Copper pipe as bus-bar and ring-terminal connectors

spinningmagnets

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As many of you know, a local condemned house demolition can provide lots of free "Romex 12/3 cable", which is three strands of solid copper wire inside a sheath, 12-ga. Ten feet of Romex 12/3 will provide 30 feet of 12-ga wire. Being free is always nice.

I often see copper tubing being thrown away, and even if it is already stripped from a demo house, it can be bought at a recyclers for half the price of new copper tube.

Even if you are buying new copper tube at your local hardware store, it can be much cheaper than buying copper ring terminals (you can also slip a slightly smaller tube inside the larger tube to increase the ring-terminal copper mass).

Copper tube for water has a thin wall to save on costs, but copper tube of the same nominal OD for refrigeration systems has a thicker wall to withstand higher pressures, and also because a leak caused by a careless nick will be much more expensive for refrigerant, compared to a water drip. They both have the same outer diameter, so that they can both use the same end-connectors. I'm just posting this as a place to park dimensional info.

First, what is the width of a tube when flattened by a hammer or a vice? (of course, flat-bar thickness is double the tube-wall thickness, which varies)

__________________________________________Flat-Bar thickness

Tube stock OD___width if flattened_____________Type-L____Type-K

1/4"____.250"____9.0mm____.360"_____________0.060"_____0.070"

3/8"____.375"____13.6mm____.530"_____________0.070"____0.098"

1/2"____.500"____18.8mm____.740"_____________0.080"____0.098"

3/4"____.750_____

7/8"____.880"____33.5mm_____1.300"

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Calculating the copper cross-section, then convert to AWG-guage

1/4"-L____9.0mm X 1.5mm (0.060") = 13.5mm squared____6ga

1/4"-K____9.0mm X 1.8mm (0.070") = 16.2mm squared____5.5ga

3/8"-L____13.6mm X 1.8mm (0.070") = 24.5mm squared____3.5ga

3/8"-K____13.6mm X 2.5mm (0.098") = 34.0mm squared____2ga

1/2"-L____18.8mm X 2.0mm (0.080") = 37.6mm squared____1.5ga

1/2"-K____18.8mm X 2.5mm {0.098) = 47.0mm squared____0ga

https://www.engineeringtoolbox.com/awg-wire-gauge-d_731.html


"Type K has the thickest wall section of the three types of pressure rated tubing and is commonly used for deep underground burial, such as under sidewalks and streets, with a suitable corrosion protection coating or continuous polyethylene sleeve as required by the plumbing code. In the United States it usually has green colored printing.

Type L has a thinner pipe wall section, and is used in residential and commercial water supply and pressure applications. In the United States it usually has blue colored printing.

Type M has an even thinner pipe wall section and is used in residential and commercial low-pressure heating applications. In the United States, it usually has red colored printing" -Wikipedia
 

OffGridInTheCity

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spinningmagnets said:
As many of you know, a local condemned house demolition can provide lots of free "Romex 12/3 cable", which is three strands of solid copper wire inside a sheath, 12-ga. Ten feet of Romex 12/3 will provide 30 feet of 12-ga wire. Being free is always nice.

I often see copper tubing being thrown away, and even if it is already stripped from a demo house, it can be bought at a recyclers for half the price of new copper tube.

Even if you are buying new copper tube at your local hardware store, it can be much cheaper than buying copper ring terminals (you can also slip a slightly smaller tube inside the larger tube to increase the ring-terminal copper mass).

Copper tube for water has a thin wall to save on costs, but copper tube of the same nominal OD for refrigeration systems has a thicker wall to withstand higher pressures, and also because a leak caused by a careless nick will be much more expensive for refrigerant, compared to a water drip. They both have the same outer diameter, so that they can both use the same end-connectors. I'm just posting this as a place to park dimensional info.

First, what is the width of a tube when flattened by a hammer or a vice? (of course, flat-bar thickness is double the tube-wall thickness, which varies)

Tube stock OD___width when flattened

1/4"____.250"____9.0mm____.360"

3/8"____.375"____13.6mm____.530"

1/2"____.500"____18.8mm____.740"

Yes sir- I use flattened/drilled1/2 copper pipe to connect/parallelizemy base packs.

image_ihmjpb.jpg

In the beginning, I sawed off sections copper pipe, flattened 1/2 of it, and drilled a hole in other halfto make my own wire lugs for crimping... but i got lazy and started buying lugs as they aren't that expensive.:)
 

Headrc

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Excellent Spinningmagnets ...thank you for that synopsis of information. Yes refrigeration tubing is what I am currently using.
 

spinningmagnets

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Thanks for that link.

https://secondlifestorage.com/t-There-s-a-new-wall-in-Germany?pid=11550#pid11550

A while back someone asked why a lot of the featured builds had buses made from dual twisted 12ga solid wire, since pricing new wire seemed to be a bit expensive. It was pointed out that with some patience, most people can eventually scrounge up some free Romex. One strand of 12ga was "adequate" but does not seem to have much room for expansion, but if its free...dual strands is the type of overkill that is a good design because it lowers resistance.

Romex and copper pipe seem to be the most common types of free copper that I see on a regular basis (once you start looking for it)

Also, using near-free cells is not only financially good, many cells are discarded after they have lost only 20% of their capacity, so using a discarded cell that still has 80% of its ability to perform work is a good thing for everyone involved.

I'm also finding that a lot of industrial designs use aluminum as a conductor, but you should double the mass for the same current. Clean the surfaces before making any connection, and after verifying a good connection, seal it away from oxidation (dielectric grease, liquid tape, etc)
 

completelycharged

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Agree with pipe (any copper pipe) as a good option for making lugs by hammering a pipe flat with a cable in the end, add solder if uncertain.

Another tip for taking all the bends out of used wire is to stretch it rather than trying to run it through rollers as rollers work hardens the wire. The slow manual taking each bend out at a time is great for the first 30 minutes...

1.5x more aluminium area as an easier approximation (1.5371...) , rather than mass as copper is a lot more heavier. This only works as long as your maximum conductor current and shape does not result in higher surface currents, which then need the conductor to be more oversized or flatter, like hammered pipe......
 

Redpacket

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I would not be keen to use aluminium for two main reasons:
- impractical to solder to
- tends to oxidize leading to bad joints
Great for heatsinks, not so much for electricals: my two cents anyway :)
 

completelycharged

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Oxidisation : oxide layer is 1-2nm (nano meter 0 few atoms) thick and good joint pressure (bolting) is good enough for contacts upto a few hundred amps without heating.. and without 'cleaning'... this is always a slight misconception with aluminium.

Solder : I would say never solder to a busbar.. copper or aluminium.... bolt. you can theoretically solder to aluminium but never done, so would agree it is impractical to solder to.

Aluminium only makes sense for a busbar because aluminium in wire form it is far too liable to embritle and break with very little bending.

Agree on heatsinks, good block of alloy is great :
Even used some large lumps of aluminium on top of the wood burner to heat them up and then take them to another room as 'room heaters'.... few kg of aluminium at 200C makes for a 1-2kWh heater. Albeit a slight issue and risk walking round with large lumps of metal liable to set the house on fire if you drop them on the floor, lol. 'bit of an experiment' might be a suitable term. lol. not quite a heatsink..
 

Sean

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completelycharged said:
Aluminium only makes sense for a busbar because aluminium in wire form it is far too liable to embritle and break with very little bending.

A fair amount of the UKs overhead distribution network is strung together using ali conductors, ditto for HV trackside ....
 

100kwh-hunter

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My experience with soldering on aluminium that it is not impossible, but very difficult.
You can weld it.

@Sean, in Holland we have the same in the ground, since 10-15 years ago they only use aluminium.
I don't know if they do it with alu in the hv 50kv and up also. Most of them are above the ground
 

completelycharged

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For DIY builds aluminium only makes sense for a busboar. yawn.
 

100kwh-hunter

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In general what is better?
Is it better to coat the ring terminal with tin and put your wires in and squeeze it tight, or fill it all the way when you squeezed the wires in?

I agree on aluminium for busbars, its cheaper than copper tube.
You must drill anyway for your bold.


Thanks.
 

OffGridInTheCity

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Purchased lug vs a couple of my earlyhome made ones from copper pipe. Must have had a couple of beers for that one with drill hole off a bit :)

image_jfqxjf.jpg


The purchased one is so much prettier for only 80c each.
 

Korishan

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And if you want to go chinesium route, you could get them even cheaper. You can't exactly fake copper, unless the tin plated ones are actually aluminum instead. Easy fix, don't get the tin coated ones.
But even if they are tinned coated aluminum, the size of the lugs are usually large enough to handle any electrical discrepancies.
 

DomingoRP

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Hmmm. I may not be an 'Electrical Engineer', but I'm assuming that using wire is more effective due to the strands because the electrons have multiple paths on each strand to move. This is just a theory/thought.
 

daromer

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Many thicker Wire here is alu actually. My old 35mm2 that was to My garage was aluminium :) got 50m 4g35 IF anyone want it
 

completelycharged

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Hand wound terminals are sometimes better than lugs depending on the bolts and they are cheap (few extra mm of wire stripped off the end)


image_npowud.jpg

These are some bad examples of mine...

Some crimp terminals are way undersized (wall thickness) for the conductor sizes so this is where a DIY wire loop can also distribute the current better and a larger mass (surface area) for heat dissipation.


Redpacket, I like those earthbars.. the 300A 36 hole option.. When I used to use terminals like that I would put the wire so that both screws are applied to a single cable and then tighten the closest screw up to a lower pressure than the furthest. The reason is the furthest is full on, so absolute pressure and lowest surface contact resistance, but not necessarily the lowest resistance terminal due to chage of shape through wire compression. The second terminal is to apply some (90%) pressure buit not to distort the cable conductor as much. Tight terminal is 10% short of the screw shearing off.

The top cable example above is an extra outer binding layer, which makes the cable less likely to be split or cut by screw pressure when tightening and fills the void better as well....

Back in the 1990's you never saw aluminium SWA. The only place aluminium was used was on the likes of 132/400kV overhead lines with a steel wire core and outer alloy wrapper. 33kV and lower lines were all solid drawn single strand copper. Aluminium as a conductor for larger cables can now be cheaper and a lighter cable to move around.... try routing a 200m long 3 phase 300m2 copper SWA cable with a few people and no machinery (other than a manual cable winch) and you get the idea.

The main downside and limitation with aluminium for small cables is embrittlement with bending.


In relation to stranded wire - it has to be insulated for the concept to work if it is for current handling reasons :
https://en.wikipedia.org/wiki/Litz_wire
The article says RF, high frequency, however it applies to high current conductors as well. This is part of the reason when you have 200+ amp cables you start to need more and more mm2 per amp for a cable.
 

100kwh-hunter

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image_rtqptb.jpg


image_lkiqyv.jpg


Well..I am not so pleased with the end result.
Aldo i can make them pretty fast.

image_fltygw.jpg


image_ewofuy.jpg


image_drctwm.jpg


image_byiusr.jpg


image_gpjiwt.jpg


Boil the oxidation layer of with vinegar salt and water.


image_ynqdzh.jpg



completelycharged, i like that idea very much, its very simple and effective.
But the purchased one of OffGridInTheCity is also very appealing.

Korishan, that chinesium route, you mean this one? cous i planning to buy one of those:
https://www.aliexpress.com/item/329...4.0&pvid=b166b803-d9b5-4f88-b03b-b4030138d169.

or

https://www.aliexpress.com/item/32902334044.html

And probably i will share it with some pw builders here in "noord-holland" the Netherlands

Thanks in advance
 

owitte

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:Redpacket said:
The user "Owitte" is using tubing - he's flattened just the ends, then drills & bolts together:
https://secondlifestorage.com/t-There-s-a-new-wall-in-Germany?highlight=owitte

thanks for linking to my project thread :D . I decided to go with copper pipes because of mainly four reasons:

  • the price: Even if you can't get used pipes from somewhere, it's available for a reasonable price at any hardware store
  • electrical properties: Copper is a good conductor with minimal resistance
  • physical properties: It's easy to work with, you can bend and solder it easily
  • and last: it's quite solid and strong enough to hold the weight of the battery packs on my wall, so I don't need extra holders
I also made all of my terminals from copper tube by cutting it in small pieces (40mm), than flattening half of it, drill a hole in the flattened part and solder the cables into the hole on the other side. I also tinned the flattened part to prevent corrosion.

But you also have to be careful concerning the electrical contact over a long time. I noticed that most of my packs become loose after a while, maybe because the copper is also a little weak. My solution was using steel spring washers, since then I didn't have any problems anymore.

Have sun :cool: !
Oliver
 
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