Key points of this definitive article on shelf life of lytic caps. (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.823.6133&rep=rep1&type=pdf)
There is not a set shelf life beyond which an electrolytic capacitor is guaranteed to fail. In one study, electrolytic capacitors were verified to perform adequately after 30 years of storage. Shelf Life is 16yrs with periodic reforming in accordance with manufacturers’ standards, otherwise 5yrs or manufacturer’s recommended shelf life. Can electrolytic capacitors, typically greater than 1 inch in length and diameter used in power supplies, should have a shelf life of about 20 years, based upon storage temperatures. High storage temps are to be avoided leads to greater dry out of electrolyte. Radial and axial lead electrolytic capacitors should have a shelf life greater than the can lytics.
Accelerated aging tests have shown that capacitors show a small decrease in
capacitance but proportionately larger increases in ESR and DC leakage current. The increase in ESR was on the order of 65% and DC leakage a magnitude of over 400%. As ESR and DC leakage goes up, the resistive heating of the capacitor in service increases which may cause rupture of the seals and blow up. Improved vapor seals limit the evaporation of the electrolyte and as long as there was enough electrolyte left in the capacitor, the capacitor could reform itself.
In general, the reforming process consists of applying voltage to the capacitor without exceeding the specified leakage current. The voltage is increased up to the rated value using a Variac, or light bulb limiter. Panasonic recommends applying rated voltage across a 1Kohm resistor for 30 minutes.
I hope you find the info useful
Nicolas
There is not a set shelf life beyond which an electrolytic capacitor is guaranteed to fail. In one study, electrolytic capacitors were verified to perform adequately after 30 years of storage. Shelf Life is 16yrs with periodic reforming in accordance with manufacturers’ standards, otherwise 5yrs or manufacturer’s recommended shelf life. Can electrolytic capacitors, typically greater than 1 inch in length and diameter used in power supplies, should have a shelf life of about 20 years, based upon storage temperatures. High storage temps are to be avoided leads to greater dry out of electrolyte. Radial and axial lead electrolytic capacitors should have a shelf life greater than the can lytics.
Accelerated aging tests have shown that capacitors show a small decrease in
capacitance but proportionately larger increases in ESR and DC leakage current. The increase in ESR was on the order of 65% and DC leakage a magnitude of over 400%. As ESR and DC leakage goes up, the resistive heating of the capacitor in service increases which may cause rupture of the seals and blow up. Improved vapor seals limit the evaporation of the electrolyte and as long as there was enough electrolyte left in the capacitor, the capacitor could reform itself.
In general, the reforming process consists of applying voltage to the capacitor without exceeding the specified leakage current. The voltage is increased up to the rated value using a Variac, or light bulb limiter. Panasonic recommends applying rated voltage across a 1Kohm resistor for 30 minutes.
I hope you find the info useful
Nicolas
Whatever, an academic full of ****.
The rubber of cheap caps deteriorates sitting on the shelf or used.
Don't believe me, look at old tires.
The seal doen't fail until after it is pressureized a few times by heat of use, and the water evaporates out,
Don't believe me, buy an organ grandma played a couple of times the year she bought it, then got discouraged and didn't fool with it until she died. Thirty years later, average life after a newbie buys one and plays it a lot, 8 weeks.
I had an amp I put a new B+ cap in 1982, played it an hour, got discouraged at the lack of new output tubes available, put it away and bought a piano. I bought new tubes 2013, put them in , reformed the caps, played it two hours, great power. Next day, pffft, blew the fuse, big puddle in the bottom of cap slime. Cap failed with three hours on it.
The rubber of cheap caps deteriorates sitting on the shelf or used.
Don't believe me, look at old tires.
The seal doen't fail until after it is pressureized a few times by heat of use, and the water evaporates out,
Don't believe me, buy an organ grandma played a couple of times the year she bought it, then got discouraged and didn't fool with it until she died. Thirty years later, average life after a newbie buys one and plays it a lot, 8 weeks.
I had an amp I put a new B+ cap in 1982, played it an hour, got discouraged at the lack of new output tubes available, put it away and bought a piano. I bought new tubes 2013, put them in , reformed the caps, played it two hours, great power. Next day, pffft, blew the fuse, big puddle in the bottom of cap slime. Cap failed with three hours on it.
Last edited:
The article is based on the authors´s review of all the literature on the subject for his thesis. I agree long term storage especially in a hot environment will cause drying out of the electrolyte which will cause higher resistance (ESR) and DC current leakage while capacitance may measure NORMAL !!. Soon after its put into use the heat from the increased ESR and DC leakage causes increase pressure and failure of the seals. Its important to note that Capacitance may measure pretty good so its not as reliable a measure of impending failure as is a higher ESR.
My looking into this is was because I have a Mackie 32-8 mixing console which after 1 year of use got put into metal shed storage under Florida sun since 1999. Was planning to bring it out of storage and put it into use but suspect there may be fireworks because of the time and conditions of storage. Probably be best to reforms the caps by slowly increasing voltage pull out a board and test it´s capacitors for ESR if they pass then can presume the rest are also OK. It would be a PITA to do so those Mackies are notoriously difficult to work on.
Nicolas
My looking into this is was because I have a Mackie 32-8 mixing console which after 1 year of use got put into metal shed storage under Florida sun since 1999. Was planning to bring it out of storage and put it into use but suspect there may be fireworks because of the time and conditions of storage. Probably be best to reforms the caps by slowly increasing voltage pull out a board and test it´s capacitors for ESR if they pass then can presume the rest are also OK. It would be a PITA to do so those Mackies are notoriously difficult to work on.
Nicolas
Shelf life is 1 year in a typical industrial setting. Older caps are discarded, and rightfully so.
The reality is somewhat more nuanced: in fact, all depends on the manufacturing (and that doesn't equate to the manufacturer, I'll explain later).
E-caps can be made to last forever, even under harsh conditions, or can degrade under light duty or even no duty at all in a matter of years.
Reputable Japanese or German manufacturers like Rubycon or Siemens have produced practically eternal components (on the scale of a human life), but others, like ROE, many British or US sources tend to adhere to the "programmed obsolescence" concept.
I have a stash of NOS caps of good origins, which I keep for really important projects, where failure is not an option.
I do not even care to reform them, they are operational and ready from second 1.
Here is an example of project where I used my strategical reserve:
http://www.diyaudio.com/forums/power-supplies/301262-external-autonomous-soft-start.html#post4929832
Basically, I know that the Siemens and Rubycon caps I used will outlive me, and by some margin.
The same could not be said of most of the contemporary production (note that these have been stored for around 45yrs, without ever being used [not under harsh conditions, just tempered Europe]).
These caps are physically huge by today standards, but otherwise they have remarkable performances, on the par with the best of present production, except solid polymer types (for which questions remain about their very long term ageing qualities).
If you opt for some crap brands (don't ask for names!), relatively recent components can litterally melt down after only a few years of shelf life.
The Philips production is in-between: some series are awful, but the axial type shown in the example (also dating back from the early seventies) is perfectly OK, and will stay so unless (very) severely abused
E-caps can be made to last forever, even under harsh conditions, or can degrade under light duty or even no duty at all in a matter of years.
Reputable Japanese or German manufacturers like Rubycon or Siemens have produced practically eternal components (on the scale of a human life), but others, like ROE, many British or US sources tend to adhere to the "programmed obsolescence" concept.
I have a stash of NOS caps of good origins, which I keep for really important projects, where failure is not an option.
I do not even care to reform them, they are operational and ready from second 1.
Here is an example of project where I used my strategical reserve:
http://www.diyaudio.com/forums/power-supplies/301262-external-autonomous-soft-start.html#post4929832
Basically, I know that the Siemens and Rubycon caps I used will outlive me, and by some margin.
The same could not be said of most of the contemporary production (note that these have been stored for around 45yrs, without ever being used [not under harsh conditions, just tempered Europe]).
These caps are physically huge by today standards, but otherwise they have remarkable performances, on the par with the best of present production, except solid polymer types (for which questions remain about their very long term ageing qualities).
If you opt for some crap brands (don't ask for names!), relatively recent components can litterally melt down after only a few years of shelf life.
The Philips production is in-between: some series are awful, but the axial type shown in the example (also dating back from the early seventies) is perfectly OK, and will stay so unless (very) severely abused
Bad advice. Cap reforming needs to be current limited. A simple way to achieve this is to connect to the rated voltage via a high value resistor (100k?) and monitor the voltage. If it rises fairly quickly then swap to a slightly lower value resistor. Repeat as necessary until the cap either won't increase in voltage (then throw it away) or it can happily sit at rated voltage with a small resistor (maybe the 1k they suggest).nicoro said:
Panasonic´´srecomendations
From the badcaps forum more material regarding Panasonics recomendations
"As per the Panasonic HFQ series datasheet again, the series resistors can all be 1 KOhm. However, according to some tests I did, it may be better to use higher resistances if the caps to be reformed are very old (as in, 10+ years in storage) or if they were used with a much lower voltage than their rated voltage (again, motherboard CPU caps should come to mind here), otherwise they may develop and internal short-circuit. For my reformer, I used mostly 10 KOhm resistors (but also tried a few 15 KOhm and 47 KOhm ones). Just about anything between 1 KOhms and 100 KOhms will work, since this is nowhere near exact science. From my experiments, however, the further you go above 10 KOhms, the longer it takes for the caps to charge (especially for ones over 1000 uF), and this will slow down the reform process or won't reform the capacitors to the maximum voltage you selected with the source.
With that being said, if you find that some of your caps have not reached 90% of the source voltage after 30 minutes of reforming, then one of the following could be happening:
(1) The series resistor has too large of a resistance for the capacitor it is reforming
(2) The cap is possibly excessively leaky
(3) A combination of the two above
The best solution for this would be to lower the resistance of the series resistor. However, do NOT use less than 1 KOhms (except possibly for very large caps, like 400V, 500 uF… or 25V, 4700 uF). If the cap still does not reach 90% of the source voltage after this, you should test the cap's leakage current and compare to datasheet maximum (see Leakage Current thread). And if the cap shows only a few mV to 1V across its terminals after a minute or so of reforming – STOP! The capacitor has likely become short-circuited internally. Depending on your multimeter, you *may* be able to verify this by measuring the resistance. But don't count on it. I had a few caps short-circuit, and while some read as low as just several Ohms, one read 1.8 KOhms (which is far from a short-circuit… but if you put this cap in a device and apply power, it will likely short almost immediately"
Nicolas
From the badcaps forum more material regarding Panasonics recomendations
"As per the Panasonic HFQ series datasheet again, the series resistors can all be 1 KOhm. However, according to some tests I did, it may be better to use higher resistances if the caps to be reformed are very old (as in, 10+ years in storage) or if they were used with a much lower voltage than their rated voltage (again, motherboard CPU caps should come to mind here), otherwise they may develop and internal short-circuit. For my reformer, I used mostly 10 KOhm resistors (but also tried a few 15 KOhm and 47 KOhm ones). Just about anything between 1 KOhms and 100 KOhms will work, since this is nowhere near exact science. From my experiments, however, the further you go above 10 KOhms, the longer it takes for the caps to charge (especially for ones over 1000 uF), and this will slow down the reform process or won't reform the capacitors to the maximum voltage you selected with the source.
With that being said, if you find that some of your caps have not reached 90% of the source voltage after 30 minutes of reforming, then one of the following could be happening:
(1) The series resistor has too large of a resistance for the capacitor it is reforming
(2) The cap is possibly excessively leaky
(3) A combination of the two above
The best solution for this would be to lower the resistance of the series resistor. However, do NOT use less than 1 KOhms (except possibly for very large caps, like 400V, 500 uF… or 25V, 4700 uF). If the cap still does not reach 90% of the source voltage after this, you should test the cap's leakage current and compare to datasheet maximum (see Leakage Current thread). And if the cap shows only a few mV to 1V across its terminals after a minute or so of reforming – STOP! The capacitor has likely become short-circuited internally. Depending on your multimeter, you *may* be able to verify this by measuring the resistance. But don't count on it. I had a few caps short-circuit, and while some read as low as just several Ohms, one read 1.8 KOhms (which is far from a short-circuit… but if you put this cap in a device and apply power, it will likely short almost immediately"
Nicolas
As long as we are on this subject.... Where can I find replacements for my Mallory CGS293U080X6L3PH capacitors? No longer made, I'm sure I need a cross reference to something new that has not sat on the shelf. 🙂
Everybody on these threads mixes up electrolyte-aluminum life, and sealant life.
Shelf life is so short because caps go in pick and place machines, then are hammered by full rated voltage with unlimited current immediately after turn on. After they leave the factory, and the shelf life expires, the chemical bond deteriorates and they DO need reforming gently before hitting with max voltage unlimited current. As an individual I often buy distributor flagged "old" caps at a discount, typically a year old, and then reform them with my DVM ohms scale before installing. This has worked even on the dozens of 450 v caps I've installed in tube circuits, despite the DVM only charging up to 2 v.
Sealant life depends on sealant initial quality, the action of ozone oxygen in the air, and heat. A cap sitting on the shelf can have an elastomeric seal that is cracked, without ever losing a drop of water, because there was no heat to pressurize it. Caps with chemically stable seals, as epoxy (there have been a few lines of such) the seals do not age on the shelf. when used a cracked seal cap or dry rotted seal cap, when heated up by use, outgasses and the life is limited by how much reserve water was packed into the case. Bigger resevoir size is often reflected in service life, but nobody discloses what sealant they are using. For some experience, look at tires. there are lots of them with 50 miles on them that are useless now because they won't hold air.
Manufacture name IMHO doesn't guarentee the type of seal used. Some brands available have 10000 hr service life lines, also 500 hour service life lines. Many **** brands don't even quote a service or shelf life. I've found grey or blue CDE caps installed as late as the mid eighties to be universally trash by now, but they sold a line of green epoxy sealed caps that David A has said he never finds defective or high ESR in guitar amps containing them.
There was also a Sprague epoxy line, so mythical I've never seen one.
I also find, many of the caps in supplies blowing breakers fuses or whatever, do not have comically high ESR's, now that I have an ESR meter. The meter was a waste of $100. I replace caps based on 1 bad performance of circuit + 2 date of manufacture, IMHO. One goes bad, I do all of them. Now conveniently the orientals have shortened the manufacture date marking to one digit year, so one has to replace everything all the time on a defective circuit to produce a quality repair. From the number of boards I find with used caps tacked on above the blown old ones, or caps replaced with ones older than the date of the board manufacture, the idea of making a quality repair in the home entertainment or bar band repair industry is also mythical .
Shelf life is so short because caps go in pick and place machines, then are hammered by full rated voltage with unlimited current immediately after turn on. After they leave the factory, and the shelf life expires, the chemical bond deteriorates and they DO need reforming gently before hitting with max voltage unlimited current. As an individual I often buy distributor flagged "old" caps at a discount, typically a year old, and then reform them with my DVM ohms scale before installing. This has worked even on the dozens of 450 v caps I've installed in tube circuits, despite the DVM only charging up to 2 v.
Sealant life depends on sealant initial quality, the action of ozone oxygen in the air, and heat. A cap sitting on the shelf can have an elastomeric seal that is cracked, without ever losing a drop of water, because there was no heat to pressurize it. Caps with chemically stable seals, as epoxy (there have been a few lines of such) the seals do not age on the shelf. when used a cracked seal cap or dry rotted seal cap, when heated up by use, outgasses and the life is limited by how much reserve water was packed into the case. Bigger resevoir size is often reflected in service life, but nobody discloses what sealant they are using. For some experience, look at tires. there are lots of them with 50 miles on them that are useless now because they won't hold air.
Manufacture name IMHO doesn't guarentee the type of seal used. Some brands available have 10000 hr service life lines, also 500 hour service life lines. Many **** brands don't even quote a service or shelf life. I've found grey or blue CDE caps installed as late as the mid eighties to be universally trash by now, but they sold a line of green epoxy sealed caps that David A has said he never finds defective or high ESR in guitar amps containing them.
There was also a Sprague epoxy line, so mythical I've never seen one.
I also find, many of the caps in supplies blowing breakers fuses or whatever, do not have comically high ESR's, now that I have an ESR meter. The meter was a waste of $100. I replace caps based on 1 bad performance of circuit + 2 date of manufacture, IMHO. One goes bad, I do all of them. Now conveniently the orientals have shortened the manufacture date marking to one digit year, so one has to replace everything all the time on a defective circuit to produce a quality repair. From the number of boards I find with used caps tacked on above the blown old ones, or caps replaced with ones older than the date of the board manufacture, the idea of making a quality repair in the home entertainment or bar band repair industry is also mythical .
Last edited:
This is a very interesting topics!! I think your point on the seal sounds logical. But your example using the tire rubber is a little misleading since it makes people think that the same rubber used in tires is also used for the caps, is that true? Or you just using it as an example?
I am no expert in caps but I do conduct research for a living. IMHO, E-caps can "die" due to external factors (e.g. the seal or case is compromised by the environment that lead to mechanical failure), or internal factors ( the chemical inside underwent some irreversible reactions over a long period of time and its charge holding capacity is compromised). The damage caused by external factors is not difficult to understand. However, are there any published data on the cap-seal stability studies (under control environment of course) or are we just making "reasonable guesses"?
I saw suggestions on this thread on how to reform E-caps. My logical deduction is that reforming is developed to repair the "damage" to E-cap caused by internal factors. However, there seems to be different schools of thoughts on conducting reforming. I am very curious to learn about what kind of electrochemistry is happening during reforming. Only when one understands the chemistry that proper assessment on the reforming process be assessed. Can anyone point me to any scientific papers regarding this aspects?
Regards,
These will get you started.
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf)
https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/DMF0000COL42.pdf
Nicolas
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf)
https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/DMF0000COL42.pdf
Nicolas
- Status
- Not open for further replies.