Electrolytic Capacitors

[Roy D. Mercer]

Assuming they are stored at room temperature, will electrolytic capacitors have an increased shelf life if stored in airtight containers?

[Gyro]

I very much doubt it, diffusion through the seals is very low at room temperature anyway.  The main 'shelf-life' mechanism is the oxide layer on the aluminium foil degrading without bias voltage. Low storage temperature probably makes a difference, but then you might get corrosion problems from humidity etc.

I'm not sure, but charging Electrolytics to normal operating voltage occasionally (and then discharging them) might 'reset' the shelf life clock.

In reality, storage isn't normally that much of a problem anyway.

[Zero999]

I've never had a problem with storing electrolytic capacitors. I've used 25 year old, unused parts before without any problems.

[rx8pilot]

There are a couple of surplus electronics shops close to me and I have used what appear to be VERY old caps (unused) that seem to be just fine. Old as in decades for some of them.

[dave_k]

I've never had a problem with storing electrolytic capacitors. I've used 25 year old, unused parts before without any problems.

Keep in mind, you're also missing out on 25 years of advancement in capacitor design and construction ..

[David Hess]

If you store enough capacitors in an air tight container for months to years, then upon opening the container, you can sometimes smell the electrolyte leakage.  But just storing a decades old but working can style capacitor in the same container for a week or less produces a stronger smell so I doubt storing them that way will improve storage life.  It is not that they leak a lot but that your sense of smell is pretty sensitive.

As far as beneficial storage conditions, I would go with low temperature.

I disagree with Gyro about the wearout mechanisms.  Newer capacitors do not significantly degrade without bias and the corrosion problem is to do ingress of water and/or oxygen.  If you open old can capacitors which have failed completely open, you will find that the strip of aluminum between the external lead and capacitor element has corroded to aluminum oxide.

[rdl]

I guess I need to investigate how to check if an old electrolytic capacitor is still good. I have a bunch of Panasonic TSW that I'm certain were bought before 1990.

[Cubdriver]

I guess I need to investigate how to check if an old electrolytic capacitor is still good. I have a bunch of Panasonic TSW that I'm certain were bought before 1990.

I would bet that unless they were stored in awful conditions that they are likely to be just fine.  Run some of them up to their rated working voltage with a power supply while watching their leakage current, and/or put them on an LCR meter and check their value and ESR if you want to be sure.  Panasonic is a pretty well regarded manufacturer as far as component quality goes.

-Pat

[calexanian]

Generally capacitors made from the 80's on are pretty well sealed. If they have never been formed or installed they should form normally and be functional. Generally the life ratings are for time in use. Forming has a lot to do with how they last. rated voltage vs the voltage they are formed and used at, etc. That is less important these days as most caps are generally pre formed. always form old questionable source caps out of circuit first and make sure they are not massively leaking current or have dried up and no longer have any capacitance before use.

[andy2000]

I've seen a lot of bad capacitors from the late 80's to early 90's.  Panasonic VCR power supplies used to be full of leaking caps even back when they were less than 10 years old.  SMD caps from that time period were also notorious for leaking.  Your caps may be fine, but I would check very carefully for signs of leakage around the leads. 

[calexanian]

I've seen a lot of bad capacitors from the late 80's to early 90's.  Panasonic VCR power supplies used to be full of leaking caps even back when they were less than 10 years old.  SMD caps from that time period were also notorious for leaking.  Your caps may be fine, but I would check very carefully for signs of leakage around the leads.

Oh yeah. I forgot about the SMD cap plague and the cheap Asian cap plague. We always have bought name brand, mostly Illinois Capacitors during that time at our company so we were spared the problems.

[innkeeper]

I recently reformed a bunch of 2200uf 50v nichicon caps made in 1981  so over 36 years old.
they tested fine, and are in service after the necessary reforming.
I am using them in some power supplies. I have a bag of 100 of these, and yet to have one bad one.

i've had cheap no-name brand caps go bad a heck of a lot sooner then 36 years, and i'm sure most of us ahve seen this first hand.

so i believe it has more to do with the quality of the cap, and how well its seal holds up. if it has bad seals or seals that srink over time, its gonna leak, no amount of sealing it in a containers going to fix that.

[IanMacdonald]

I think temperature and ripple current both have a lot to do with determining life. In valve equipment heat is the killer, in SMPS it's ripple current. Which is why the SMPS input caps rarely fail; the ripple is much greater on the LV side.  In storage they certainly keep for a few decades. Exactly how long, hard to say.

[Roy D. Mercer]

Thank you very much to everyone that applied. How do I ensure an email notification when someone responds to my post?

[Neomys Sapiens]

I can personally attest no degradation outside of specs for the standing (radial) brown Roederstein types as well as large Siemens SIKOREL after 25 years since manufacture or sale. Not saying that it might not happen, but it didn't happen wit my stock.

[Cubdriver]

Thank you very much to everyone that applied. How do I ensure an email notification when someone responds to my post?

I think the following is what you need to do:

Click on your profile, then hit the 'modify proflie' tab above the summary, and select 'notifications' from the pull down menu.

Check 'turn notification on when you post or reply to a topic' (2nd one)

Select frequency of notification - instantly, instantly for first new post only, daily, or weekly (I think you want one of the first two)

Then select what you want to be notified of - I expect you'll want either 'replies and moderation' or 'replies only'.

Hope this helps

-Pat