Electrolytic capacitor tolerance to cold temperatures? - Page 1
Forum section: electronics / beginners

author: highvoltageboogie
author_rank: Contributor
timestamp: July 19, 2025, 11:26:17 am
content: How cold one can freeze electrolytic caps before they get damaged?Well known brands seem to have ratings varying from -20 to -55 deg C, and these are operating temperatures. Storage temperatures might be even lower? But if we take random Chinese caps used in product X, what would be a good guideline?Background - I bought a set of speakers from a home that I suspect may have bed bugs. I wrapped the speakers in plastic and put them into freezer, adjusted it to as low as it can go, about -25 deg C.I assume that caps, or other components, should not be damaged by such temperatures. Or would they?

author: jwet
author_rank: Frequent Contributor
timestamp: July 19, 2025, 02:40:09 pm
content: This is probably safe for storage- keep the duration to the minimum required to kill the bugs. Somewhere around -45C is a magic number for a lot of polymers and plastics, don't go that far. There will be a lot of contraction due to thermal "expansion". This can stress and sometimes break seals. The other danger is crystallization where the structure of the electrolyte changes. After the cold soak, bring it out and let it come to room slowly. Consider wrapping it in insulation to slow warming. A towel or blanket would suffice. Temp shocks are really hard on things.Remember that most things shrink when frozen. We're used to things with water in them which is one of the only things that expands when frozen and we have this image of bulging, frozen pipes which is unique to water containing stuff.I did a lot of military design early in my career. We had a great big Thermotron and a Ling shaker table. We had to run all our equipment through a 10 cycle 2 day run of of -62C to +62C in the oven and then a 10 minute 6G random haystack shake on the Ling. It was called Workmanship Screening- I was a youngish engineer that supported final test among other duties. I learned a lot during that time. I grew to truly hate adhesives in manufacturing and learned to love red loctite. This whole workmanship screening is the exact abuse that equipment gets when strapped down as open cargo on a C-130, the extreme temps and the vibration for a 30 hour flight might be the worst treatment an instrument ever gets.

author: mawyatt
author_rank: Super Contributor
timestamp: July 19, 2025, 03:11:48 pm
content: Remember those shake tables, ours were driven by Macintosh Tube Amps. They usually were run at night so not to bother everyone (you could hear them all over the campus), but occasionally during the day. Also had the temp chambers, EMI, explosive decompression chamber, and even a Flash X-Ray in a lead lined special room. All the requisite Mil-Standard testing capability in-house, and tried to stay way from all this unless our equipment was under test.Best

author: jwet
author_rank: Frequent Contributor
timestamp: July 19, 2025, 03:43:09 pm
content: Our equipment was dishwasher sized (Radiation Monitor for Nuc Navy- IM-239). The oven could take three units at a time- like Japanese hotel room. The Ling could shake a half ton load! We also used it for resonance sweeps during first article where we would find and dwell at all the resonances for 1 hour each. A great way to ruin things.

author: highvoltageboogie
author_rank: Contributor
timestamp: July 19, 2025, 06:53:16 pm
content: Quote from: jwet on July 19, 2025, 02:40:09 pmThanks. I already took them out after keeping them there for about a week. Wrapping them in blankets would have been a good idea, I just took them directly to room temperature. The amount of moisture that condensed on them was crazy in this weather, I think I will let them dry for several days before use.

author: jwet
author_rank: Frequent Contributor
timestamp: July 19, 2025, 10:17:05 pm
content: The big Q- does it work, let us know. If not, I can't think of anything besides electrolytics that would have a hard time with those temps. Flash rust in the tight tolerance of the speakers might be an issue with the condensation but it might just work itself out. Don't crank it full blast first thing.

author: Zero999
author_rank: Super Contributor
timestamp: July 20, 2025, 08:39:24 am
content: Electrolytic capacitors contain water which expands when frozen, as other materials contract, so there is a risk of it bursting if frozen, but the electrolyte has other chemicals and anti-freeze, which should be fine down to -25°C