another cap ?

[shooter]

I have boxes full of old computer grade caps, typical would be up to 50,000uF @50vdc
I’ve been toying with the idea of making a "catastrophic cap failure power supply".

Say 450vdc at 300mA for “testing” the computer caps.   My question, is the voltage differential the critical factor in failure testing or is current just as important?

[sluckey]

I’ve been toying with the idea of making a "catastrophic cap failure power supply".

Please tell me more! And why?

Plugging a 50V electrolytic into the wall socket will probably do a good job.   

[shooter]

Please tell me more! And why?

The more; ideally an "unplugged" DC power supply charging, think BIG CAP bank with 400-500vdc, big remote controlled switch, little(vdc) cap under test.

The why;  hmmmm, call it a proof of concept build, exploring the "merits" in accelerating gases/heat in various confined spaces 

my unknowns;
1 is voltage differential the biggest factor in failure, or does current play a big role.
2. Is failure "easier" if the test cap is wired backward.

[John]

1 is voltage differential the biggest factor in failure, or does current play a big role.

I've only popped one cap, and that was with almost zero current. But by Gawd, you exceed the voltage rating by about 50% cuz you weren't paying attention, and thar it blows.

[PRR]

When you get over 2X rated voltage, the current will get VERY high.

I suspect your 300mA supply will fail before you can blow-up a soup-can cap.

At best it will simmer slowly, not BURST.

Wall outlet should break-down 50V e-caps, but again the current may overload things (which could mean wall-fire). I'd advise wiring a 1,000W toaster or heater in series so the worst-case current isn't dangerous to the wall wiring.

You ARE aware that bursting caps, especially large caps, IS dangerous? And messy? I'd try it at the far end of a 50-foot extension cord down the driveway.

[HotBluePlates]

You ARE aware that bursting caps, especially large caps, IS dangerous? ...

I was thinking this earlier, then the phrase "natural selection" came to mind. 

[Willabe]

 

[silverfox]

proof of concept build, exploring the "merits" in accelerating gases/heat in various confined spaces

Use a number of  the caps in series in a voltage doubler circuit and fire the circuit with a Triac? through a pulse shaping network into a water filled glass ampoule with small gauge wire inside. Alternatively you could electrolyse the water in the ampoule and use a spark discharge instead of the wire. Those caps are probably too big to gasify at those voltages and at 120 watts would likely look more like a party popper.

I'm guessing you want to advance the science of mechanically digesting kidney stones in a water bath. The problem that arises though, if there is one, compared to chemically based kinetic systems this would be a large cumbersome solution. Compare your capacitor based system to say the Hitachi gas based Ram Set used to drive nails in the construction industry.

silverfox.

[shooter]

then the phrase "natural selection" came to mind

I have made it 59yrs so far doing "fertile mind" experimenting.
I am *safety conscience* my 35yr career mandates that, 5,000 to 144,000vdc WILL kill you quick if you're not on your game!

Thanks PRR, I figured it would take current, lots, I just wasn't sure since cap rating I've looked at never really
*emphasize* that like other components.

this would be a large cumbersome solution

I think you're right silverfox,

If *it* goes anywhere i'll post my findings

[PRR]

> I figured it would take current, lots, I just wasn't sure since cap rating I've looked at never really *emphasize* that like other components.

Well, they do tell you a limit voltage. Anything past that is *your* problem.

Expecting (hoping-for) overload details like that is like overload info on a water-heater. They say it is good for 50psi, and they leave a margin of safety. But they are not likely to answer "if I pump/heat it to 500psi, how high will it fly?" That information is out there; MythBusters blew/flew a few water heaters, and I am sure it is a popular pastime on YouTube. Likewise you can probably find cap-explosion videos online. But you aint supposed to do that, and the makers are not eager to tell you what could go wrong.

It's a can of electrolyte. Steady current flow is blocked by a micro-thin layer of oxide. If you break that down, it becomes a can of soup with large electrodes. I would expect a large can of highly salted soup to flow a LOT of current; I would think that for low ESR the cap-electrolyte is at least as conductive as salty soup.

[shooter]

MythBusters blew/flew a few water heaters

That was fun to watch

I would expect a large can of highly salted soup to flow a LOT of current

Thanks again, I have replaced - cleaned up splattered caps, I just didn't take the time to *understand* the actual process, since I was paid well to fix it, then move on to the next *fire* But this site, gets me to use my gray n white matter at a deeper level then fix it n forget it