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Capacitor's voltage rating

CaptainTuna's picture

Hi guys.

Do you know what the voltage rating on capacitors is? My idea is that the voltage rating is just the maximum voltage it can take before the blue smoke comes out, but i'm not sure.

thank you :) 

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anachrocomputer's picture

Yes, the voltage rating on a capacitor is the manufacturer's estimate of the maximum voltage that it's safe to charge the capacitor up to.  Now, you might want some margin of safety, so you might not use a 12V rated capacitor at the full 12V all the time.  Better for reliability to choose, say, a 25V capacitor in a 12V application.

And yes, capacitors can explode if charged up beyond their rated voltage.  It's not a "firey" explosion, more of a build-up of gas pressure that eventually bursts the seals.  Doesn't smell very good, either.

jklug80's picture
A few years ago motherboards had capacitors leaking and exploding in PCs. My company bought thousands of PCs from Dell for the companies tech refresh. We bought them at the height of the time the faulty capacitors were used. We had to swap out over 6,000 motherboards. They usually just leak and vent the heat. Not really a huge explosion unless you are using WAY too much voltage.
sprongll's picture

i think thats the theory.

I'm pretty sure i read somwhere to use caps rated at twice the nominal voltage in your circuit, so i tend to stick to that idea, and so far have had no problems... yet

Nicola's picture

yes, that's true becouse, afaik, not only the blue smoke came out but they can easily explode.

Once at school it happened that one exploded.. the metal case remained embedded on the ceiling :)

CaptainTuna's picture
wait wait, they exploded because they did not exceed the battery's voltage or twice as the battery voltage?
Nicola's picture
They can explode if you charge them over their specified rating. That's why you want at least double of your battery voltage, to be on the safe side.
Krumlink's picture
Pretty much yes.