Never used electrolytics - how old is too old? - Page 1
Forum section: electronics / general

author: CaptainBucko
author_rank: Regular Contributor
timestamp: April 25, 2025, 12:57:25 am
content: Found a box of about 100 x Nichicon(correction Jamicon) 10,000uF 100v Electros. All were brand new and had some foil keep all terminals shorted together. Some newspaper was used for packing, with a print date of Oct 1987. Are these going to be junk or still useful for hobby projects?I don't have any plans for operating near the 100v limit, probably 50v at most. I did find a datasheet but the shelf life statement didn't make sense to me. One of them measured 10700uF on my DMM. So how old is too old when they have never been in use?

author: rsjsouza
author_rank: Super Contributor
timestamp: April 25, 2025, 01:09:47 am
content: Not Nichicon, but Jamicon.Older capacitors can be ok if you do some reforming and thorough testing for leakage, capacitance and, naturally, physical integrity - i.e., they don't explode in your face.I personally used older capacitors in specific applications where any damage would not have a severe impact in the integrity of the circuit. If you are dealing with 100V but in applications with severe current limiting, the possibility of catastrophe is likewise limited as well.

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2025, 04:42:37 am
content: If they are physically larger, then they should be fine. Smaller aluminum electrolytics dry out more quickly because their volume to leakage is smaller.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 25, 2025, 04:55:38 am
content: I'd take a few, maybe 5 or 10 from various locations in the box and reform them at a few mA up to 100V and then test them to get a general idea of how good they are.As long as the capacitance, leakage and dissipation is within spec, and ESR is reasonable by rule of thumb, they are probably ok to use.If any of the sample you test is bad, then the batch is suspect and each capacitor would require individual testing before use (I would reform them all in any case, the oxide layer would be pretty thin by now...).I would avoid using them in mission critical applications in any case.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 25, 2025, 01:32:13 pm
content: It is expected the capacity toincreasewhen electrolytic capacitors are left unused for a very long time.The idea is that there is a thin layer of oxide that is formed from factory, and the thickness of that layer dictates both the capacity and the maximum supported voltage of the capacitor. With time, that layer of oxide naturally dissolves (partially) in the existing electrolyte inside the capacitor. The thinner the oxide layer, the more capacitance, but at a lower max supported voltage.The good part is that the oxide layer can be grown back by simply applying DC voltage, starting from lower voltage to slightly more than the nominal voltage. This process of forming must be done with current limited at very small values, and the voltage must increase slowly, over many hours up to a day or two. The forming stops when the leakage current becomes low enough (according to the datasheet specs of the given capacitors). Search for "procedure to reform old electrolytic capacitors", and you may find more details.Most probably the capacitors you found are 100% OK, butreformthem first. Do not suddenly apply voltage. They are most probably for 100/120Hz and high max current (e.g. for audio amplifiers) so they are not expected to have low ESR. Search their datasheet for the expected value.Other than that, 10000uF/100V and a known brand like Jamicon might be quite expensive as NOS electrolytic capacitors. Might worth selling them one by one on ebay, rather than wasting such capacitors in circuits that doesn't require high voltage.