Liftime of wet capacitors

[kkrafs]

Im doing a inventory of my components and got stuck
on the issue for the the lifetime of wet electrolyts!
I have pile of NOS jamicon, Elna ,Rubycon etc , all
about 12-14years old, newer used in a cirquit all
are standard series, how long can their shelf life
be in 25 deg C?

Is there any (in cirquit normal op) liftime parameter
on wet electrolytics actually ? I know wet lyts will
eventually dry out.

Most manufacturers shelf parameter states 85deg C and above!
I have stored them for all these years at 25degC.

Should i trow them or not?

Kkrafs

 

[NewYorkDave]

I've used 12 year-old 'lytics with no problems at all. Most of my personal component stock was purchased around 1993, when I had enough "disposable income" to buy my parts in large lots.

It's always a good idea to bring the voltage up slowly--and limit the current--when using them for the first time. Some people go nuts over "capacitor forming", ramping them up over the course of many hours, but I think that's probably overkill unless the caps are very old or have been stored in poor conditions.

 

[kkrafs]

And what if the capacitors have been stored in dry but
quite cold temperatures , at peeak (some times) -30 degC?
I have a box of about 50pieces of 25000uF quality capps ,
i newer have come around the corner to use them,so they
have been in the garage for about 10 years!

Kkrafs

 

[clintrubber]

[quote author="kkrafs"]And what if the capacitors have been stored in dry but
quite cold temperatures , at peeak (some times) -30 degC?
I have a box of about 50pieces of 25000uF quality capps ,
i newer have come around the corner to use them,so they
have been in the garage for about 10 years!

Kkrafs[/quote]

A (Philips) databook on alu caps says lifetime doubles for each drop in temp by 10'C. Don't know if that could be considered an universal statement, but it sounds familiar w.r.t. chemical processes.

When put on the shelf, being charged i.s.o. 0V is also healthy w.r.t. lifetime, but somewhat impractical.

Like NYDave said, at least 'initialize' them before use, and likely a simple action will be good enough. If it's a cap to be used on a critical spot (like the big cap in series with a mic-pre-gain-pot) you can go of course a bit further than when it's the big cap for say a DC-heater supply.

Regards,

Peter

 

[pmroz]

Most manufacturers shelf parameter states 85deg C and above!

That can't be right, can it?
Pretty hot.
If it says 85deg celsius I think that's the rated maximum temp it will tolerate before it pops.

 

[clintrubber]

[quote author="pmroz"]

Most manufacturers shelf parameter states 85deg C and above!

That can't be right, can it?
Pretty hot.
If it says 85deg celsius I think that's the rated maximum temp it will tolerate before it pops.[/quote]
What I saw today w.r.t. shelf life definitely started at -40'C, not 85'C. That 85'C will not unlikely be the max value of the shelf-temp.

 

[Guest]

Is the stuff inside them dangerous?
I had a pulled the legs of a FC cap by mistake and accidentally put it into my tool box.
I put my hand in to label it and wondered what the fluid was.. and then I wiped it all over my pants (underwear).. (stop sniggering at the back.. it was to clean my hands)
And I then I realised WTF have I just done

And second question - I have some 1968 Marconi Electrolytics never been used - tight tolerance used for Radar stuff - bin them or keep em?

 

[clintrubber]

[quote author="uk03878"]Is the stuff inside them dangerous?
[/quote]

Yes, very much so as I understood. Maybe not as bad (causing cancer) as before, but take care (repeat ten times).

 

[kkrafs]

OK, toughtful ideas you proposed folks
but how do i test the 15000uF cap?
Ripple and leakage can easily be tested but testing
Farad values turns out to be an awful long time
constant to test!!

Any ideas on how shorten it?

Kkrafs

 

[clintrubber]

[quote author="kkrafs"]OK, toughtful ideas you proposed folks
but how do i test the 15000uF cap?
Ripple and leakage can easily be tested but testing
Farad values turns out to be an awful long time
constant to test!!

Any ideas on how shorten it?

Kkrafs[/quote]
What do you want to know ? The cap-value ? You could determine that by feeding it a fixed & known current (that's well above the leakage current) and measure the applied time & resulting voltage increase.
C = I*dt/dV

Bye,

Peter