Cheap electrolytic caps - reliability

[Miyuki]

Hi folks,

I have a question, are cheap electrolytic caps really bad or are they just commonly misused (exceeding ratings fairly)
I'm talking about capacitors with datasheets from common distributors, but unknown brands (which cost like 1/4 of Panasonic or other brands)
For example if they say 5000h at 105°C and rated current can these values be believed ?
Do good brands work longer than specified Or are they more commonly used in good designed products with proper rating ?

[tkamiya]

I have not taken data recently but one certain name brand manufacturer used to rank its products, sold the best one under its own brand name, second for OEM, and the rest for "dumpster".

I would think, if it does not bear company's name or does but it is an obscure company, there is no intensive to make them reliable and long lasting.  Only motivation is to sell as many as one could, as fast as one could. 

I have a packages of cheap parts to experiment with and use in emergencies.   I check them against calibrated sources to check its value before putting them in a circuit.  If it is anything I care, or a final product, I buy name brand from top shelf companies.

[RobK_NL]

I'm not even going to bother to find out.

The products I design and build are supposed to last. Buying 'no-name' capacitors might save me a few euros per year, but a single field return because of a prematurely failed component will cost me lots more. Not to mention the cost of losing my reputation.

If your business is consumer electronics with numbers >100k per month, it might be a different story.

[EHT]

I wonder about how to translate the lifetime figures. Even the highest rated ones still do not represent a long life for equipment which may be operated 24/7 (i.e. 8760h / year), such as a UPS. The figures quoted are at the highest temp but they never say how long the caps are rated for at lower temps e.g. < 50C. I select those with the highest lifetime given the other constraints, but I'm not designing commercial products.

[bd139]

I had some ChongX capacitors arrive a while ago covered in exploded capacitor fluff. Looks like one blew up in the factory somewhere and they just chucked it in a bag and shipped it.

Ergo, I buy Panasonic now.

[wraper]

If they are general purpose series, don't experience high ripple current and don't work at high temperatures, usually they'll last just fine. Though my advise is to never use LOW ESR series and/or under high stress.

[wraper]

Do good brands work longer than specified Or are they more commonly used in good designed products with proper rating ?

Known brand is sort of guarantee of consistency and that they won't start failing unexpectedly.

[cdev]

How does one rate unknown or partially known brands? For example, I am familiar with Elna and Rifa but what about Wima or (lightning bolt sign)Sc on a 105 C 6.3 v electrolytic.

There are a lot of brands I have some parts from whom I have never heard of (I buy grab bags of parts, which are a great deal in terms of quantity, and I think the quality is often quite good too, but how can I look up parts, particularly electrolytics, when Ive never heard of the manufacturer?) Does anybody compile info on reliability?

[wraper]

Wima or (lightning bolt sign)Sc on a 105 C 6.3 v electrolytic.

Wima does not make electrolitic capacitors. SHIANG CHEN seem to be okayish if general purpose and not stressed. I would not use them myself though. For me it would be Jamicon, samxon, samwha, yageo, samyoung below which I would not go.

[Miyuki]

Wima does not make electrolitic capacitors. SHIANG CHEN seem to be okayish if general purpose and not stressed. I would not use them myself though. For me it would be Jamicon, samxon, samwha, yageo, samyoung below which I would not go.

Samxon GT series look nice
Also Samwha WL just with shorter rated life

They have decent reputation on forums

And they are also cheapest low esr/high ripple at shop if I don't count Elite brand which have terrible reputation 

[wraper]

And they are also cheapest low esr/high ripple at shop if I don't count Elite brand which have terrible reputation

Actually Elite are quite decent IME. You'll have a hard time finding of them mentioned going bad. FWIW Samxon and Samwha made their share of crap as well. Such as GF and WB series respectively.
Edit, actually Elite is used by Dell quite a lot.

[wraper]

Also I would consider using Lelon and Ltec. Quite old brands and IME repairing stuff they were reliable.

[splin]

I wonder about how to translate the lifetime figures. Even the highest rated ones still do not represent a long life for equipment which may be operated 24/7 (i.e. 8760h / year), such as a UPS. The figures quoted are at the highest temp but they never say how long the caps are rated for at lower temps e.g. < 50C. I select those with the highest lifetime given the other constraints, but I'm not designing commercial products.

The manufacturer should publish this info in the datasheet or a technical bulletin/application note. Generally the lifetime doubles for every 10C reduction in temperature. The ripple current through the capacitor's ESR will dissipate power, heating the capacitor above ambient. There is a useful calculator here where you can estimate lifetime based on temperature, ripple current, case dimensions etc.:

https://www.illinoiscapacitor.com/tech-center/life-calculators.aspx

[Miyuki]

Have someone experience with Polymer caps ?
For example that Elite one UPE Series will offer better ripple current than classic equivalent for same or lower price
And expected lifetime is also higher for them

[BravoV]

The manufacturer should publish this info in the datasheet or a technical bulletin/application note. Generally the lifetime doubles for every 10C reduction in temperature. The ripple current through the capacitor's ESR will dissipate power, heating the capacitor above ambient. There is a useful calculator here where you can estimate lifetime based on temperature, ripple current, case dimensions etc.:

https://www.illinoiscapacitor.com/tech-center/life-calculators.aspx

Thanks for the link.

Intrigued, I did play abit for the polymer type, and set the ambient temp say like 60 or 70 C, surprisingly that thing will work for few generations. 

[wraper]

Have someone experience with Polymer caps ?
For example that Elite one UPE Series will offer better ripple current than classic equivalent for same or lower price
And expected lifetime is also higher for them

Generally they are very reliable as long as not overstressed. Their failure mode is usually going short.