Cheap eBay caps went bad  (on the shelf!) - Page 1
Forum section: electronics / general

author: mc349iii
author_rank: Contributor
timestamp: February 29, 2024, 05:04:17 pm
content: A while back I was fixing my electronic clock radio and it needed a capacitor replacing. I didn’t have any the right voltage / capacity but I managed to salvage one from an old board. The radio has stayed working since.So at the time I decided I should buy a few capacitors to have on hand for the future. So I bought a pack of 10 16V 1000uF low ESR caps from eBay for 99p (including postage!). They arrived and I put them in a tub on my storage shelves. This was Oct 2020.I came to actually use one yesterday and found that they had actually gone bad just sitting on the shelf. Two of them have popped their cans off and the rest are bulging and show signs of leakage.I’m surprised that they went bad just sitting on the shelf. They weren’t in direct sunlight and would have been kept at room temperature nothing above 30degC or below 10degC. Certainly well below their rating of 105 degC!Has anyone else had this happen?I’ve looked up a similar item on Digikey and a Rubicon or Nichicon equivalent is about 40p each plus VAT and shipping. So maybe they were suspiciously cheap! But hey they have gold writing on, so they can’t be all bad?Anyway maybe I’ll avoid suspiciously cheap JCCON caps on eBay in future.

author: bdunham7
author_rank: Super Contributor
timestamp: February 29, 2024, 05:10:10 pm
content: But are/were they truly "LOWESR"?

author: mc349iii
author_rank: Contributor
timestamp: February 29, 2024, 05:19:27 pm
content: I just put the least bulging example into my cheapo component tester.That's not too bad? Lost 400uF somewhere

author: bdunham7
author_rank: Super Contributor
timestamp: February 29, 2024, 05:23:57 pm
content: Apparently "LOWESR" is actually a bad phonetic spelling of "lousy".

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 29, 2024, 05:24:32 pm
content: They say "VENT" right on them, performed as advertised.Seriously though, some parts simply don't come cheap and electrolytic caps fall under that umbrella. You'll see it advised that beyond a small test/breadboard assortment you shouldn't bother stocking any, it doesn't make sense between the very wide variety and high cost, this is good advice. Buy as needed from trusted component suppliers, LCSC at the cheapest, personally I replace bad electrolytic caps with either long life Japanese brand parts from Mouser/Digikey or find something close enough that tests ok on a scrap board. Careful salvage is better odds than eBay caps, for that matter some of the larger cheap ebay caps are resleeved scrap parts pulled from ewaste.

author: themadhippy
author_rank: Super Contributor
timestamp: February 29, 2024, 05:40:06 pm
content: QuoteMaybe they were being honest about the quality ,but not very good typists and hit R instead of T.

author: Bud
author_rank: Super Contributor
timestamp: February 29, 2024, 06:22:17 pm
content: Hope you have learned the lesson.

author: floobydust
author_rank: Super Contributor
timestamp: February 29, 2024, 06:48:10 pm
content: Secret sauce in the electrolyte is the anti-corrosion additives, which why I would guess the caps outgassed... but in storage? It does seem quite strange and the paper looks dry.Or it's intentional- make a short-life component in order to sell again, sell more product.Many chinese cap manufacturers run a scam - they go on the stock exchange, pump up the brand and then dump then go belly up, accounting scandal etc. Or they are counterfeits. Massive shell game.For your time in labour, or in life, just pay extra and buy high quality parts, Nichicon, Chemi-con etc.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 29, 2024, 06:48:50 pm
content: It is perfectly possible that such capacitors can leak while in storage.As the name says, electrolytic capacitors have an electrolyte substance inside, which can be solid, liquid or gel. There is also a choice of materials such as Aluminium, Tantalum or Niobium.Liquid (wet) Aluminium is the choice for cheap capacitors, which have the liquid electrolyte being confined to an enclosure composed of aluminium and a rubber seal. If the electrolyte is not properly stabilized chemically (case of ultra cheap capacitors,), then it will react with the Aluminium or with itself, possibly creating gas and increasing the internal pressure on the enclosure. Give enough pressure and the rubber seal or the enclosure will give up and develop cracks, thus degrading the capacitor.

author: floobydust
author_rank: Super Contributor
timestamp: February 29, 2024, 06:57:02 pm
content: These babies made hydrogen or some other gas, enough to pop apart, while just sitting there, electricity not required. Quite impressive.I have even new, unused Panasonics that leaked a little at the leads/bung.I thought low ESR electrolyte is water-based, also has high leakage current.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 29, 2024, 09:11:34 pm
content: It is a similar root cause of batteries that leak with absolutely no prior warning... Internal chemical instability that creates gas, buildup pressure and consequently rip their seams.

author: thm_w
author_rank: Super Contributor
timestamp: February 29, 2024, 10:56:14 pm
content: Quote from: floobydust on February 29, 2024, 06:57:02 pmYeah, I also had name brand SMD caps leak and go bad just sitting on the reel. Think it was Panasonic as well. But this was after ~10 years not 4 years.

author: Whales
author_rank: Super Contributor
timestamp: March 01, 2024, 12:00:47 am
content: You see the datasheet specifies the shelf life as being lower than the service lifeI suddenly want to start my own dodgy alcap brand. Maybe I'll design an automated assembly line that uses kitchen aluminium foil, thin paper (transparent single-ply commercial toilet paper?), hot glue as the bung, steel fence wire as the leads andsodium bicarbonateas the electrolyte. Not sure what to make the can out of yet.Any ideas to make this more fun?