Heavy DC Inverter Cable Making

Hi,

I dont have the 4 gauge crimping tool anymore nor the 250 watt soldering iron, yet i will probably want to make some heavy duty cables for the input side of a 12vdc to 120vac inverter, the kind you connect to your car battery via heavy alligator clips and one end just stripped or possibly with a nice heavy duty round circle lug.

Here's the thing...
Since i dont have the heavy duty crimp tool anymore nor a really big soldering gun (i have 100watter that's it) i am looking for other ways to construct heavy duty cables like this where each end might need a crimp connection, or alternately some other idea.

So anyone out there ever have to do this, maybe with a hammer or a vise grip or something else to crimp with, and how do those big (gigantic) alligator clips connect to the heavy 4 gauge wire?
Come to think of it i dont think i ever had to crimp or otherwise connect a huge alligator clip to a wire only the smaller ones for testing smaller electronic equipment.

Any ideas, comments, or suggestions? Keep in mind this will be for wires that are 6 gauge or 4 gauge, nothing lighter than that.

hi Al,
Is your kitchen stove gas or electric.?

You can place the battery lugs on the stove ring to heat them to around 350C, then use a solder stick and plumbers paste or spirit.

E.

Hi Eric,

You think a flame would work then? How about a propane torch? They used to make those huge soldering iron tips for those torches but im not sure if they do anymore or not, and it's been so long since i've used one i dont remember how well they work.

Have you ever used a flame to solder with?

hi Al,
You can buy a butane gas soldering iron, so yes I have used a gas flame, also you could get a small hand held gas torch that would heat the lugs to 350C.

If you use flux less solder sticks you need a flux paste or spirit.

E.

Try an Industrial supply store that sells plating equipment. I used to work at a plating shop and we could from a local store get crimp connectors for up to 00 cable that went on with nothing more than a hammer, we used them all the time. If you want real low loss, solder after you crimp, you could use general plumbing solder/flux as long as you clean the flux off real good afterwards.

Alec:
You only supplied half the puzzle. #4 wire and ____ stud size are both needed.

At an electrical supply house, you should be able to find ring lugs that use compression from a screw. I've used smaller ones to ones for 200 A welding cables. The later used a HEX key.

e.g. see PDF page 39+ https://www.electro-tech-online.com/custompdfs/2012/05/ShearBolts.pdf

These are not exactly what I was thinking of.

You might also want to visit a local marine store. They might be able to do the compressions for you.

Here is an interesting resource: **broken link removed**

There is plenty here to choose from: **broken link removed**

Those sheer bolts are exactly what I was talking about. The one's we got had an extra little nub of copper in one spot, you hit that with a hammer and it crimps the cable. Not as good as a true mechanical/hydraulic crimper but they never failed in the 300-1000amp cables that were run to the plating tanks.

Here's a link to how to do it with the types of terminals already linked. It's not complicated, copper is soft. Granted a true circular compression tool will give you better overall contact if you do it from multiple locations the compression is fine, especially if you solder fill for electrical conductivity.

I can't stress enough how important it is to properly seal the ends near the connector though, wire like this will absorb any liquids via capillary action up into the cable like a greedy little sucker. Although not as important for 'normal' environments even slight nicks in the insulation on the 00 cables that we used would over time cause the entire cable to corrode from the inside out, especially with the high currents and DC voltage impressed on it aiding the corrosion.

Hi,

The thing i was concerned about with using a torch is that copper wire gets 'burned' if the flame is applied directly to the copper. When copper pipes are soldered the torch is kept away from the actual joint and the heat conducts to the joint and that allows soldering.
But i guess with these big lugs i could heat the bottom and apply the solder to the inside of the lug...that might work ok.

The screw on lugs sound very good. I had forgotten about them too. Now all i have to do is find some crew on big alligator clips to connect to the battery with. It will be for a temporary inverter use not continuous.

I also realized that i have a heat gun that blows out 1000 watts or more. I suspect that could be used for soldering too but i have never tried soldering with a big heat gun, has anyone here ever tried that?

The main problem with heat guns is the air flow is too high for high decent soldering temperatures. I can just reach soldering temperature with a concentrator nozzel on mine, but this makes for a very fast airflow, enough to blow liquid solder away. Possibly useful for soldering something like this, but I think you'd be far better off with a propane torch if you just feather the flame in and out carefully.

The thermal resistance of the air to metal interface is so high that soldering anything of heavy gauge is going to be really problematic unless you have an airflow heated WAY beyond the soldering temperature because the thermal resistance of the copper itself is so extrememly low that it dissipates heat so well that even if the airflow is 350 degrees you'll never get the joint spot to reach soldering temperature because the bulk cable dissipates so much.

Hot air reflow requires relativly low airflow and very high temperatures relative to the soldering heat.

Hi,

Oh ok so i guess you tried this already. I havent tried it yet, but noticed that the hot air gun really puts out a lot of heat. I was thinking of heating from underneath and so using it like a torch. I'll give it a shot with something else and see what happens. I dont expect it to work too well with smaller wires though unless i make a soldering iron tip for it (he he) which would be interesting too.
I saw a really nice soldering gun online that goes up to 400 watts. A bit pricey though at $80 USD.

I did a smaller gauge wire crimp a few years back, number 8 gauge, and that's still working today. I think i used a vise grip

Hi,

The thing i was concerned about with using a torch is that copper wire gets 'burned' if the flame is applied directly to the copper. When copper pipes are soldered the torch is kept away from the actual joint and the heat conducts to the joint and that allows soldering.

Click to expand...

edit: you use a reducing flame, which is an oxygen-poor flame, which is bright yellow as opposed to blue (which is an oxidizing flame). the excess carbon eats up oxygen from the surface of the workpiece.
https://en.wikipedia.org/wiki/Oxidizing_and_reducing_flames

Possibly UncleJed, bu I wouldn't think so, most propane torches burn pretty clean and blue, I'd guess the wire filaments are so thin that they're vaporizing. There is a MASSIVE difference between soldering copper pipe and multi stranded wire.

I do heavy cable making fairly often all the way up 4/0 size for vehicle and equipment battery cable so for me 4 ga is rather light stuff!

The propane torch and solder method works just fine.

Pre crimp the lug in place with a hammer and chisel, not too hard, then use a low and light flame in a sweeping brushing movement to pre heat the cable lug and wire.

Give it a poke with the solder every few seconds and when its hot enough the solder will wick its way in right between the cable and lug.

Once your done let it cool then seal it with tape or shrink wrap.

Interesting issues as ever and I have made some HD cables with lugs, but that was a while ago (no crimps then).
Firstly, I wonder that you can't "beg/borrow" the hydraulic lug gear - maybe you have to "Hire" it?
Let's asume that is a solder-task, then:-
The important thing is to get the cable tinned quickly so the heat doesn't go too far up the copper, since this will draw solder. I think a small pot* of molten solder will have enough thermal capacity to "wet" the cable, but you will need a decent flux - this may need some experimenting....but you can practice and lop-off when done to perfect the technique.
The flux needs to be forced up the cable wires since there is no way to add more, once the cable is put into the molten "pot"
+Then, with the cable tinned it may be filed, so it fits the tinned lug. Now it's a matter of heating the lug and dipping the cabe end into a small amount of molten solder put in the lug.
The way this works is that the solder in the lug has enough thermal capacity to melt all the cable end when the molten (lug-pool) solder is displaced and it makes a good joint between the copper cable and the insides of the lug.

Some solder will be in excess and this should come out (falling on the floor, etc.(so prepare for this!). If the assembly is too slow then the danger is the excess solder is wicking up the cable wires and while the joint will be good, the cable-end will be very stiff and heavy.
Getting the assembly-speed right and the start-temperature is all a matter of "balance".

Finally you can finish the joint with "self-amalgamating tape" (this is a chemical forming tape, not sure what name you know it by....it forms a nice smooth finish. If you need to colour-code the cable (e.g. by the hole diameter of the lug), any prepared sleeve must be on the cable before the second end is finished. This is kept away from the lugs until finished and cool -

A retort-stand (or similar) should be provideded so the lug and cable do not move during the cooling process.

Good luck . . . . be safe with hot things.


* If you have a traditional solder-pot this will be made easier, but you can use a disposable pot containing much less solder - something about 2-3 times the diameter of the trimmed cable end, I'm guessing.

Have you tried a ganged battery clamp, like those found on tow trucks? Typically, one tow truck battery has a ganged clamp running a wire to a relay for frontal boosting. The relay is switched on by the driver, and includes a gauge to monitor current draw.
A performance car shop could also be helpful, if you can safely use an insulated grounding block for your application. Use non-conductive hardware to attach the grounding block to the fender wall.

Hi,

No i havent tried a ganged battery clamp, you mean like the ones with the bolt or different?

Hi Al,
For lugs all I've ever used was a butane flame, basically the lug should suit the wire gauge. Grab some Bakers solder flux then as your gently heating the lug pour some solder flux in the pot then quickly dip the wire in the lug hole. Then keep heating the lug until a pool of solder is motlen just below the to of the lug hole, place the wire in the hole and steady until cool. I used that method for connecting my batterybanks and no problems ever since and I just used some heatshrink to cover the joint. This was on 400 amp welding cable and to code the wire a cheap can of red and black spray paint did the job.

Regards Bryan

Crimping before soldering will always provide a far superior mechanical linkage to soldering alone, especially to those without soldering skills as good as your bryan1. Especially in high current linkages if something bad happens and the solder liquefies or even softens significantly it will fail mechanically.

Cables made with crimping are for 100% or even rough duty service where it needs to be stronger than is theoretically required.

Your 400 amp welding cable would fail utterly in a 300 amp constant current scenario. Welding duty cycle has to be taken into account and I'm one to recommend designing for fail safe. Design for constant use, or higher! It makes for lower failure in the end.

Hi,

I've read that crimping is better than soldering, but i like both

Some good ideas here. I like the part about painting the ends red and black very much. The reason is it is so easy to make a mistake when you're in a hurry. I just hooked up a new triple output cigar lighter plug the other day and wouldnt you know it, i forgot which lead was positive, so i of course hooked it up backwards the first time. Checking it with something that needed a ground (one the ground output part of the receptacle) i found that it was wired backwards, so had to go and swap the two connections. I meant to tape them with colored tape but i guess that can come off.
I have some black spray paint and i think i have some red around somewhere too, just have to find it now