Low resistance 4 mm patch cords  - Page 1
Forum section: electronics / testgear

author: JohnPi
author_rank: Regular Contributor
timestamp: October 31, 2021, 11:58:23 pm
content: I am working on some low voltage, medium current circuits (5 V, 20 A), and the standard Pomona 4 mm patch cords (which are extremely convenient) have too much resistance to allows my circuits to operate well. I am building some alternative cords using 10 awg silicone cables which are great (about 3 mΩ instead of 20 mΩ), but I don't have a good 4 mm plug for them -- one that handles the wire thickness and also makes a neat and strong connection.Any suggestions ? Are stackable plugs available ?

author: BradC
author_rank: Super Contributor
timestamp: November 01, 2021, 12:32:14 am
content: I made some with 8mm2 (8AWG) recently. I used piggyback plugs and soldered the cable into the socket."Not ideal", inflexible, ugly and hacky. Having said that, it did the job.I've used these :https://www.altronics.com.au/p/p9281-red-stack-type-banana-plug/with 12AWG cable. Not ideal, but it just fits with a bit of gentle persuasion.Edit : A 30 second digikey search :https://www.digikey.com.au/en/products/detail/mueller-electric-co/BU-3110410-4/7917533

author: BrokenYugo
author_rank: Super Contributor
timestamp: November 01, 2021, 01:01:02 am
content: At this current ad wire size perhaps switch to spade connectors and binding posts?

author: Someone
author_rank: Super Contributor
timestamp: November 01, 2021, 03:33:37 am
content: https://www.eevblog.com/forum/testgear/banana-plug-and-big-wires/Thick cable + stackable, no.

author: Hydron
author_rank: Super Contributor
timestamp: November 01, 2021, 08:26:10 am
content: I think RS does some 32A rated ones with piggyback plugs

author: Someone
author_rank: Super Contributor
timestamp: November 01, 2021, 01:02:18 pm
content: Quote from: Hydron on November 01, 2021, 08:26:10 amRating (non-continuous?) of plug/socket only, not the cabling. The space they leave for cable is too small to practically carry those currents.

author: nctnico
author_rank: Super Contributor
timestamp: November 01, 2021, 01:41:29 pm
content: Quote from: JohnPi on October 31, 2021, 11:58:23 pmHirschmann has 32A leads with banana plugs. When I need to get more current from A to B I usually use 2 or more leads (with stackable plugs) in parallel but 4mm banana plugs top out at around 30A if you use good quality ones.

author: Hydron
author_rank: Super Contributor
timestamp: November 01, 2021, 02:28:27 pm
content: The Hirschmann ones (what I was thinking about with my earlier comment about RS) are 2.5mm^2 (i.e. they might get a little warm, but will do 32A fine in free air), while there are also some (pricey) Mueller 10 AWG ones which are rated at 45A (35A @ 180C!!), e.g.:https://uk.rs-online.com/web/p/test-leads/1801286

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 01, 2021, 07:51:42 pm
content: 2.5mm²/32A also available from Staeubli (formerly MC).They also supply test lead wire (ultra-flexible, PVC and Silicone) with up to 6mm² in their standard line and up to 95mm² under the 'Silistrom' label.

author: wizard69
author_rank: Super Contributor
timestamp: November 02, 2021, 02:39:22 am
content: Quote from: BrokenYugo on November 01, 2021, 01:01:02 amThis would be my first thought, but would go one step further and suggest ring terminals on at least 1/4" studs.Other approaches would be with connectors specifically designed for such loads. The battery connector designed for RC toys might be one approach. Or you might try Anderson Powerpole connectors:https://www.andersonpower.com/us/en/resources/PowerPoleResourcesPage.html.In fact I'd suggest looking into Powerpole first as you can find a lot of stuff built around the systems to support a power supply build.

author: 1audio
author_rank: Frequent Contributor
timestamp: November 02, 2021, 05:22:53 am
content: You probably want these: Superior Electric banana connectorhttps://www.newark.com/superior-electric/pp250gwt/test-plug-pin-plug-250a-white/dp/98F3252The data sheet has "banana like" connectors up to 250A. The ones compatible with a 4mm banana connector are rated to 25A. These are solid brass and quite substantial. They have matching female connectors and double banana sockets.

author: JohnPi
author_rank: Regular Contributor
timestamp: November 17, 2021, 01:57:58 am
content: I ended up making my own. I took the metal core from (removed the plastic) some older or broken Pomona 4mm patch cords; I 3D-printed a replacement cover, but now with a wire entry diameter to fit the 10 AWG stranded silicone wire I have. By bending the stripped wire end 90 °, and tinning, I could solder it to the metal core, then press fit the 3D cover. It looks neat and clean; the resistance is about 1/10 the original wires, and I have the 'good' 4mm banana plug." alt="" class="bbc_img" />

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 17, 2021, 04:09:57 pm
content: In the context of heavier currents (say, 20A to 32A) I came across several cases where wire or plug resistance could not be neglected (or even resulted in notable temperature rise).Now using a 10mm2 cable (approx. 8AWG) with some banana plugs sold for loudspeaker purposes. Works very well. The cable is super flexible which is nice, although I might look more into different conductor materials in the future.

author: electr_peter
author_rank: Unknown
timestamp: November 17, 2021, 04:38:27 pm
content: Quote from: RBBVNL9 on November 17, 2021, 04:09:57 pmInteresting, did you add ferule to a cable (blue round part)?I am looking at making 8-10mm2 cables for up to 40-60A currents, probably with RC style XT90 connectors.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 17, 2021, 04:48:30 pm
content: QuoteYes, that's a ferrule to ensure good contact and prevent damaging the strains of the wire.In the comings days, I'll try to measure the resistance of this solution.QuoteUsing XT60 plugs for a number of (not so high current) applications and that works very well.

author: electr_peter
author_rank: Unknown
timestamp: November 17, 2021, 05:57:39 pm
content: I will have to check XT60 vs XT90. I think just the male metal part (without plastic) of XT90 ideally fits bigger sockets of power supply.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 17, 2021, 06:06:48 pm
content: I never disassembled an XT90 plug to use the pins otherwise. But some websites seem to report the pin diameter is 4.5mm. Also, they might be fairly short. So I have doubts whether this is a good replacement for a banana plug… (but perhaps some sockets have tolerance?). An experiment would tell…

author: electr_peter
author_rank: Unknown
timestamp: November 17, 2021, 06:42:10 pm
content: XT90 plug is for power supply sockets where regular standard 4mm jack is too loose. Mostly on higher current PSUs (from 20-30A and up). Either XT90 as a banana or spade crimp connector.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 17, 2021, 07:55:47 pm
content: QuoteI see, interesting. Out of curiosity, do you mean these PSU aredesignedto take an XT90 size pin and can you perhaps give an example)? Or do you mean that some PSUs simply have too loose a connection when used with a regular 4mm banana plug?The higher current PSUs I found most often have screw terminals (for instance, BK Precision 9150), screw clamp connection (e.g. on Elektro Automatik EA PSI 9200-15), or M6 or M8 bolts on a metal rail or on a brass plate (various versions of EA PSI 9000 series). Some have safety connectors that take wires or spades but also 6mm plugs (such as AimTTi QPX series).

author: electr_peter
author_rank: Unknown
timestamp: November 17, 2021, 09:05:30 pm
content: Quote from: RBBVNL9 on November 17, 2021, 07:55:47 pmI mean PSUs with loose (wide internal diameter) banana screw terminals. These just happen to work (but not designed) well with XT90 internal part as substitution for banana connector. For example, Gophert CPS3220, see videohttps://youtu.be/hX5xtOvAE4I?t=540I am not certain what higher diameter socket is supposed to accept at >20A currents

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 17, 2021, 09:13:15 pm
content: QuoteThanks for the reply. I have not come across this problem yet with my own PSUs, but will keep it in mind if I ever encounter it.PS. Working with my son on drone motors, I came across the fact that these folks use 3.5mm jacks (!). Had to buy a bunch of them. There are too many standards ;-)

author: macboy
author_rank: Super Contributor
timestamp: November 18, 2021, 08:21:32 pm
content: Search amazon for "4mm cross bullet connector". e.g.:https://www.amazon.com/dp/B07ZT58XNN/These are heavy connectors that can take abundant current. They come as male/female sets so you could cobble together a stackable plug if that's what you want. They require a closer tolerance socket than the normal spring type banana plugs, so they might not fit tightly into absolutely every banana jack on your bench.

author: TimFox
author_rank: Super Contributor
timestamp: November 18, 2021, 08:54:46 pm
content: Not compatible with standard banana plugs, and quite expensive:https://www.specialtyproducttechnologies.com/superiorelectric/products/electrical-connectors/supercon-electrical-connectorsandhttps://info.specialtyproducttechnologies.com/5-way-supercon-catalog-downloadI found them very useful at high current levels, even at frequencies around 10 MHz.

author: BrokenYugo
author_rank: Super Contributor
timestamp: November 18, 2021, 09:55:23 pm
content: Quote from: macboy on November 18, 2021, 08:21:32 pmThank you for providing that search term, I was struggling the other day to find what the good one piece split pin type are called. Seems "cross" and/or "high current" are the key terms.

author: JohnPi
author_rank: Regular Contributor
timestamp: November 20, 2021, 08:41:20 pm
content: Here's the final result and the source files are attached.Pomona 4mm cover.zip(638.29 kB - downloaded 52 times.)

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 20, 2021, 11:59:36 pm
content: These are Pomona 5000 Volt 36 in banana patch cords,do you think they would be low enough resistance?https://fairradio.com/product/rj-5031-3y/

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 21, 2021, 12:06:16 pm
content: With such a high voltage rating, most of the diameter is going to be insulation. So the actual copper will be rather less then with standard test leads.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 21, 2021, 12:15:47 pm
content: If you look for high voltage or high current test leads connectors in good quality, take a look at the Swiss company:Stäubli / MC / Multicontacthttps://www.staubli.com/en/connectors/electrical-connectors/In my experience they are one of the best.

author: mariush
author_rank: Super Contributor
timestamp: November 21, 2021, 12:23:56 pm
content: Maybe there is room to use the standard molex mini-fit connectors used by video cards?Being mass produced headers, you can buy them cheap, and you can also buy the connectors cheap, same for crimping tools.For example use a pci-e 6 or 8 pin connector, either right angle or straight up ... you have 3 awg18/awg16 pairs of wires for low voltage drop and contact resistance, and you can get mass produced 6/8 pin pci-e extensions cables or make your own.example:https://www.digikey.com/en/products/detail/molex/0455580003/3311349Could have two side by side and thick traces connecting each row for "pass through" ... first is input, second is output ... or the other way around ...