Two Caps. same value. same ratings, same brand. different size. Why? - Page 1
Forum section: electronics / beginners

author: Pedram
author_rank: Regular Contributor
timestamp: August 22, 2014, 06:03:36 pm
content: Hi, i have two caps with same value, same ratings, same brand but they are different size. Why?ESR?Images :

author: SeanB
author_rank: Super Contributor
timestamp: August 22, 2014, 06:08:32 pm
content: Could be ESR or different ripple current ratings. The larger one will likely have a higher current rating ( though with 1uF 50V it is hard to think that you can actually exceed the current rating before it becomes an inductor) and likely a lower ESR. It could also be that they are made by different OEM suppliers and are branded for this particular manufacturer, or one is a "second source" ( AKA fakalytic) part.

author: Precipice
author_rank: Frequent Contributor
timestamp: August 22, 2014, 06:10:14 pm
content: Possibly a good engineering reason, more likely because the bigger size used to be the 'right' size, and there are a million purchasing people buying for new runs of old products.Heck, you can still get 1210 100nF capacitors - same deal. Reworking a design just because time has moved on is a lot more expensive than just buying suboptimal parts, a lot of the time.If you really care, measure (and hope they'll be the same next time) or fetch the datasheets.

author: Pedram
author_rank: Regular Contributor
timestamp: August 23, 2014, 11:57:25 am
content: why there is no marking about ESR or ripple current rating ? BTW do we have genuine cap brand FUJI? i just found a japanese Fujicon but their logo is different.

author: DanielS
author_rank: Frequent Contributor
timestamp: August 23, 2014, 01:09:30 pm
content: Quote from: Pedram on August 23, 2014, 11:57:25 amLow-ESR and other specs like that are rarely marked on the capacitors themselves. You usually need to find the brand, model name and look up its spec sheets for the value and dimensions you are looking at.For example, Panasonic's FM-series capacitors have a few values that are available in two different physical formats and the taller ones usually have lower ESR / higher ripple than the wider ones.

author: wraper
author_rank: Unknown
timestamp: August 23, 2014, 01:24:57 pm
content: Quote from: Pedram on August 23, 2014, 11:57:25 amThey are never written on capacitor, only in datasheet. These caps likely are Chinese crap, so series are not mentioned on them too. Small sizes exist to put them where larger ones do not fit. Usually sizes are different for different series, however within the same series various sizes also exist. Smaller capacitors usually have lower endurance and ripple current rating.You can call them genuine Fuji - no one knows Chinese brand. Those are not Fujicon which is also Chinese BTW, where did you get any mention of Japan?

author: Pedram
author_rank: Regular Contributor
timestamp: August 23, 2014, 03:29:46 pm
content: Quote from: wraper on August 23, 2014, 01:24:57 pmjust a guess. fuji mountain is in japan etc etc ... lol .

author: K1JOS
author_rank: Regular Contributor
timestamp: August 27, 2014, 01:04:02 am
content: I was struggling with this same question recently as I tried to find computer grade, screw terminal, power supply electrolytics for my ham radio HF amplifier. Its a tight fit in the amplifier and I need 7 of these to squeeze into a confined space with no wiggle room.The original part is a 350uF 450V (-20-+50%; 85C) Cornell Dubilier (CDE) and is almost impossible to get and sells for $35-50 each with a large minimum order. Other manufacturer's lytics with similar specs are much commonly available but all are either too large diameter and/or too long. On a hunch, I searched in the same Cornell Dubilier CDE series and saw a 380uf 450v with identical specs for ESR and ripple and it was almost 2" shorter and half-the price !! On the CDE spec sheet these are indistinguishable and clearly within each other's tolerances.So why the major difference in size and cost?? Someone at CDE must know why :-)

author: SeanB
author_rank: Super Contributor
timestamp: August 27, 2014, 07:18:46 pm
content: Probably the difference is in either lifetime or derating for either high frequency use or for extended temperature operation.