Leyden Jar Battery 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.

Step 1: The materials

Modern experimenters are lucky. We have access to materials early electricians could not imagine. Our households are populated with all sorts of interesting plastics, metals, and artifacts useful for high voltage experiments. In an earlier Instructable I described my Soda Can Leyden Jar. The basic unit of the Tesla Coil Leyden Jar array is very similar to the previous design.

To start with, you will need:

-a number of powdered drink mix canisters (Crystal Light or its generic equivalent)
-an equal number of aluminum soda cans (brand does not matter)
-aluminum ductwork tape (do not use silver fabric duct tape--it will not work!)
-plain, uncolored and unscented wax or paraffin; a pound will seal 6 of these jars
-16 gauge (or better) electrical wire; about 6 inches per jar
-large rubber bands
-a polyethylene storage box large enough to hold the array.

Everything needs to be clean, dry, and label-free. The exception are the soda cans. Soft drink logos and other graphics are usually applied as sleeves to the sides of the can. The top and bottom of the cans are bare metal. They require only a quick wipe with a solvent like acetone or xylene to get them clean and ready for electrical connection.

The drink mix canisters are made of polypropylene (PP). They measure 6.5 inches high ( about 16.5 cm) and 2.625 inches in diameter ( 65mm). They are straight side cylinders. The plastic is fairly thin and quite strong.

There are a number of brands of aluminum tape. For ductility and strength I like Henkel's Duck Brand HVAC Metal Repair tape. I prefer the two inch wide tape. You can find aluminum tape in 3 inch widths, but 2 inch gives you greater flexibility in how much surface you cover.

The 16 gauge wire is rated for 600 volts. I salvage all I need from old microwave ovens, CRT monitors, and old TVs. All the lengths you will use will be pretty short, so all those odd pieces you salvage will be useful. You can buy wire, of course. Get at least 16 gauge, at least 600 volts.

Wax is used to insulate the top of the soda can after the jar is assembled. Be sure to use plain unscented wax or paraffin. Wax is a good insulator, but dyes and scented oils may not mix well with high voltage electricity.

Rubber bands help bind the cluster of jars together. It is important the outside foil coatings of the jars make good contact with each other.

Since you will be running anywhere from 6,000 volts and up from a transformer through the Leyden jars, you'd better have a good insulated container for them. Storage boxes made of HDPE (high density polyethylene plastic) work well.

Comments

[sara rarara]

lets say 40,000 v is enough but its difficult to find b/c new TV circuits doesn't fulfill requirement

[sara rarara]

its now love for Tesla coil !!

[sara rarara]

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 rarara]

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]

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.

Paul

[sara rarara]

http://www.instructables.com/id/Step-By-Step-Plans-to-Building-a-250000-Volt-Tesl/?ALLSTEPS

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]

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?

Paul

[sara rarara]

can we use this for 10,000 capacitance and how?

[Mr. Apol]

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.

Paul

[rayfalcon]

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?
[e-mail]
Charles

[Mr. Apol]

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.

Paul

[thanatos370]

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.

[mark2502]

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
Thanks,

[Mr. Apol]

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.

PBT

[Adrenal1ne]

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]

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.

Paul

[Adrenal1ne]

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

[Mr. Apol]

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.

PBT

[Kalace]

Great thinking and work, for using leyden jars for tesla coil caps, i will have to try these out some time.

[Mr. Apol]

Let us know if you build some of these.

Paul

[jj.inc]

So it is just empty air space, not salt water or anything.

[makincoolstuff]

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.

[jj.inc]

Thanks, I finally figured out that it is the walls of the container holding the electricity. Every day I learn something :)

[Mr. Apol]

Yes, this design does not contain any water, salt, etc.

Paul

[jj.inc]

Do you think I could use thin PVC for the same concept.

[Mr. Apol]

Possibly. What size PVC are you thinking of?

Paul

[jj.inc]

Also will like 1/4 inch thick pvc be to thick to work.

[Mr. Apol]

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)

Paul

[jj.inc]

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]

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.

Paul

[makincoolstuff]

in the picture for step 5 are you using salt water capacitors because in the pictures there apears to be a liquid.

[Mr. Apol]

There's no liquid in these; what you see is a layer of wax poured into the top of the can to insulate it.

Paul

[techno guy]

Is it better to link the capacitors in series, or parallel?

[Mr. Apol]

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:

http://home.gallatinriver.net/mhammer/coil.htm

Paul

[greymatter21]

where could i find a tesla coil?

[Mr. Apol]

Pre-made coils are usually both expensive and not very impressive in performance. (See http://sciencefirst.com/product_info.php?products_id=632&osCsid=c43768f1e072b0f51253f1ccf42de184 for example). Sometimes you can find handmade ones on eBay. 

Why not build one yourself? What purpose do you have in mind?

Paul

[greymatter21]

i dont even know what tesla coils are used for....

[Mr. Apol]

Mostly they're demonstration devices--you can show all sorts of scientific phenomena with a Tesla coil. And they make cool, enormous sparks. Mostly they are an end to themselves.

PBT

[greymatter21]

are they safe to touch tha sparks?

[Mr. Apol]

Short answer, No. There are people who do this, but if you don't know exactly what you're doing, you can easily electrocute yourself. Why risk it for a stunt?

PBT