Help with part sourcing a capacitor

Hello,

I am looking for a capacitor with around 3000uf capacitance and maximum 3 mOhm (three milli Ohm) of ESR... the low ESR is very important. I am looking for one with the smallest package size as possible.

Any ideas?

What voltage? And 3mOhm at what frequency?

You're probably looking at a conductive organic polymer based tantalum or aluminum.

Sorry for the lack of info...

its for automotive use and operating at 12V. So the voltage rating on the cap should be above 15V...

Thanks

ESR is frequency dependent, so what frequency?

You're looking at a 16V-25V Aluminum Polymer. Which is going to be very difficult to get such low ESR at that voltage. However, you aren't going to get a single cap with 3000uF either. So you'll be putting something like 3 of these in parallel: http://www.mouser.com/ProductDetail/Panasonic-Electronic-Components/16SVPF1000M/?qs=OE1iw1LrrPFPku2E0PqL4w==

Note that these are not traditional electrolytic capacitors with a wet electrolyte. These have a conductive polymer as the electrolyte that is solid (and doesn't wear out).

Might these super caps. work? 2200uf at 16V http://www.ebay.com/itm/DR03-50pcs-Super-capacitor-2200uF-16v-for-wagon-lighting-NEW-/350840726690?pt=Model_RR_Trains&hash=item51afbca4a2

jackwp: Might these super caps. work? 2200uf at 16V http://www.ebay.com/itm/DR03-50pcs-Super-capacitor-2200uF-16v-for-wagon-lighting-NEW-/350840726690?pt=Model_RR_Trains&hash=item51afbca4a2

Those are not supercapacitors.

Supercapacitors are really EDLC (electrical-double layer) construction. Those capacitors are traditional Aluminum Electrolytics with a wet electrolyte. Other than the voltage/capacitance value, the other dead giveaway it isn't a EDLC is that the temperature rating is 105°C. In fact, it is probably this part number: http://www.mouser.com/ProductDetail/Nichicon/UVZ1C222MHD/?qs=sGAEpiMZZMukHu%252bjC5l7YfeziKtNZn%252bTMB%2ftYYRIvzM%3d

The ESR of those caps will be very high, [u]much higher[/u] than then requested 3mOhm.

Here's a list of in-stock 3mOhm 4700uF AL electrolytics at Digikey. Pick your size http://www.digikey.com/scripts/dksearch/dksus.dll?pv724=595&FV=fff40002%2Cfff80009&k=capacitor&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25 If packages are too big, search for other types and similar filtering.

The frequency is dependent on the capacitor I find... In the end I want to have the smallest ESR as possible and I will tune my frequency accordingly... The desirable frequency is in the range of 1 to 4 kHz...

Thanks

James,
I expect you have much more knowledge about capacitors than I, but can you explain to me how you determined that the capacitors I presented labled “2200 mf 16Volt super capacitors” were not super capacitors, and you think they are really 2200mf 25Volt. Mouser says it is 16Volt on part of the specs, but the photo shows 25Volt. It’s ok, everyone makes mistakes occasionally. Mouser is not perfect.

Ha James, help me out here. Am I missing something, or is Mouser’s specs not reliable. Looked at another cap
http://www.mouser.com/Search/ProductDetail.aspx?qs=o4eR8uSks2c6R%2FZg1GtAWQ%3D%3D
on the same screen it shows 3 different mf (look at the image), and two text spots. It gives 27F, 27mf, and 820mf. Am I missing something, or is their specs worthless?

Thanks, Jack

FardinB: The frequency is dependent on the capacitor I find...

DA is about the same from 1-4KHz for most dielectrics, so you can consider it the same frequency. Keep in mind that different dielectrics rate the ESR at different frequencies. Polymer-Ta and Polymer-Al use 100KHz, the ESR is on the order of a magnitude lower than 1KHz.

jackwp: I expect you have much more knowledge about capacitors than

I work for a capacitor company.

jackwp: but can you explain to me how you determined that the capacitors I presented labled "2200 mf 16Volt super capacitors" were not super capacitors

As I said, "supercapacitors" are a specific type of capacitor. Sometimes the term gets misused like in the eBay listing. The seller is calling them "SUPER Capacitors" (I added the capitalization) which is not really a "supercapacitor." As I said, a true supercapacitor is really considered a EDLC, which defines its construction. 2200uF at 16V is extremely low for a real supercapacitor.

As I said, the real point to notice is the 105°C temperature rating. "Supercapacitors" or ELDC can't operate at that temperature. Certainly not one that would sell for 10s of cents. So that's easily the biggest red flag.

jackwp: Mouser says it is 16Volt on part of the specs, but the photo shows 25Volt.

That's the reason Mouser states: "Images are for reference only See Product Specifications" under every picture.

jackwp: Am I missing something, or is Mouser's specs not reliable. Looked at another cap

In that case, the specification is wrong. Ignore the image, those are for reference only. The specification should read "27F" not "27uF". See the button that says "See an Error?". Guess what that does.

jackwp: Am I missing something, or is their specs worthless?

That's rather extreme given how many parts they have, the fact they link to the actual datasheet, and will fix errors reported to them within 24 hours.

James, I concede to your better knowledge of capacitors, and appreciate you helping me understand. No competition intended, I just wanted to learn more. Have you been able to find a capacitor that fills the bill for this thread? May not be one, I don't know.

Thanks, Jack

jackwp: No competition intended, I just wanted to learn more.

I didn't know there was one. I was just trying to answer succinctly. I give 2 day seminars on nothing but the technical aspects of capacitors. It's tough to boil it down into a few internet posts.

I'm having a hard time convincing fellow members of a maker group I'm in that there is more to know about capacitors than voltage and capacitance to get them to sit still for a 90 minute lecture.

I'd love to sit through a 2 day seminar on the subject! No sarcasm.