Electronics > Power/Renewable Energy/EV's

reform old electrolytic capacitor

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tiago1986:
Please can any specialist help me I've read a lot about the subject but I still have doubts electrolytic capacitors of any brand, manufactured in the early 90's (31 years old) and mounted in electronic circuit, need reform after what maximum interval of time? the only reform I do doesn't use a resistor, just connect the device to the power with the plug

Shock:
They mean by reforming, limiting the current on purpose to allow the capacitor to gracefully lower it's internal leakage value back into tolerance.

Switching the device on from cold when it's been left unused for a decade is not reforming but if you use the device every 6 to 12 months it should reduce the chance of failure soon after power up.

What it won't stop is poor quality caps physically leaking, falling out of tolerance or attrition due to the natural end of life of that capacitor series. So often it's easier and more cost effective just to replace old capacitors if you plan to keep the device rather than checking them one by one.

The other way is look up if the device is being recapped by others or mentions of problems with that brand/series and age of cap.

tiago1986:
why some electrolytic capacitor manufacturers say 2 years and others 3 years? their suggestion is for new unused electrolytic capacitors and were from the electronic circuit and a reputable brand? is my case different?

Shock:
The storage period before reforming doesn't indicate quality or reliability, different brands and series will have different specifications. The capacitor might not outright fail if used past that 2-3 year point, just a greater chance of it degrading in performance if not reformed first.

When the device is used in normal operation the capacitors self heal. So as I said use the device periodically or replace the capacitors outright you are worried. Reform capacitors you have had sitting around before using them in a circuit/device (if you want to get the best life possible).

Faringdon:

--- Quote ---Please can any specialist help me I've read a lot about the subject but I still have doubts electrolytic capacitors of any brand, manufactured in the early 90's (31 years old) and mounted in electronic circuit, need reform after what maximum interval of time? the only reform I do doesn't use a resistor, just connect the device to the power with the plug

--- End quote ---
Yes, reform after  2 years.

If you dont know, get one cap thats been in store for 3 years...put a small current sensor in series with it.......suddenly connect it to 0.9* rated vout...........note the leakage current, and its duration, if its too big, then reform them with the  1k(?) resistor.

But yes, i always wonder how anyone can tell how old a capacitor is...the manufacture data is not printed on them.

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