Alum. Electrolytic capacitor shelf life

Discussion in 'General Electronics Chat' started by mcgyvr, Dec 7, 2012.

  1. mcgyvr

    Thread Starter AAC Fanatic!

    Oct 15, 2009
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    Just got a datasheet from an aluminum electrolytic cap (75V 23k uF) and noticed it showed shelf life as 500 hours @85 deg C.. Does that seem crazy low to anyone else? I've seen others "claim" 3 years.

    Do people routinely energize/reform caps on the shelf to extend their shelf life?
    The caps could be on our shelves for a few months at most usually and I'd HATE to have to power them up every 20 days or so..
     
  2. takao21203

    Distinguished Member

    Apr 28, 2012
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    I have some Mitsubishi el. caps here from 1986 which still work fine.

    It depends on the brand, and how much current flows through them, and the temperature.

    if possible don't exceed 50C, or they will dry out easily.

    There are also caps designed for 105C which are better for higher temperatures.

    CFLs often only live for 6 months to a year, if there is not enough airflow. As far as I know this is due to problems with their filter cap. drying out. I have seen CFLs failing after only a few months, and then after 1/2 year to one year most failed, except one Phillips CFL type.

    High currents at the limit will cause bulging and venting statistically, not all caps regularily, but it occurs. Highly depend on the brand.

    High temperature is the worst that can happen to an electrolytic cap.
    Otherwise they can live for decades.

    I have even two 3300uF Siemens el. caps here from 1981, which still produce very powerful sparks, and are still good for PSU filtering.
     
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  3. mcgyvr

    Thread Starter AAC Fanatic!

    Oct 15, 2009
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    Thank you for your response.
    Just talking "shelf life" here though.
    25 deg C ambient
    0 VDC
    0 current

    As I'm looking, I've been finding much more reasonable times when the published storage temps are lower.. 30000 hours @ 40 deg C.. seems MUCH more realistic to me. Just wasn't aware there was that much of a decrease in shelf life based on ambient temps.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I have 30 year old caps that work fine.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I doubt the spec is for "storage, non-operational," but for active use. They are trying to tell you this cap ain't worth poop even under very benign conditions of use. And before you start screaming about junk parts hey they told you and in some products that lifetime is just fine. Take a musical greeting card you play once or twice and toss away.

    As far as I know "older" caps, such as you find in an antique piece of tube equipment, need a reforming period when turned on after a long (years, decades) storage time, so the electrolyte can undergo some process besides "explode." This is best done with a variac, slowly increasing the input voltage over a period of several days.
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    I have an HH Scott FM stereo that is about 48 years old and it still works perfectly.
    My oscilloscope is about the same age and it also still works perfectly.
    Same for my signal generator.
    They do not have parts made in China!
     
  7. crutschow

    Expert

    Mar 14, 2008
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    It may be that unpowered electrolytics at high temperature have a shorter life then if they are powered.
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I bet your shelves are a lot cooler than 85° C (185° F.) Still, I agree that 500 hours is ridiculous.
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That's an operating life spec, not a shelf life spec.

    And 500 hours at 85'C is not bad for a part whose absolute max operating temp is 85'C.

    Try holding something that is 85'C in your hand and see how long you can tolerate it... I bet it's in the milliseconds! ;)
     
  10. ramancini8

    Member

    Jul 18, 2012
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    That is shelf life at an ambient temp. of 85 C! As temperature reduces shelf life increases, so the shelf life of that cap at 25 C is probably years. Heat dries out the electrolyte, so high temp storage shortend life.
     
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