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6094 Views 8 Replies Latest reply: Jul 23, 2010 2:38 AM by enrico.migchels RSS
AllanGreen Level 1
AllanGreen
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Jun 10, 2010 4:52 AM

Electrolytic capacitor shelf life?

Hi everyone,

 

I wonder if anyone has any idea (or even a gut feeling!) what the expected shelf life of a "typical" electrolytic capacitor might be?  Approximately 5 years ago (cannot remember exactly) I purchased a bag of ten 1000uF 25V pcb capacitors (Farnell 921 270) and when I came to use one every single capacitor had "blown" (some even leaking electrolyte.)  They had been stored in normal office conditions (and were still in the bag in which they had been supplied.)

 

Farnell were unfortunately not interested in replacing them, but I'm very glad that they never actually got into service where presumably they would have failed even sooner. In another life I repair vintage valve radio receivers; while some electrolytics do fail after 50 years of use, many definitely survive!  Is this the price of miniaturisation?  Obviously there are definite implications for the stock levels I should be attempting to maintain if this is commonplace.

 

I'd be fascinated to hear any comments other users may have!

 

Allan Green

 

 

PS I've just found the details for these capacitors via the Farnell Australia site!  They are "Multicomp High Temperature MCRH series general purpose electolytics" and apparently have a guaranteed lifetime of 2000 hours at 105 deg C.  I wonder how long it was before mine failed?!  Maybe I should have checked them every six months!

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  • enrico.migchels Level 4
    enrico.migchels
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    1. Jun 10, 2010 5:11 AM (in response to AllanGreen)
    Re: Electrolytic capacitor shelf life?

    Hi Allen,

     

    In professional production processes shelf life for elcaps is limited to 3 years. It might also be the solderability which is an issue and not the deformation only. In practice I have no (or hardly) any failures due to the deformation of the oxide in an elcap. If you want to be on the safe side (but who has the time?) you have to apply the working voltage to the device and limit the inrush current (via a current source or resistor). After a while the leakage current of the device is drastically reduced. This is one of the reasons that I measure input power in standby mode of a product after several hours.

     

    Guaranteed lifetime or basic lifetime of 2000 hours is not bad. You can calculate useful lifetime with your application conditions (ripple current and ambient temperature) and with a given use of the device (x hours on / x hours off) you get a lifetime calculation. The elcaps are most of the time the first to fail, so in fact you can calculate the lifetime of the whole product. Using Multicomp capacitors is not my first choice. You will be unsure of the specification of the device. Supplier as Rubycon, Lelon and others give formulas and equations to calculate for useful lifetime (with a certain guarantee)

     

    Best regards, Enrico Migchels

  • AllanGreen Level 1
    AllanGreen
    Currently Being Moderated
    2. Jun 10, 2010 5:29 AM (in response to enrico.migchels)
    Re: Electrolytic capacitor shelf life?

    Thanks Enrico,

     

    Your 3 year figure is certainly useful guidance - I'd missed on this tip somehow!  If 2000 hours "isn't bad" though, I'm a little worried that a product (working within ratings) is only guaranteed for less than 3 months.  It is obviously a harsh world out there. 

     

    I am familiar with the idea of refoming capacitors if left unused for a long time (especially in repair of vintage electronics), and it certainly does improve leakage currents to a fraction of their original value.  In the case of my capacitors however I suspect a production fault, reforming these every so often seems unlikely to have prevented can rupture.  I cannot help wondering whether it is the same problem (rumoured to be related to industrial espionage of a component in the electrolyte formula) which caused the failure of thousands of PC motherboards a while ago.

     

    Thanks again for taking the time to answer,

     

    Allan

  • enrico.migchels Level 4
    enrico.migchels
    Currently Being Moderated
    3. Jun 15, 2010 4:09 PM (in response to AllanGreen)
    Re: Electrolytic capacitor shelf life?

    Hi Allen,

     

    2000 hours load life is under maximum rating (current, temperature). As your application is certainly less, the lifetime jumps to normal values (many years). However you have to measure and calculate this lifetime figure. I recently had NCC elcaps in my design which could not meet the spec on ESR (they were copycats of the original products). These copycats will not meet the desired lifetime!

     

    best regards, enrico migchels

  • ray_shatzel Level 2
    ray_shatzel
    Currently Being Moderated
    4. Jun 15, 2010 4:42 PM (in response to AllanGreen)
    Re: Electrolytic capacitor shelf life?

    Hi Allen,

     

    The "lesson learned" here is stick with known names. Multicomp is a "generic" in house brand - not unlike generic food in the grocery store.

     

    Stick with well known manufactures that back their product - they cost a little more but you won't end up throwing away parts in a few years or worse RE-installing them!

     

    I also enjoy repairing & restoring electronic equipment for my hobby (amateur radio) too. It is amazing to see how many of those old caps spring back (reform) to life! In most cases though I change them out when they getb past 30-40 years - where they are critical (example: B+ supply).

     

    Enjoy

    Ray

  • jfurman@ocs.net Level 1
    jfurman@ocs.net
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    5. Jun 18, 2010 9:20 PM (in response to AllanGreen)
    Re: Electrolytic capacitor shelf life?
    This wikipedia article discusses a particular failure cluster, I believe related to poor industrial espionage where the secret formula is stolen, but one of the ultra secret ingredients is left out.
  • robprof Level 1
    robprof
    Currently Being Moderated
    7. Jul 18, 2010 9:09 AM (in response to AllanGreen)
    Re: Electrolytic capacitor shelf life?

    Hello Allen,

     

    Several years ago there was a spate of bad capacitors on the market but I'm surprised that Farnell sold any. If the caps have failed during storage (assuming normal room temperatures) they were definately of faulty manufacture. The electrolyte must have gassed, suggesting there was no depolariser in the formula!

    I design and service a wide range of audio equipment including many vintage types. I am always surprised how certain makes of electrolytics still function perfectly after 20 years or more of use. On test their value and leakage current are still well whithin spec! Nichicon, Kemet, Nippon-chemi-con, Elnet are the makes that spring to mind. On the other hand there are well known makes that always show signs of deterioration after this period of time.

     

    Rob Beales

    Amplabs

  • enrico.migchels Level 4
    enrico.migchels
    Currently Being Moderated
    8. Jul 23, 2010 2:38 AM (in response to robprof)
    Re: Electrolytic capacitor shelf life?

    Hi,

     

    Last week I was tortured again with an flood of bad capacitors. It is not enough to use only the well-known brands; you really have to secure the logistic-channel. If you buy for people who buy from people.... you might end up with unreliable and inferior components. An extra problem is that will not get the technical support you need to the root cause.

     

    best regards, Enrico Migchels

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