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Old 01-28-2019, 07:44 PM   #1
eccerr0r
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Default Overvolting/reversing a polymer cap

Just curious, have anyone videoed over volt or reverse connected polymer capacitors and posted how they fail?

IIRC most of the videos I've seen are of cheap wet aluminum capacitors which are fairly spectacular, but what about polymer - do they mainly fail the same way? Or not?

The wet aluminum capacitors will expand due to vapor generation of the liquid electrolyte and could blast off. Polymer capacitors have two transition phases from solid to liquid and then liquid to gas... so do they do the same thing or simply immolate on board?
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Old 01-28-2019, 11:05 PM   #2
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Default Re: Overvolting/reversing a polymer cap

there is a vid on jtube,
a bussbar with a line of poly's on it - they short out - presumably, because on most the leads melted!!
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Old 01-28-2019, 11:51 PM   #3
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Default Re: Overvolting/reversing a polymer cap

So they fail like tantalum caps in which they simply short out? hmm... okay...

Well, after they short then they differ I suppose, tantalum capacitors tend to immolate, but not polys?

Last edited by eccerr0r; 01-28-2019 at 11:58 PM..
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Old 01-29-2019, 07:05 AM   #4
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Default Re: Overvolting/reversing a polymer cap

the poly's may have flared if they had been flush on a board - who knows.
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Old 01-30-2019, 08:40 AM   #5
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Default Re: Overvolting/reversing a polymer cap

heatup and smoke, charred the bottom
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Old 01-31-2019, 12:56 PM   #6
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Default Re: Overvolting/reversing a polymer cap

Reason why I'm asking:

Destructive testing to prove a cap is a polymer cap versus an aluminum wet electrolytic
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Old 01-31-2019, 02:33 PM   #7
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Default Re: Overvolting/reversing a polymer cap

or just cut into it.
esr test will be conclusive anyway - the worst poly still blows away the best wet caps.
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Old 01-31-2019, 03:46 PM   #8
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Default Re: Overvolting/reversing a polymer cap

If one doesn't have an ESR meter that has enough resolution, that's not an option...
Was wondering about cutting into it and sensing any sort of moisture, but that's no fun
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Old 01-31-2019, 05:55 PM   #9
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Default Re: Overvolting/reversing a polymer cap

Well this is all the inspiration I need, what values did you have in mind and you you be prepared to send said samples for 'testing' I can currently manage 30 volts at 20 amps or 60 volts at 15 amps. Let me know if you want to do this I can video the results
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Old 01-31-2019, 10:30 PM   #10
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Default Re: Overvolting/reversing a polymer cap

Great, you can buy the stj clickbait capacitors to test
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Old 02-01-2019, 03:31 AM   #11
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Default Re: Overvolting/reversing a polymer cap

I am not buying perfectly good capacitors to slaughter, but if some one wants to send me some for destructive testing I will be more than happy to oblige and put the results up on my youtube channel. Who knows if there is enough interest I might rebuild my old high voltage capacitive discharge rig which was good well up-to 20,000v.
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Old 02-01-2019, 04:11 AM   #12
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Default Re: Overvolting/reversing a polymer cap

Who said they were perfectly good capacitors, that's what we're trying to find out if they are or not

So if you had to go buy some brand new Rulycons would they be considered perfectly good capacitors
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Old 02-01-2019, 07:53 AM   #13
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Default Re: Overvolting/reversing a polymer cap

lol
that psu output sounds familiar.
is it military surplus?? wayne kerr???
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Old 02-01-2019, 03:17 PM   #14
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Default Re: Overvolting/reversing a polymer cap

It's been 10 years or so, but I think that when I tortured some polymer caps - 8X or 10X their ripple current rating - they just deteriorated slowly. I probably declared victory when they reached 2X their initial impedance.
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Old 02-01-2019, 04:27 PM   #15
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Default Re: Overvolting/reversing a polymer cap

Heh, the intent for killing these "clickbait" polymer caps was to compare how they explode compared to wet aluminum capacitors to determine their internal design. Yeah it's not accurate at all but there's at least one person here who's interested in watching them explode if at all...

Question too for using more current than they're designed to handle is how long did it take at 9x current rating to reach 2x impedance... 1/10 of their rated lifetime? 1/100th?
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Old 02-02-2019, 08:41 PM   #16
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Default Re: Overvolting/reversing a polymer cap

Well I have put the offer out there, Uk mailing address to be supplied via private message to interested party's. If you want to send me a selection of test subjects I will oblige in over volting and reverse volting them for your viewing pleasure. Bench test voltages available in case you missed are 30 volts @ 20 amp and 60 volts & 15 amp, results to be published on my youtube channel. The 20,000 rig was probably mostly military surplus parts I still have some of the parts but would have to hunt around to resurrect it, oh fond memories.

Last edited by llonen; 02-02-2019 at 08:44 PM..
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Old 02-03-2019, 04:31 PM   #17
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Default Re: Overvolting/reversing a polymer cap

Darn, already done ... https://www.youtube.com/watch?v=BNaVokFOxjo

So all I need to do is abuse it and it better not pop, just short out...
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Old 02-03-2019, 05:55 PM   #18
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Default Re: Overvolting/reversing a polymer cap

Needs more voltage, or lower voltage polys, I have had another look at the power supplies I have here, I can get up-to 60 volts with 32 amps available, on the high voltage side I can relatively easily get up-to 10kv @ 1uf. That will be around 50 joules assuming I can get it to full charge, it looks though I no longer have the 20kv caps though. I wont be checking this thread now so if there is any interest just pm me.
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Old 02-03-2019, 07:50 PM   #19
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Default Re: Overvolting/reversing a polymer cap

And if not, "I ain't having it, where's my hammer?"
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Old 02-04-2019, 02:23 PM   #20
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Default Re: Overvolting/reversing a polymer cap

Quote:
Originally Posted by eccerr0r View Post
...
Question too for using more current than they're designed to handle is how long did it take at 9x current rating to reach 2x impedance... 1/10 of their rated lifetime? 1/100th?
Pretty sure it was hundreds of hours if not over a thousand. Not bad for 2000 hour (at max ripple and temp) parts. It was ~10 years and two jobs ago, so hazy memories.
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