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Surprising cable/buss test results

Skypower

Solar Wizard
Joined
Aug 23, 2021
Messages
1,861
I was watching Madi on Digital Mermaid assemble some flexible buss (jumpers), four #8AWG I believe and noticed how low the resistance readings were. This had me confused because I had bigger a cable and my reading were higher. Could tinned cable make the difference? YES!!!!!!

My test conditions: 54 volts at 100 amps.
Lugs: Newly purchased Selterm 2/0 1/4 stud
Cables: Ancor 2/0 tinned copper marine rated, fine strand.
Windy Nation 2/0 copper not tinned
Welding cable, fine strand.
All cable was 4-3/8 cut length (OAL)
Reference item: standard plated copper battery buss.
First 3” of cable was discarded. No oxidation noted on either cable.
Jacket stripped back no further than 3/4” so strands can’t bottom in lug and disorganize.
(Scraped) means outer wire strand surface was scraped with a utility knife while a twist tie held strands in place at end of strands. The lug was started and tie was removed.
Tinned cable was used as is, not scraped.
(Random) means strands were not straight and some were across others strands, disorderly, but 100% of the strands were crimped.
(Polished) means the inside bore of the lug had a few rotations of Scotch Bright to remove surface oxides.
Crimp: hydraulic- hex. Single crimp, single positioning. Hex impression reduce to die travel limit. Hex had crisp, complete non-rounded corners, no split line extrusion. Lug did not extrude in longitudinal dimension.
The cable was held into an arc shape with a wooden fixture while crimping to “lock in” the shape. A test piece (same length) was also done with a tighter bend using a buss it fixture it. The lugs were mount on the buss over/under to perfectly counter the twist when the lug was released.

……Ohms. ……Millivolts…… Watts
Buss……….. .07 … .004 …. .4

Ancor
(Polished)…… .07 ….. .004 …. .4

Windy …..… .11 …. .008 …. .8
(Polished/scraped)

Windy. …. .23…. .018 ….1.8(warm)

Windy. … .32 ….. .025. …. 2.5 (hot)
(Random)

My take away is a tinned 2/0 cable/prepped lug as a diagonal cell connect has the same resistance as a much shorter buss bar. Cell balancing should also be just as good an low heat buildup. Contact surface with the Lug on a small welded stud terminal should be superior to that of a solid buss due to the omission of a slot. The tinned-tinned connection may prove useful in many other locations.
There’s a possibility that a copper lug on copper wire may render an improvement but I don’t want the potential for corrosion so no test was done. Lastly, a battery internal resistance meter is an excellent predictor of cable quality.
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You, Sir, are a man after mt own heart and are asking the correct questions.

With the upmost respect, I will suggest your testing procedures need refined...
I am NOT laying into you, there is nothing more I like to see than a curious mind getting something done and NOT taking the manufacturers or retailer's propaganda as fact!

There is only ONE way to test load capacity, and that's loading the conductor, see if it heats up.

For instance, if a "200 Amp Conductor" actually is a 200 Amp Conductor, it shouldn't heat while conducting 200 Amps.

Simple, common sense proof: This is the purpose LOAD TESTERS where invented and exist. Think that one through for a minute... Think about exactly how many load testers you have seen in all these DIY Boobtube videos...

I have cheap 200 Amp loads to attach that most people overlook. I have Lithium batteries that can EASILY suck up 200 Amps for the load, and I'm not wasting that energy as heat, like with a resistor. All I need is a 300 Amp shunt/gage and less than half charged batteries...

If you want a regulator, use the charger function in your inverter. Those rarely exceed 200 Amps, but it will give you an idea and the losses are minimal, wiring is easy.

I'm so surprised that people completely overlook their own batteries... while working on said, same batteries. Like they can't see the forest for the trees. A working load right in front of them if they are building the SECOND battery, or third, or fourth... and so on...

I spent a LOT of money on panels to make those Amps, and a lot on batteries/cables, no sense making heat when I can simply charge yet another battery with a battery with minimal losses to test cables/conductors/termination.

You CAN test ohms (static) resistance under load, and that's eye opening to watch it shoot up as you reach conductor capacity, or even a reasonable portion of conductor capacity. Watch that static resistance (ohms per foot) shoot up.

It finds the cheap China copper alloy conductors/terminals real fast!

I used to "Trust But Verify", now I just assume everyone is lying until proven otherwise. Undersize copper, alloy copper, etc.
I get best results with U.S. made welding cable. You *Usually* get what you pay for with U.S. made name brands.

One of the biggest issues I see with wire/conductor sizing mistakes is using part time duty cycle scales, like automotive scales.

I use the old Brown & Sharpe scale. It's the 100+ year old industral scale that assumes 100% duty cycle. Since it's not changed in well over 100 years, it's pretty accurate. I rarely get heat at full capacity when using the Brown & Sharpe scale, I always overheated using the random automotive sizing scales.

If you can use it, welcome to it. If not, you didn't pay anything for it.
 
IF you are interested...

You have a few inches of cable end where you nipped it off. Strip that cable and waste a terminal crimping it on the cable...

Then sit back and look at the VOLUME of copper conductor,
Compair that to the VOLUME of the contact area thickenss where the battery attaches.

See any difference in VOLUME of conductor?

I know what the package said, but respectfully you are using terminals, not proper high amperage LUGS.

A proper high amperage lug will maintain VOLUME from wire contact socket all the way through the contact surface area.

Thin socket walls to be first that jumps to mind, proper heavy lugs will have thick walls to increase volume of conductor material.

Proper lugs will NOT have a 'Neck', area between socket and terminal area, AND WON'T BE HOLLOW!
Hollow means less conductor volume of material, with less volume than the conductor.

Then look at the contact area...
You have an impression of what looks to be the battery terminal in one picture.

That's your contact area, anything outside that circle DOES NOT COUNT since it can't make contact with the battery terminal and therefore can not conduct the current.

That contact area VOLUME must equal the wire conductor size from terminal to wire.

There is a reason everyone overheats 200 Amp rated cable at 200 Amps or under. Somehow these tubing terminals became the 'Standard', even getting called 'Lugs', but won't do the job an actual lug will do correctly.

Fact. The best conductor of electrical current is Silver.
Second best is copper.
Third best is gold.
(Fourth is aluminum, fifth is zinc, etc.)

Fact, ANY reduction in conductor VOLUME is restriction.

If you doubt this, let me put one of those terminals on a full load test, and we will see where it becomes a 'Fuse'.

That will ALWAYS be the 'Thin', least amount of copper volume spot on the terminal.

So, if you take basic electrical conductor physics at face value... (and PLEASE feel free to test this yourself!),

If you want to INCRESE conductivity AND protect your copper... Use Silver plating (also called 'Tinning', which is a generic term for the process), to increase the CONTACT PATCH AREA/VOLUME.

While the guys that watch too much Boobtube rant an rail against soldering, it can come in REALLY handy, just use the proper soldering materials...

Want to increase the contact patch area on your battery?

Silver bearing electrical solder solder (silver being MORE CONDUCTIVE than copper) a copper washer to the battery terminal.

Silver solder coat the copper washer for environmental protection AND to promote contact/conduction of electrical current.
Spread that current out so it can use the parts of your terminal end the bare battery terminal isn't reaching so it's wasted space/contact area...

Want to make your terminal to conductor have more contact area, promote electrical conduction between cable and terminal, silver solder it.

This DOES NOT replace the crimp, crimp THEN fill in non-conductive air gaps with silver solder. Replace non-conductive air gaps with highly conductive silver solder. This also protects your expensive, exposed copper. Added corrosion protection is a welcome secondary side effect.

Now, you will hear the "Aircraft/Vibration" argument from people that neither understand the benefits or application.

Commercial aircraft have wiring harness replaced on a schedule based on hours on the airframe. Exposed connections are sealed, and your battery cables will NOT being replaced on a schedule based on hours of service. Every protection you can afford them pays you in the long run, like using heat shrink tubing...

Secondly, solar batteries ARE NOT mounted in a high vibration environment unless you intend to use them on a jack hammer or rock crusher...

Third, your solar batteries will never fall out of the sky taking 300+ people with them...

Think the application through...

Dead soft copper washers with a metric hole are hard to come by sometimes. Again, application...

Since U.S. pennies 1982 and before are bronze, 95% copper, 5% zinc. With silver tinning/coating, more conductive than the air space you had before...

Drilling full hard bronze is a pain, but it works well in a pinch. I've been running some for 20+ years, fully load tested...

Silver bearing (silver content) electrical solder.

More from the tech geek archives...

Silver bearing electrical solder is 2% to 6% silver on average. Why does 2%-6% silver give so much better conduction?

Metalurgy/liquid flow of solderable materials. The silver will migrate to the OUTSIDE of a liquid solder ball.

If you look at silver soldered electrical joints that have weathered, you will see the distinctive blue cast of tarnished silver, not the white or gray corrosion of other solder components.

This happens inside the liquid solder ball also, the silver will be pushed up against the copper, to the 'Outside' of the liquid solder ball, even if it's a wire pushing into the solder ball. Everything gets first crack at silver content.

So silver solder punches WAY above it's weight class for the purpose of electrical conduction/conductor protection. There are meathead arguments, then there is science. Since you can see the silver tarnish on the exposed surface (distinctive color), try a test connection, cut it apart and let it tarnish in the weather to actually see for yourself. (I did because I didn't believe it even when it came directly from a heavy industral wiring textbook...)

Again, I encourage you to try it yourself...

Now, if it's a big, heavy electrical connection, mechanical connection FIRST, crimp, bolt, compression fitting, whatever... Then actual high heat silver in the joint.

While low temp electrical silver bearing content solder is good, full on high temp silver is better.
There is a reason all high amp generator connections are pure silver soldered... but that takes electro-magnetic induction or gas/oxygen torch to produce enough heat to flow pure silver.

If you doubt this, have a look at the Edison high Amp DC generators running the NYC subway system, in service for over 100 years... Or the Tesla/Westinghouse AC generators in service over 100 years.

Both high vibration/high amperage applications, both MUCH longer lived than any commercial aircraft wiring harness, some of the generators have been in service since before aircraft were invented and still doing fine...

Kind of kicks that 'Vibration' and 'Aircraft' arguments out the window without room for discussion when you think it through.

Again, just food for thought, if you can use it, welcome to it. If you can't, it didn't cost you anything...
 
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Silver solder does make a significant difference. While the majority of folks do not have the proper gear to make correct connections with high-content silver solder even the 7% variety will greatly improve connections properly soldered with it. I've used 7% for years when rebuilding and upgrading audio amplifiers.

 
I’m not ghosting you guys, I just didn’t see your comments yesterday and now I’m at work. It’ll take a while to digest everything said for an intelligent response .
Talk soon
 
I’m not ghosting you guys, I just didn’t see your comments yesterday and now I’m at work. It’ll take a while to digest everything said for

Silver solder does make a significant difference. While the majority of folks do not have the proper gear to make correct connections with high-content silver solder even the 7% variety will greatly improve connections properly soldered with it. I've used 7% for years when rebuilding and upgrading audio amplifiers.


I have a few batteries I don't know what the terminals are made of, but they won't accept solder, it simply won't stick.

That's rare for me, my experence had been silver solder sticks to everything conductive, including aluminum...

I don't want to overheat the terminals, so I gave up, but that's the only 'Miss' in a long string of 'Hits'.

I started electro-magnetic induction brazing and soldering, being dragged into the 21st century, when we had a job that required brazing (paste) around components that could get cooked. Now I'm crazy about it. Induction over flame if it's possible. This works quite well for adding surface area to the little battery terminals.

If it looks sketchy, I use conductive grease. Not everyone will want to risk a cell to see if it works without damaging the battery. Conductive grease is 100% guaranteed to work, zero heat, and depending on how liberal you are with it, it can protect the copper. The bolt/stud holds things in place like always.

if you think this through, its the MASS, since this is all copper, the mass of the conductor that does the job. The more mass and connective surface area you have, the more conduction you will get.

Seeing a picture of the old generator techs silver soldering a silver quarter to the frame of a generator clicked in my head.

The cast iron frames are underground there entire lives, the cast iron rusts, the quarter with a bolt hole drilled through it would be a never fail, high amperage electrical connection.

That spot is never going to scale or tunnel rust with the silver protecting it, and the silver spreads the electrical load out on the best conduction of electricity. The part cost them exactly 25 cents...

I've repaired the big old welders from WWII, every single one of them had silver soldered coil material, every high amperage terminal was silver soldered, and those battle ship welders can throw 600 Amps all day long, every day for 60-70 years...

Smaller connections, silver BEARING solder. The silver 'skin' that forms on the solder makes connection where no connection was before AND protects the copper conductor at the same time.

Since this isn't an aircraft, there isn't a need to inspect the joint for corrosion, thermal cycle overheat that opened the terminal crimp, etc.

I've wrote about it before, one of the first things I do on a trouble shooting call, during visual, I 'tug test' wire and connections. This is a tug, how hard depends on the size of the wire, but in about 50% of inspections I find wires coming out of crimp terminals or terminal screws that are loose.

Once a little barrel wire socket heats (thermal cycling) it has no way to clamp down on the wire again. A spot of solder keeps that from happening.

Most of those open barrels could use a spot of solder where the wire comes through them to seal up the copper, and that wire will never back out of that terminal again. Solder fills AIR SPACE, sticks the wire to the terminal, and makes a plug that can't pull through the barrel. There is no down side, no negatives here other than the time/materials it takes to do the solder.
 
That's exactly what

That's exactly what the infrared inspection looked like when the neighbor got a batch of that crappy China alloy wire...

When you push conductor up against it's amp capacity limit, that's what internal resistance per foot looks like also.

The bolts/device/battery is sucking heat out of the terminals, so they aren't quite as hot. The wire is insulated so it can't shed the heat and the problem compounds...

What happens when the bolts/device/battery gets enough heat it hits it's thermal limits? In batteries, it's usually the terminal seals or case seals around here...

The higher the temp, the higher the resistance... Self feeding resistance/thermal problems.
 
Dang Jeep you’re long winded, where do I begin?
As far as more testing, I’d have to break into my running system or dig out my Rube Goldberg M.O.T. High current top balancer from storage but life and present projects take precedence. You make many valid points. I use the smaller lugs (Ancor & Selterm) because of space constraints and limited gains performance/price over the “power lugs”. IMG_0656.jpeg
Yes the power lugs are far superior and you can get two crimps on them. I do use them when I can or when code requires it, but I never tried them on fine strand, only course aluminum or copper. Both Ancor & Selterm brand are UL marked but probably not for other than battery related issues. The smaller lugs have a close fit, any smaller and it would be difficult to insert the fine strand cable. My dies are modified to work specifically for those cable/lug sizes and combinations for maximum compression and least extrusion/minimization of the cross section. Could silver solder improve the conductivity? Probably, but only if it’s very high silver content, not just silver bearing. The higher the silver content the higher the temperature. Even if the heating event was minimalized the heat would damage a greater distance of insulation. The flux necessary is more corrosive and will capillary well up the strands. In order for any solder to flow there has to be a gap. For silver solder the gap should be no less than.003”. That means the solder won’t flow into the crimped area but only into the flare of the barrel. I don’t think it would be viable for most of us. My friend uses a cable welding system that I think will interest you. It takes place in less than two seconds and besides lugs it can also weld directly to steel. It’s very sparky!
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All copper from China is not bad. I ordered some from Amazon and was quite satisfied. I’m the 5 star review. I shaped and tinned it for a buss that directly connects to the bottom of my breaker. IMG_0657.pngIMG_0552.jpeg
 
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I'm ling winded? Look at your post! ?

You can't convey the details without more writing... so it gets long or it's a meme, not usable information.

Even silver bearing solder adds conductivity. It also KEEPS conductivity because it keeps the copper from corroding.

I like SPARKY! It means you are getting something done. Didn't say done correctly, but doing something.

Please, keep posting. I like seeing the process, someone thinking it through instead of repeating mistakes from boobtube videos.
 
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