There are other kinds of homemade capacitors--glass plates sandwiched with layers of foil, rolled sheets of polyethylene and foil, etc. The trend among coilers seems to be away from homemade capacitors and using instead "MMCs," or Multiple-Mini-Capacitors. These are arrays of high voltage commercial capacitors arranged in series and parallel to give the desired capacitance and voltage rating. Problem is, high voltage capacitors can be expensive and hard to find. When you do find high voltage caps, they may not be suitable for Tesla coil use, as the high frequency pulsations of power through a Tesla circuit impose severe stress on the components.

Because I'm cheap and have a long standing interest in old-fashioned technology, I decided to develop a dry, non-liquid Leyden jar that would work with a Tesla coil. I wanted a capacitor made of easily obtained materials that was sturdy, effective, and cheap. What follows is the design I've come up with so far.

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dudes1 year ago

do you know the voltage rating of these caps? together or individually

Mr. Apol (author)  dudes1 year ago
The only method i had to determine the ballpark voltage rating was to charge them with DC (via a Wimshurst machine) and observing the size of the sparks when it arced over. I estimate they can withstand 100KV DC.

I saw your "Tesla's candlestick" ible', and your doorknob cap array. would you be willing to sell some to me? If not, where did you get them. Also, where did you get your NST?

Mr. Apol (author)  TheRealRocketBurns1 year ago
I can, if need be, or you can get them on eBay as I did. Look for a "doorknob capacitors" with a voltage rating at least double your NST and between 2000 and 3000 pico-farads (= 2-3 nano-farads).

I bought my NSTs on eBay as well, though you might try a shop that sells or services neon signs. Everyone's switching over to solid state GFI power today, and I hear shops want to get rid of their old iron-brick NSTs.

Hi, Mr. Apol

I am a fellow avid Tesla Coil maker that is just wondering if you at all used salt water in this, or are you just using the aluminum cans as your inner electrode / plate?

May just be me getting excited and reading too fast but thanks in advance.
Great job by the way - keep it up.

- Rosenberg
Mr. Apol (author)  TheAppleSauceMan2 years ago
There is no liquid in these. The soda can is in the inside electrode, and the foil tape is the external electrode. One advantage to this design (I hope) is that it doesn't contain heavy, sloppy salt water.

sara rarara3 years ago
lets say 40,000 v is enough but its difficult to find b/c new TV circuits doesn't fulfill requirement
sara rarara3 years ago
its now love for Tesla coil !!
sara rarara3 years ago
Good point! what would you suggest for replacing this 40,000 voltage old and difficult to repair b/c of old design and also difficult to find if fail.
sara rarara3 years ago
sorry for being unclear, English is my 2nd language that's why i have not enough vocabulary, i wanna replace existing TV circuit and fly back to modified Tesla coil, our purpose is to apply flock on sticky surfaced beads.
Mr. Apol (author)  sara rarara3 years ago
I'm not sure a Tesla coil is a good choice for electrostatic flocking. I don't know much about the process, but don't you need high voltage DC (direct current) for electrostatic coating? Tesla coils emit high frequency AC.

sara rarara3 years ago

i wanna build this capacitor for this high voltage coil.what would it mean there 10,000 volt?

actually i wanna renew the existing low voltage machine to high voltage,that's the machine use for fly very tiny particles of nylon (called flock) in the glass chamber electrolytically, the current machine is a TV circuit with fly back transformer.
Mr. Apol (author)  sara rarara3 years ago
I'm not at all clear on what you're wanting to do, but you must be very careful adding capacitors to a flyback transformer. Flybacks are already potentially lethal, and you're upping the output greatly by adding Leyden jars.

Is your purpose to apply flocking inside jars?

sara rarara3 years ago
can we use this for 10,000 capacitance and how?
Mr. Apol (author)  sara rarara3 years ago
I don't understand what you're asking--10,000 picofarads capacitance?

Each of these jars has a capacitance of about 500 pF. To get 10,000 pF you'd need about 20 jars.

rayfalcon5 years ago
Ok forgive my ignorance but you are saying that your setup puts out "100,000 VDC " how many amps is that equal to? Also have you tried using this setup to run anything yet? I'd love to find something like this that easily puts out 750 -950 constant cranking amps and a constant 12 VDC to start my mower with instead of wasting money on the ever price increasing "never ready " batteries from walmart. 
By the way could you also use this as a charger concept or a charge inductor for a regular or nominal battery?
Mr. Apol (author)  rayfalcon5 years ago
Leyden jars--which are simply capacitors--do not put out any more energy than is put into them. Leyden jars do not emit a stream of current, like a battery. They release pretty much all their charge in one go.

Also, don't confuse Voltage (http://en.wikipedia.org/wiki/Voltage) with Amperage (http://en.wikipedia.org/wiki/Amperage). When I charge the Leyden jars using a Wimshurst machine (see http://en.wikipedia.org/wiki/Wimshurst_machine) I am charging them with many thousands of volt DC at extremely low amperage. 100,000 volts at 7 microamps doesn't do much except create very large sparks. You're not going to start a mower or truck with power like that. If you did discharge 100k volts through an engine starting system, it would probably destroy every microchip or integrated circuit in it.

But if you reduce the voltage, the amperage will go up proportionally. Reducing 100,000 kV down to 12 at 7 uA would get you a lot more than 7 uA. At the same time, however, you are right in that you couldn't use it as a battery. Caps are meant for instant discharge, not steady current, that's why their application is in railguns, coils, and such, while batteries are used in a mower.
mark25023 years ago
Would any container work so long as its a tight fit?
because i was thinking of making them out of plastic bottles or styrofoam. also would any can, like a soup can work instead of a soda can?
also do these get hot? just out of curiosity
Mr. Apol (author)  mark25023 years ago
I think styrofoam would be too porous--the charges would leak through. Other plastics will work, but steel cans would be inferior to aluminum, partly because steel cans tend to be corrugated, which does not give tight contact with the dielectric outer container, plus thin aluminum tends to hold more charge than thicker metal would.

None of my Leyden jars have ever gotten hot. The wax on top would melt before the plastic, giving warning, and that has never happened. I have run these jars up to 60 mA without problem. High amperage, like from an MOT stack, might cause heat build up though.

Adrenal1ne3 years ago
Completely stupid Question: I am assembling a battery out of 8 oz leyden jars i already have, and i am trying to figure what this line means.. "crease them in the middle with the foil on the inside; this makes a V. Peel off the tape and careful spread the tape V over two of the Leyden jars. They should be close, but they don't have to be too rigidly joined.".
Where does the V go? Around the outside? On the tops? Can someone help?
Mr. Apol (author)  Adrenal1ne3 years ago
Not a stupid question at all--I apologize for not being clearer.

Basically, you need to link the outside coatings of all the Leyden jars in order to join them in parallel.

In the Instructable, I linked the polypropylene canisters with strips of metal foil tape. With the backing still on, folded a one inch wide, six inch long strip of tape in half the short way. When you peel the backing off, this will make a neat way to link the outside coating of one Leyden jar to the next. You can use wire, or strips of foil, etc. What's important is the outside coatings of the jars be electrically joined together.

Thanks. Do all the jars have to be linked to the adjacent ones, or is it just the outside?

Mr. Apol (author)  Adrenal1ne3 years ago
Yes, all the outside coatings should be linked by strips of metal tape, as all the inside electrodes--the soda cans--are linked by wire. Thus all the Leyden jars are linked in parallel; all negative electrodes together, all positives together.

Kalace3 years ago
Great thinking and work, for using leyden jars for tesla coil caps, i will have to try these out some time.
Mr. Apol (author)  Kalace3 years ago
Let us know if you build some of these.

jj.inc4 years ago
So it is just empty air space, not salt water or anything.
no he uses a aluminium can instead of salt water. because the salt water acts as the inside electrode. instead he just uses plain metal as it is a better conductor.
Thanks, I finally figured out that it is the walls of the container holding the electricity. Every day I learn something :)
Mr. Apol (author)  jj.inc4 years ago
Yes, this design does not contain any water, salt, etc.

jj.inc Mr. Apol4 years ago
Do you think I could use thin PVC for the same concept.
Mr. Apol (author)  jj.inc4 years ago
Possibly. What size PVC are you thinking of?

jj.inc Mr. Apol4 years ago
I am thinking about a mm thick piece, not pressure rated and a close to can sized as I can, if I can't find one that fits the can snugly do you have any ideas for a fix.
Mr. Apol (author)  jj.inc4 years ago
It has to be a snug fit, or it won't work very well. Perhaps you should consider a rolled capacitor made of plastic sheet and aluminum foil.

jj.inc Mr. Apol4 years ago
Also will like 1/4 inch thick pvc be to thick to work.
Mr. Apol (author)  jj.inc4 years ago
Leyden jars work best when the dielectric material is as thin as is practical. You can achieve capacitance with thicker material, but the total capacitance of the jar will be less than if you used thinner material. Also, you need some way to enclose the bottom of the jar, or it will arc to ground.

If powdered lemonade canisters are too hard for you to get, try 16 ounce hydrogen peroxide bottles. 12 ounce aluminum soda can fit them too. (See my other Instructable on Soda Can Leyden jars)

in the picture for step 5 are you using salt water capacitors because in the pictures there apears to be a liquid.
Mr. Apol (author)  makincoolstuff4 years ago
There's no liquid in these; what you see is a layer of wax poured into the top of the can to insulate it.

techno guy4 years ago
Is it better to link the capacitors in series, or parallel?
Mr. Apol (author)  techno guy4 years ago
If you mean in the Tesla circuit, I always wire them in series with the spark gap--one lead goes from the gap to the capacitors, the other lead off the caps goes to the coil primary.

See diagram here:


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