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can electrolytic capacitors catastrophically fail or explode if they are shorted out?

My father (an electrical engineer) told me that if a capacitor is charged and than shorted out than it can fail, possibly with explosive results. However I have seen way to many Youtube videos of capacitor banks being shorted and nothing but a big spark happening. Who is right? Can anybody help me?

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I doubt that a properly functioning electrolytic would explode if shorted...If reversed, overheated, physically decayed or overloaded then yes they can explode (or at least leak goo all over). When my electronics instructor tried to demonstrate this for us he tripped the breakers for the entire electronics lab (it may have had something to do with the GFI on the building though). High voltage caps can be safely discharged through resistors, just be sure to do the math on the power you will be putting through the resistor and adjust wattage to suit. If you don't mind sparks just touch the leads together. As a sidenote high voltage caps should always be stored with the leads shorted (with wire or a resistor), ambient air in certain environments can charge caps to their full rated voltage. Always assume caps which are not shorted are charged and handle accordingly.
Kb1ltg.11 months ago

Those who have commented that they "Didn't think they would explode" are dead wrong! I just replaced a 300uf Starting capacitor on a large air compressor whose "Start" normally closed switch failed to open upon motor coming up to rpm. It exploded violently after about 5 seconds of motor full speed operation, sending hard plastic, hot electrolyte and metal fragments all over. I was hit in the face with a piece of plastic and it drew blood. You bet, they CAN explode.....The "Best" answer below is based on supposition, mine on real life experience....

junits15 (author)  Kb1ltg.7 months ago

Caps don't explode when shorted, they explode if wired in reverse, you may have wired that cap in reverse, or something else may have been wrong with it. Caps can deliver many hundreds of amps instantaneously.

I’ve never had one explode from being shorted but they can explode from being over charged, over heated, and with the polarity reversed and I have had that happen before. Super capacitors will be damaged if they are shorted but i’ve never heard of them exploding from it. Some electrolytic caps have a vent on the top its an x shaped indent and those will blow out if it fails, but if it doesn’t have one the whole can will shoot off I saw one go 50 feet once. Don’t breathe the smoke if one does blow I heard it was toxic.
Flash6358 years ago
If you plug them in to 240v 10 amps they blow up real good!
rich_moe8 years ago
This one is from personal expirience... I was working on a RADAR system for the miltary. On the test stand, the receiver-transmitter was running, warming up to operating temperature. The timer circuit was inoprerative, so the repair manual said to cycle the system off, then on again. Turned the system off, waited the 30 seconds, turned the system back on, and *BOOM*! An electrolytic filter capacitor in the low-voltage power supply exploded, taking off the end cover of the R-T. The end cover was a compression flange-ring type, and it went about 20 feet across the room. Short answer...Yes. These were metal-film electrolytic capacitors. And, it was one of the small ones, in the range of 120 uF.
gmoon8 years ago
They can certainly explode if their polarity is connected incorrectly (i.e., opposite.) I've done it ;-)

And I believe that HV caps can also fail catastrophically during discharge.

For instance, if one capacitor in a bank of caps has an internal flaw, then the rest of the caps in the bank can all discharge into the fault. All that energy flowing into a defective (shorted) cap will very likely cause explosive failure, by vaporizing the liquid dielectric in an electrolytic capacitor.
Plasmana gmoon8 years ago
Haha, that is cool, I have one time over loaded (voltage) an small capacitor and it explode with an resulting of a very loud bang, it is louder than a M-80 firecracker and it is so loud that the bang echoed around my neighborhood... :-)
goodgnus8 years ago
I have personally witnessed capacitors, large ones, several inches in diameter and many inches in length (used in automotive stereo applications to provide extra power for subwoofer amplifiers) explode, and I mean EXPLODE.
but they have a low voltage rating (ie- 12-14V) so easily made to explode.
UziMonkey8 years ago
My teacher once demonstrated shorting out a bank of really huge electrolytic capacitors. It arced several inches through the air and made a huge pop, but no explosion. However, if you were to apply too high a voltage or put them in backwards, you can expect an explosion.
Plasmana8 years ago
Your father might be right about old capacitors, but on newer capacitors, they don't seem to explode. However, the newer capacitor can lose capacity and useful life if shorted harshly.
dark sponge8 years ago
I don't think they explode when shorted, but I do know form firsthand experience that they can explode if you go over their voltage limit.