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Chemical question electrolytic capacitor


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I think the question is more about the lifetime of the device, not how long it holds a charge.

Googled [ shelf life of electrolytic capacitor ] ... but was confused by the results as they seem to imply pretty much any device I have (that has such caps) that's older than three years should begin to fail! Must be missing something.

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1 minute ago, pzkpfw said:

I think the question is more about the lifetime of the device, not how long it holds a charge.

Googled [ shelf life of electrolytic capacitor ] ... but was confused by the results as they seem to imply pretty much any device I have (that has such caps) that's older than three years should begin to fail! Must be missing something.

yes

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My hobby is computer hardware, and I have built/modified many.
About 15 years ago, a lot of my motherboards showed signs of failing electrolytic capacitors, with the typical bulging end.
I desoldered and replaced quite a few on many motherboards.
There were some reports in computer magazines, at the time, that failiures were caused by badly formulated electrolite as a result of bungled industrial espionage. See here ...

Capacitor plague - Wikipedia

I had never seen that problem before, and it has virtually disappeared again, as most electrolytic caps are used for decoupling, and although their specs may vary quite a bit over time, they are still adequate for their intended purpose.
( if the specs are critical, use a better quality, and much more expensive, sealed type )

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  • 3 weeks later...

electrolytic capacitor of electronic devices is a component that involves chemistry, the electrolytic capacitor mounted on an electronic circuit can remain unused and without power for how long without its disuse affecting the useful life of the electrolytic capacitor? i have old electronics devices of 1990

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electrolytic capacitor of electronic devices is a component that involves chemistry, the electrolytic capacitor mounted on an electronic circuit can remain unused and without power for how long without its disuse affecting the useful life of the electrolytic capacitor? i have old electronics devices of 1990

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  • 2 weeks later...

electrolytic capacitor of electronic devices is a component that involves chemistry, the electrolytic capacitor mounted on an electronic circuit can remain unused and without power for how long without its disuse affecting the useful life of the electrolytic capacitor? i have old electronics devices of 1990

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Posted (edited)
15 minutes ago, gamer87 said:

electrolytic capacitor of electronic devices is a component that involves chemistry, the electrolytic capacitor mounted on an electronic circuit can remain unused and without power for how long without its disuse affecting the useful life of the electrolytic capacitor? i have old electronics devices of 1990

This is not so much a question about chemistry as about the shelf life of specific manufactured items. I found this link, which may point you in the direction of an answer: https://electronics.stackexchange.com/questions/8794/do-electrolytic-capacitors-have-a-limited-shelf-life

From this it rather looks as though trying to put into service a 30yr old component may not be a good idea.

Edited by exchemist
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What I don't understand is why after extensive explanation and help (from some very knowledgeable people) asking this very question at PhysicsForums you seem to be looking for some different answers here.

It should be noted that electrolytic capacitors are not the only components with a definite life.
They are just the most notorious offenders.
Personally I have mostly been lucky with them.
The last capacitor that died on me was last year in a high end CD deck.
It was a resin encapsulated super mains filter capacitor.

The problem is that for some unlucky  folks their mains supply is very 'dirty' (has many spikes and transients).

Capacitors are meant to absorb the energy of these, which they do,

But each time this happens a small amount of damage occurs to the capacitor until eventually it burns out and needs to be replaced.

As components become smaller and smaller this effect has become more marked as the energy density is necessarily greater in a small component.

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An electrolytic capacitor is two thin aluminum sheets with an 'oil' impregnated paper separator between them..
This is rolled-up into a tube, encased in an aluminum or plastic housing, and capped at either end wth rubber, through which, the connecting leads are passed.
This is by no means a sealed assembly. Over time, the 'oil' impregnating the paper, tends to dry out, even without use. 
With use , the process of drying out is posibly accelerated due to increased temperatures.

This 'oil' is not simply oil, but an organic chemical compound, selected for various properties; most important are dielectric properties, temperature resistance and stability over time, AND resistance to drying out.

As no electrolytic capacitor manufacturer provides 'lifetimes' for their products, it is basically a crap-shoot as to whether thyll still have the same capacitance after many years. Their 'lifetime' will certainly exceed the manufacturer's warranty of the product they are in.
If, on the other hand, you are designing equipment, and don;t wish to run into such problems, use a more expensive sealed type of capacitor, but as Studiot explained, those have failure modes also.

Please don't ask the same question a 5th time.

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