Capacitor Bank Series-Parallel Configuration

[MrScrOggs]

Hello everyone, I am building a capacitor bank and I am a bit confused about some concepts.

I know that this could kill me instantly, and understand the safety risks.
Each cap is 200v 2000uF (incase image is missing)
How many joules would this give me?
I understand series and I understand parallel but I can't grasp series-parallel YET.

[Mads Barnkob]

Putting two capacitors in series will double the combined voltage rating and half their capacitance

Putting two capacitors in parallel will double the combined capacitance and voltage rating stays the same.

You can use the MMC calculator to play around with different configurations in a very fast manner: https://kaizerpowerelectronics.dk/calculators/mmc-calculator/

Capacitor energy calculator: https://kaizerpowerelectronics.dk/calculators/capacitor-energy-calculator/

[MRMILSTAR]

Your schematic and picture shows 6 capacitors in parallel. This will yield an equivalent capacitance of 12,000 uf with a voltage rating of 200 volts. If you charged it to its maximum of 200 volts, the stored energy would be

E = 0.5*C*V*V = 0.5 * 12E-03 * 200 * 200 = 240 joules

Basically you just use a combination of series and parallel connections to give you the capacitance and voltage rating that you require. As far as energy is concerned it doesn't matter what the topology is, series, parallel, or series-parallel, the energy will be the same. Placing long strings in series brings the possible need for charge-distribution resistors. For that reason its best to minimize the use of series connections and to maximize the use of parallel connections.

What are you trying to accomplish with your capacitor bank?

[MrScrOggs]

Jeez only 240 Joules, that's actually disappointing.
I wanted to do can crushing and destroying small electronics.

[MRMILSTAR]

Jeez only 240 Joules, that's actually disappointing.
I wanted to do can crushing and destroying small electronics.

Here's a picture from my can crusher. You need at least 800 joules to get a decent theta pinch. You need a tightly wound work coil to get those results. I also use an Aerovox energy discharge capacitor.

[MrScrOggs]

Pretty dumb of me to buy such weak capacitors lol

[klugesmith]

Not so fast about saying weak. 

A bank of supercapacitors with same weight as your bank would store much more energy, but be even less useful for blowing things up, because supercapacitors are "slow". (They are fast compared to batteries).  Sure, they can put out enough current to melt a steel nail & leave energy in the capacitor. But your electrolytics could deliver vastly more current than the supercapacitors, for some milliseconds. Could easily explode a thin wire or, I bet, launch a disk. Hard to do that with supercaps.

My old can crusher might be exceptionally efficient, cause of special attention to minimize stray inductance.
12 oz cans cut in half with 1000 J, and detectably indented (if you know what to look for) with 30 J.

But it's got a high voltage oil-dielectric capacitor, and has discharge time constant of about 10 microseconds.
Electrolytics are inherently much slower than that, because of internal resistance.
Even with no internal resistance, for a given energy the C is too high and V too low.
To match that with a can-crushing work coil, you would need to wind it with less than 1 turn.

I think 1000 volts per turn is in the right ballpark for crushing cans to hourglass shape.
Seen reports of people doing it with 800 volt electrolytic capacitor banks, but I bet it takes plenty more joules of energy.

[davekni]

240J of electrolytics would be great for a coil-gun, launching a bolt across the room etc.  I use 20-40J and foam-wrapped nails for children's science activities.