On 09.07.25 22:09, Viesturs Lācis wrote: > pirmd., 2025. g. 7. jūl., plkst. 19:17 — lietotājs gene heskett
> (< ghesk...@shentel.net >) rakstīja: > > Electrolytic caps should always be used at 90% of rated voltage or even > > higher., a 16 volt cap used in a 3.3 volt circuit has a failure time > > generally under a year. The under voltage allows the cap to "deform" > > losing capacity in the process. > > Thank you for this little piece of information!!! When choosing caps > for rectifiers I did choose such a voltage to have extra margin. It > just felt better. Now it turns out that it was bad and unjustified > choice. Viesturs, retired electronics engineer here, who has done it your way for four decades. In our Siemens design lab, the rule for 25 year minimum service life in Telecommunications equipment was "Never specify an electrolytic capacitor to operate above half its rated voltage." That was based on sheaves of reliability test data provided by a Munich department which was there to protect the name & the products. Even as a teenager, back in the late 1960s, I used the technician's trick of gently reforming an old electrolytic with a multimeter on ohms range, apparently connected reverse polarity, because Ohms put -3 Vdc on the +ve meter lead. The needle gave an indication of reforming progress, as leakage diminished. Once minimal at 3 volts, it was safe to apply higher voltage. (To wit: 3v will substantially reform a 100v electrolytic's dielectric in a minute or two.) That worked for electrolytics which had lain for a decade or more in unpowered equipment, i.e. *zero* voltage, so "failure in a year" is not real-world in my half century of experience. I suggest that it is applying full working voltage to a high voltage electrolytic, after years powered down, without first reforming the dielectric, which does them in. That and drying out - the seals aren't perfect. That said, I have had a bunch of cheap consumer grade electrolytics lose capacitance over 40 years - but in service near full rated voltage. Erik _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
