What happens when you put an electrolytic capacitor the wrong way?

[Greyersting]

I would rather someone tell me instead of trying it out myself.

[c4757p]

The oxide insulator on one of the foils erodes, causing the capacitor to become conductive. It becomes a short circuit, conducts a metric assload of current, and gets hot. Then the electrolyte fluid boils, building pressure, and it pops.

Try it yourself with one that has a safety vent. Why? Because big bangs are fun. But don't do it with a cheapo non-vented one or you could put your eye out....

Dude... get your email address out of your signature, that'll be sniffed up faster than you can say "spam"...

[w2aew]

I would rather someone tell me instead of trying it out myself.

You'll let the magic smoke out. Sometimes even with a bang.

[TonyPh]

I connected a small electrolytic cap backwards once. It was unvented. When it blew it scared the crap out of me.  I'm always cautious now when wiring something up to the point where I close my eyes and grimace the first time I apply power to a circuit, just in case. 

[andtfoot]

I'm suprised no one has posted this yet...



(among all of the other videos on youtube of capacitors exploding)

[Crazy Ape]

I saw a 22uf electro get embedded in a someones neck once.

[electrosam]

If you put an electrolytic capacitor in the wrong way momentarily it will sustain. As a matter of fact when you are using it to bypass AC it does receive reverse polarity for smaller amounts of time. However if you reverse the polarity for longer duration with significant voltage across it, it will explode !

[SeanB]

If you use a wet slug tantalum capacitor it makes a far impression of a bullet, I broke a window once with one, it went through and left a hole.

[olsenn]

Question: What happens when you put an electrolytic capacitor the wrong way?
Answer: BOOM!

[odv000]

what will happen?
BOOM!
and also horrible smell.

If you put an electrolytic capacitor in the wrong way momentarily it will sustain. As a matter of fact when you are using it to bypass AC it does receive reverse polarity for smaller amounts of time. However if you reverse the polarity for longer duration with significant voltage across it, it will explode !

it's not always the case. usually if you look carefully on circuit (or just measure voltage ) you will find out what there is AC on top of DC applied to cap so it will not get charged backward.

[c4757p]

The classic voltage doubler circuit that is (or used to be) commonly seen can reverse bias the capacitor at startup. However, unless I have my capacitor chemistry wrong, biasing it correctly can actually repair the small damage caused by a very short reverse bias condition.

[david77]

I once saw a mate testing a power supply he'd just built up. Then there was an almighty BANG, smoke, fluff and my friend screaming and holding his bloody face.

After he'd calmed down we assessed what had happened. He put the big smoothing cap in the wrong way across a DC rail of about 40V and several amps. I can't remember but I'd say it was a 2200uF/50V cap, pretty substantial piece of kit. We were teenagers then and the thing probably came out of some old piece of junk - that makes it very likely it was unvented - this happened nearly 20 years ago so that puts the piece of junk we ripped it out of in the middle of the 70ies. 2200uf caps used to be a lot bigger than today, kids!

The aluminium cap had hit him on the upper lip right under his nose from a distance of about 30-40cm. His lip was swollen and he had a nose bleed. He said it was like somebody punched him on the nose.
Today we can laugh about it. Could very well have hit an eye...

If you want to try it use something small, like 1µf or so...and think about what you're doing!
I just let a cap pop when I saw this thread, it's still fun  .

[ablacon64]

Funny video! kkkkkkk... Try it with a little bigger capacitor.      

[Nerull]

If they're properly vented, bigger caps are actually less spectacular.

Unvented ones, though...

[JoeyP]

I saw a 2" hole in a drop ceiling once because someone exceeded rated voltage for a while on a good sized can. So, it's not just reverse bias that will do it.

I exploded one when I was a kid, and aside from the mess, the smell was the worst part. Absolutely disgusting smell that lingers for days.

[Phaedrus]

Once had a 1200W SMPS left on a load tester idle, with just a 1A load @3.3V. It sat there maybe an hour, then out of nowhere--BOOM!!! The PFC capacitors, a pair of 560uF 420V numbers, both went nuclear! Unbelievable, that would happen with only about 20W of AC input (not very efficient at that low load). Still not sure what caused it; it was the first time this had ever happened, and the product was due to EOL, so the CEO told us not to waste time diagnosing. I disagreed, but followed orders.

Anyway, the whole lab stank like toad cheese for two whole days, even with the window open and a fan blowing. Disgusting.

[HWM]

if Electrolytic capacitor was used in decoupling mounted in reverse polarity, will it explode immediately?

[extide]

This is what happens

[vk6zgo]

 Often, it will  go bang, but sometimes, nothing obvious will happen.

I was refurbishing a Sony BVM 2000 Monitor one time, & found a number of electrolytics on one board were installed "the right way round" according to the "silk screened" markings on the component side of the PCB, but reversed, according to the markings on the other side, as well as the schematic.

This device had been in service, meeting all specifications, for around 10 years!
Needless to say, I replaced them the right way around as per the schematic.

On another occasion, "in another place", I replaced all the electros (big ones) in a rack mounted PSU in an AM Broadcast Tx site "speech input room".
Unfortunately, it was a -24v supply, & I mindlessly fitted the caps as for a positive supply.

At turn on, there was a loud "Bang!" & the air was full of capacitor guts----it looked like it was snowing!

On another occasion, a trainee gave me his project (A Dick Smith Electronics kit), to check the wiring.
From a cursory inspection, all was well, right components, excellent soldering, & so on.
Having got my approval, he switched  it on.

There was a sound like a 0.22 rifle shot, & the case of an electrolytic blew its end open (It was a small  cap-- the big ones sounded like a shotgun)

Dear old DSE had marked the board wrongly, so I wouldn't have been able to pick it without a much closer look.
Even so, I think the trainee lost a bit of faith in my supervisory capacities!

[Nerull]

http://youtu.be/HEc5Juq7TaQ?t=593

The Amiga CD32 came with capacitors installed backwards from the factory.

[GreyWoolfe]

This:

[John B]

The classic voltage doubler circuit that is (or used to be) commonly seen can reverse bias the capacitor at startup. However, unless I have my capacitor chemistry wrong, biasing it correctly can actually repair the small damage caused by a very short reverse bias condition.

Not only startup but excessive current draw on the voltage doubler will also reverse bias the caps.

[T3sl4co1l]

Also, as long as we're pulling out memes:



Tim

[bd139]

Lame. Some russian capacitors:

[MagicSmoker]

Well, that escalated quickly...


...sorry, couldn't resist the way-too-apropos Ron Burgundy quote.