Build your own CD battery tab welder for about $100.00+-

[Jeremy Harris]

I don't think there is a practical way of doing a working dual pulse welder with SCRs. Sure you can generate two pulses, but they will not be structured in a way that is useful.

I 100% agree. I spent a fair bit of time looking at ways to commutate big SCRs, so that I could have decent pulse width control, but two things make it hard to do. The first is that the commutation current has to momentarily exceed the conduction current, so it's a pretty brute force way of doing things. Secondly, the time it takes to commutate an SCR means that you have a limited ability to practically control the pulse width anyway, at least for a low voltage CD topology. I think the SCR plus commutation would work OK for a high voltage, transformer coupled, resistance welder, as the currents would be lower and the switching times faster, but the transformer is really the sticking point with this topology, at least for a DIY approach.

SCR welders are rude, crude, and socially unacceptable beasts. Sure, they can blast two pieces of metal together, but they do not have enough finesse or control to do it properly.

A lot of people, me included, would take issue with the vigour with which you've made this point. I've made hundreds of really good welds between nickel strip and steel battery cans with my welder (which has 20 paralleled 97,000uf, 20V, low ESR capacitors and a single big SCR). Others have done the same.

Sure, if I was going into business welding packs, then I'd build a FET switched welder - in fact we discussed it in this thread about a year or so ago and one member built one. I don't think that you need anything fancy to build a dual pulse FET switched welder either, my test breadboard used three 555 timers with variable pulse width, each triggered from its predecessor, one for initial cleaning pulse width, the next for pulse delay and the final one for weld pulse width. The only other control was the charge voltage setting. Although I didn't bother to finish this welder (because the single pulse SCR one worked so well and did the job for me) I've no doubt that it would have worked. It was just a complete overkill for the job in hand and out of keeping with the spirit of this thread, which is focussed on a cheap and cheerful way to build a welder, hence the $100 in the title.

Jeremy

 

[texaspyro]

I don't think that you need anything fancy to build a dual pulse FET switched welder either, my test breadboard used three 555 timers with variable pulse width, each triggered from its predecessor, one for initial cleaning pulse width, the next for pulse delay and the final one for weld pulse width. The only other control was the charge voltage setting.
Jeremy

That is certainly true. I'm a digital sort of guy, so I used the AVR micro to generate the pulses instead of 555's. It can easily be done in under 100 lines of code with a simple micro or with 3 555's and a variable power supply.

Such a welder will definitely get the job done (and much better than an SCR welder will). And a basic FET welder really isn't much more complicated than an SCR welder... but a person not familiar with electronics has a much better chance of getting an SCR welder up and running. I built my SCR welder in under 15 minutes. It took a couple of hours to get the basic FET welder together and generating pulses.

The other 5000+ lines of code in my FET welder are mostly user interface, fault monitoring, and gratuitous gee-gaws.

One thing that you can't do with just 555's is generate the pulses based upon their energy content. For that, you need to monitor the energy going out the cap in real time and terminate the pulse when the desired energy has been spent. My FET welder does let you weld by time and/or energy.

Other things you can do with a micro and a few thousand lines of code: You can store lots of pulse setups in EEPROM. You can control the thing from a touchscreen or computer. You can interface with pneumatic or mechanical force controlled weld helds. You can use force sensitive resistors on hand held electrodes to only fire the pulse when the electrode force is correct (electrode force is VERY important for getting good welds). You can monitor for just about any fault condition and try to keep the magic smoke in the components and the juice in the capacitors. You can record the capacitor voltage every 100 microseconds during a weld cycle and calculate and graph the weld voltage, energy, current, power, and resistance. You can know if anything abnormal went on during a weld. You can automatically shutdown if left unattended. You can measure a capacitor to within a millifarad and calculate its ESR. You can play a jaunty tune.

All totally superfluous to the task of joining two pieces of metal in holy wedlock.... but way cool... and very important if you want to know that the weld that you just made is what you thought it was and is identical to the last one that you made. Or if you want to join two metals that don't like each other.

 

[The Mighty Volt]

When will Fritz have the boards back in stock?

 

[texaspyro]

When will Fritz have the boards back in stock?

You'll have to ask Fritz that to be sure, but I think he is through building boards. He did a second run of MOSFET boards a while back and called it quits in building boards. You'll have to buy his artwork package (cheap) and have the boards fabbed yourself (not so cheap).

I purchased a couple of his MOSFET boards that I was going to use in some prototypes, but wound up using my own boards. If somebody is going to build one of his units (or their own MOSFET welder), I can supply those boards at his price which would be a whole lot less than having a board or two fabbed.

 

[The Mighty Volt]

When will Fritz have the boards back in stock?

You'll have to ask Fritz that to be sure, but I think he is through building boards. He did a second run of MOSFET boards a while back and called it quits in building boards. You'll have to buy his artwork package (cheap) and have the boards fabbed yourself (not so cheap).

I purchased a couple of his MOSFET boards that I was going to use in some prototypes, but wound up using my own boards. If somebody is going to build one of his units (or their own MOSFET welder), I can supply those boards at his price which would be a whole lot less than having a board or two fabbed.

Hi there, thanks for the information, I might buy his schematic, I have a friend who is a real electronics expert and will try to rouse his interest.

 

[chemosavi]

All of this info is quite fascinating and I've learned a lot I didn't know before but I'm not at all convinced a fancy smancy dual pulsed welder does most jobs any better and maybe not as well as a regular transformer based AC welder that costs almost nothing. Owning both types (single pulsed 230ws Sunstone) I find the AC timed machine much more reliable in terms of both weld quality and repeatability. But maybe this is more about making something cheaply that normally costs a fortune instead of getting a job done. I dunno. Anyways thanks for all the incredible explanations, especially Jeremy and Texas fire nut. What I make with my machines....http://www.howeart.net

I could have saved a lot of money and time if I could have tried the same functions with the following machines. ( And some supposedly very knowledgeable folks will deny many of these to be possible even though they are)

Resistance Weld (also known as Battery tab weld)
Cross wire weld
Fusion weld ( as in stud gun, i.e., take a rod and stick it next to another piece of metal and hit it with the juice, also known as thermocouple weld and insulation pin weld)

#1-Dual pulsed 1000ws capacitive discharge. Price retail $4,700.00 - $20,000.00
#2- Single pulsed capacitive 1000ws discharge.
#3- DIY versions of above. $100.00 - ?
#4- 66,000uF CD stud gun @200V (1,600ws) $2,000.00 -$4,000.00
#5- AC Arc stud gun
#6- 1.5KVA and 2.5KVA hand held Miller resistance spot welder (115v and 220v respectively) $500.00 - $900.00
#7- 1.5KVA DIY MOT resistance spot welder. $0.00 - $100.00 (timer and relay additional)
#8- 10 KVA stationary resistance spot welder. $900.00 - $9,000.00

But maybe it's got to be like they say: Knowledge is expensive.

 

[tonybikes]

Sure, if I was going into business welding packs, then I'd build a FET switched welder - in fact we discussed it in this thread about a year or so ago and one member built one. I don't think that you need anything fancy to build a dual pulse FET switched welder either, my test breadboard used three 555 timers with variable pulse width, each triggered from its predecessor, one for initial cleaning pulse width, the next for pulse delay and the final one for weld pulse width. The only other control was the charge voltage setting. Although I didn't bother to finish this welder (because the single pulse SCR one worked so well and did the job for me) I've no doubt that it would have worked. It was just a complete overkill for the job in hand and out of keeping with the spirit of this thread, which is focussed on a cheap and cheerful way to build a welder, hence the $100 in the title.

Jeremy

It my first try i put 3 555 in cascade but i cant have a good range of adjutement on hi speed timing so what is your setup resistor cap and potensiometre.

 

[The Mighty Volt]

I just got a quote of $24.20 each per unit of 100,000 uF capacitors.

Basically I would need 20 of these to make up 2F, which is quite a few bob.

http://www.tedss.com/2020006441

 

[texaspyro]

I just got a quote of $24.20 each per unit of 100,000 uF capacitors.

You can pick up the Scosche ECAP1 caps on Ebay for $36 ea, buy-it-now... I think you will find a single cap will work well, but you can buy two (or more) and connect in parallel). They are rated at 20V... try to avoid running them above 16V since they don't say if that is a working or surge voltage. I have run them at 20V without problem, YMMV...

If you just gotta use more than 16-20V, buy four and connect in 2-series/2-parallel (with a 470 ohm or so 1-watt resistor across each of the caps (or a 220 ohm resistor across each of the paralleled pairs that are connected in series). That will yield a 1F 32V+ cap.

Remember to strip the voltmeters off and bolt directly to the capacitor terminals...

 

[The Mighty Volt]

I just got a quote of $24.20 each per unit of 100,000 uF capacitors.

You can pick up the Scosche ECAP1 caps on Ebay for $36 ea, buy-it-now... I think you will find a single cap will work well, but you can buy two (or more) and connect in parallel). They are rated at 20V... try to avoid running them above 16V since they don't say if that is a working or surge voltage. I have run them at 20V without problem, YMMV...

If you just gotta use more than 16-20V, buy four and connect in 2-series/2-parallel (with a 470 ohm or so 1-watt resistor across each of the caps (or a 220 ohm resistor across each of the paralleled pairs that are connected in series). That will yield a 1F 32V+ cap.

Remember to strip the voltmeters off and bolt directly to the capacitor terminals...

Hi there, was it not your good self who advised us against using these audio caps?? I dont want to be argumentative, but what is so different about these audio caps? Thanks. 8)

 

[texaspyro]

Hi there, was it not your good self who advised us against using these audio caps?? I dont want to be argumentative, but what is so different about these audio caps? Thanks. 8)

Not at all... I mentioned three specific car audio capacitors that I tested multiple units of and found all specimens to be legitimate and quite suitable for welder use. They were real 1 farad units with good ESRs (around 1 milliohm).

The Scosche units were one of them and a seller on Ebay has them for a good, non auction price. The Rockford RFC1 caps are also quite good (even lower ESR than the Scosche) and can be had for less than $50. Also, a Monster Cable 1F cap tested very good.

The Volfenhag ZX-3 also tested good. I have mixed feelings about it. It is a 1F cap, but they sell it as 3F! Works for welders... hanky-panky in the specifications. I'd prefer to send my business to companies that don't scam you on the specs. Also the ZX-3 is speced at 20V/24V surge... very good if it actually meets that voltage spec. Something tells me if you are being shorted on the capacitance, the voltage spec is more than likely off. I've run a ZX3 at 20V for a long time without any problems. Have not tried it above that. Their ZX-2.2 measured out at 0.5F with poor ESR. Not welder-worthy.

 

[texaspyro]

When considering just how much capacitor you really need... a GOOD 1F cap charged to 19V can easily blow a hole through .032 aluminum. Also does wonders to 18 gauge steel... Makes a satisfying POW! in the process.

 

[davidh]

with all 37 pages of tech.information, and the orig. posters info, im building a dual welder.

im using a 1.7 f. audio and a 5.0 f. audio capacitor and one 200a and two 200a diodes from big welders to release the powere of thse thnigs.
i intend to use a reed switch to open the 5.0f capacitor by tapeing it to the lead of the 1.7f c.
the orig trigger will be a pair of 1.5 double a's controlled by a pair of microswitches. one for the trigger circuit and the other to shut off the pwer supplies. one power supply is 12 v the other is variable from 3 v. to 24. that one i will try on the smaller capacitor

as you can tell, im a electronic dud, but i have faith in what im reading here.

i have made my electrods from hard copper from the windings of an old solider gun, its at least elqual to the ground wire
on my house. no 4. buried in some insulating round stock i had laying around, and soldering my no. 8 copper wire to.

the cable off the diodes is about no 4, and i intend to connect that to about 3 feet of the no. 8.

hope the heck it works. . . comments extremely welcome. . . .

thanks, davidh (the old guy)

 

[texaspyro]

im using a 1.7 f. audio and a 5.0 f. audio capacitor
i intend to use a reed switch to open the 5.0f capacitor by tapeing it to the lead of the 1.7f c.

First off, your audio caps are almost assuredly crapassators. Utterly useless for welders. I know of absolutely NO 5 farad caps that are not "hybrid" caps that use ultra-high ESR "carbon" capacitors to boost their capacitance ratings. I have now tested over 15 brands of car audio caps, and only three devices came ANYWHERE near meeting their published specs. Name brands are no assurance of a good cap. One other brand had usable caps, but they were at least a factor of three less than their published specs.

Also, high capacitance capacitors tend to have high ESRs. ESR is the equivalent series resistance of the capacitor. ESR saps energy from the weld pulse before it even gets out of the capacitor. You are much better off paralleling three 1F caps than using a single 3F cap.

If you parallel three caps, the ESR will be 1/3 that of a single cap. Plus, all things being equal, high capacitance caps have much higher ESR than lower capacitance caps. A 3F non-carbon/non-"hybrid" cap, if you could find such a thing, might have an ESR of 3 milliohms. 3 good 1F caps in parallel might have an ESR of 1/3 a milliohm... 10 times less. A hybrid/carbon 3F cap might have an effective ESR of over an ohm... 3000 times higher!

If you are "opening" the 5F cap with a reed switch, the switch will be vaporized by the welding current. Reed switches can switch thousandths of an amp. The cap will generate thousands of amps. If you are firing the second SCR with the reed relay, you are wasting your time.

Attempting to simulate a dual pulse welder with SCRs is actually less than useless. SCRs cannot control the current to the degree needed to do the dual pulse properly. An SCR will dump all the power out of the cap before it turns off. For a dual pulse welder to work properly, the first pulse must be controlled to the point where it will not cause the welded material to even mildly stick together. If the first pulse of a dual pulse causes the material to tack together, the joint resistance will be lowered to the point where the second welding pulse cannot do its job of generating enough heat to do a proper bond. You are MUCH better off just doing a single pulse welder with SCRs. And make damn sure your cap is what you think it is...

 

[Jeremy Harris]

I did look at making a dead simple dual pulse welder, with two capacitors and two thyristors. In theory it should work OK, albeit with the lack of pulse width control that all simple welders like this have. I ran into a triggering problem though, one that I could have fixed with a bit of time and effort but which I didn't need to, as the single pulse worked fine for my needs.

The way I set up the dual pulse was to have two of my 97,000uF 20V capacitors hooked up to the first thyristor, charged by my bench supply via a changeover relay wired to the trigger button (this disconnects the charging supply during the weld). I wired up the remaining eighteen 97,000uf capacitors to the other thyristor and fired it via a simple 555 timer triggered by the trigger pulse.

What I hoped would happen would be that the first thyristor would fire immediately the trigger was pressed and the second one would fire a short time later, when the 555 pulse finished (I fitted a capacitively coupled transistor to the 555 output to invert it and provide a big enough drive current pulse to the second thyristor). Once or twice it did work OK, but most of the time the high dV/dT, or dI/dT, caused the second thyristor to fire prematurely.

The false trigger problem was almost certainly down to the layout and EMI, not really surprising when you look at the high currents flowing around the place. I'm sure I could have got it to work reliably with an hour or two of fine tuning, but I couldn't see the point, as all I wanted to do was weld up 64 Headway cells and the thing worked perfectly for this job in single pulse mode. I just stripped out the delay circuit and second thyristor and wired all the capacitors into one bank.

Sometimes, the dead simple approach is exactly what's needed. In my case I was building one battery pack, so only needed something good enough to work for two or three hours and make acceptable welds between nickel strip and steel. My crude welder did that admirably, in fact far better than I expected, so I couldn't see the point in investing more time and money in something more technically advanced, tempting as it was.....................

Jeremy

 

[texaspyro]

I did look at making a dead simple dual pulse welder

I added a "full auto" mode to my welder. You only need to set the energy and/or time of the first pulse. From that it calculates a reasonable pulse delay and second pulse energy/width.

Also, I have not seen many commercial dual pulse welders where the pulse delay value can be set by the user. I did find one reference that implied using a pulse delay value based upon the width of the first pulse.... that's what mine does in auto-delay mode.

 

[fabianix]

maybe my thyristor is dead..seems that it is alway activated, also without the trigger. I cannot put the second electrode onto the cell because it literally explode in a lot of sparks, I think the PN junction is welding itself

this is the second thyristor that I have broken, the first one was the SILEC IBM 227 A 2395852 3.36, the second one is SILEC IBM 227 A 2395852 3.02..
no datasheet available on the net but I think they was AT LEAST 100Amps
I'm using my upgraded spot welder (see my previous pictures) with two 3F Caps in parallel, 6F total. The trigger is a li-ion cell of 3,7V
I don't know what happen...

 

[The Mighty Volt]

Okay, just wanted to add that I bought up 4 0.5F Rockford-Fosgate capacitors today, and will have them for testing in 10 days or so. Each cap is supposedly super low resistance and a true 0.5F capacitance. It was the best I could do between the super expensive electrolytic capacitors on one hand and the usual crapassitor junk on the other. I will parallel them and see what happens.

 

[texaspyro]

Okay, just wanted to add that I bought up 4 0.5F Rockford-Fosgate capacitors today, and will have them for testing in 10 days or so. Each cap is supposedly super low resistance and a true 0.5F capacitance.

I haven't tested their 0.5F caps, but their 1 farad RFC1 / RFC1D are rather nice... consistently the lowest ESR that I have seen and capacitance variations of less than 5%... and I have a dozen of them now. I would recommend keeping the voltage to 16V or less (unless you do a series/parallel stack).

Their "surge" voltage is rated at 20V. I have charged them to 20V without any problems, but you can get a rather significant inductive kickback when the pulse ends due to the lead inductance. This is not as much a issue with SCR welders as with FET welders because the SCR welder completely drains the capacitor. By the end of the pulse, the voltage and current is rather low and the energy stored in the leads has had a chance to dissipate.

On FET welders, you can stop the pulse while very high currents are still flowing. The inductive kickback can be rather large. On my FET welder, I installed some serious transient voltage suppression devices... the first cut of which got vaporized.

 

[The Mighty Volt]

Okay, just wanted to add that I bought up 4 0.5F Rockford-Fosgate capacitors today, and will have them for testing in 10 days or so. Each cap is supposedly super low resistance and a true 0.5F capacitance.

I haven't tested their 0.5F caps, but their 1 farad RFC1 / RFC1D are rather nice... consistently the lowest ESR that I have seen and capacitance variations of less than 5%... and I have a dozen of them now. I would recommend keeping the voltage to 16V or less (unless you do a series/parallel stack).

Their "surge" voltage is rated at 20V. I have charged them to 20V without any problems, but you can get a rather significant inductive kickback when the pulse ends due to the lead inductance. This is not as much a issue with SCR welders as with FET welders because the SCR welder completely drains the capacitor. By the end of the pulse, the voltage and current is rather low and the energy stored in the leads has had a chance to dissipate.

On FET welders, you can stop the pulse while very high currents are still flowing. The inductive kickback can be rather large. On my FET welder, I installed some serious transient voltage suppression devices... the first cut of which got vaporized.

Hi Pyro. Thanks for the advice!!

I found two 1F Monster Cable Caps but the guy was asking stupid money and even stupider postage to Ireland. It would have cost around £400Stg to buy them and then get them here. That's Computer Capacitor territory.

Part of what made me go for the 0.5F Rockfords was the opportunity to mate several smaller capacitors in parallel. That and the fact that buying 4 small ones actually came out cheaper than buying 2 big ones.

Anyways, the language used by the seller was encouraging- he specifically referred to low ESR and to "true capacitance".

CHe

 

[texaspyro]

The trigger is a li-ion cell of 3,7V I don't know what happen...

Are you current limiting the SCR gate signal? If not, you will fry the device. Try a 10 ohm or so resistor in series with with Li-ion cell.

Also, I would skip using a separate gate voltage supply. Trigger the SCR from the capacitor voltage (via a single pole/double throw "changeover" relay).

The relay coil is energized by connecting it across the charger voltage through the firing button. The relay common terminal connects to the capacitor + terminal/positive electrode. The normally closed relay contact connects to the charger voltage (usually via a current limiting resistor... maybe 5 ohm / 20 watt). The normally open relay contact connects to the SCR gate through a current limiting resistor. I would start with a gate current limiting resistor of around 50 ohms/2watts.

The SCR cathode connects to the charger "-" voltage and capacitor "-" terminal. The SCR anode is the negative electrode.

 

[texaspyro]

Anyways, the language used by the seller was encouraging- he specifically referred to low ESR and to "true capacitance".
CHe

Ah, yes... The Chant of the Sacred Capacitor... all cap makers fervently utter it... VERY few deliver on its promise.

I have seen several MAJOR manufacturers promise you a 3F +/- 5%, 1.5 milliohm capacitor which actually measures 0.25F and over 3 milliohms. Fraudulent capacitor specs are BY FAR the norm. Real capacitors are scarce beasties indeed.

I do trust Rockford to deliver on their promises. Four caps in parallel should make an impressive KAPOW! Don't waste their potential with wimpy interconnects.

 

[texaspyro]

Speaking of wasting your capacitor's potential... just how much of those juicy joules make it out of the capacitor and into the weld? Probably a LOT less than you may think. TINY resistances quickly add up and sap the available weld energy.

Here are some numbers from my FET welder. Cap ESR 0.33 milliohms. FET resistance .17 milliohms. Misc interconnect resistances maybe another 0.5 milliohms. Total internal welder resistance around 1 milliohm (wanna bet yours will be more... I have silver plated interconnects and cable crimps done with over 8 tons of pressure) At 20V on the caps, the best it can do is 20,000 amps.

Now add two 3 foot 4 AWG genuine pure copper welder cables... 2 milliohms. You did get the real pure copper cables that you paid for? Perhaps... perhaps not. Some cables that I measured were three times that resistance. They sure looked like copper. Said so on the spool too. Even the tooth fairy vouched for their quality.

Cables over 4 gauge tend to be unwieldy for hand held use... 1 gauge wire might cut that resistance in half. You are down to 6700 amps. Now connect those cables to some electrodes. Oops, there goes another 0.5 milliohms and the current is down around 5500 amps. If one fourth of your energy gets to the electrode tips, you are doing rather well...

These are all pure resistances. There are other energy sappers along the way. Capacitor ESL (equivalent series inductance) and the weld lead inductance also take a heavy toll. Get some metal near the leads and watch your energy disappear into thin air and wind up heating that metal.

One thing that lead inductance does that can be good is that it tends to level out the current pulse. A perfect capacitor discharge is an exponentially decaying pulse. Inductance tends to inhibit the flow of quickly changing dynamic currents. Energy gets stored in the inductance when the current is quickly changing and gets released later.

What shows up at the electrodes will be a pulse of lower peak amplitude, but the energy cut from the initial peak gets redistributed to the rest of the pulse. So instead of a pulse that starts at 6000 amps and falls rapidly/semi-linearly to a few hundred amps then decays slowly to 0, might see a pulse that starts out at 3000 amps, falls slowly to 2000 amps, then drops to 0. Of course, you have to pay a toll to the gods of electrical friction for the service.

 

[The Mighty Volt]

Speaking of wasting your capacitor's potential... just how much of those juicy joules make it out of the capacitor and into the weld? Probably a LOT less than you may think. TINY resistances quickly add up and sap the available weld energy.

Here are some numbers from my FET welder. Cap ESR 0.33 milliohms. FET resistance .17 milliohms. Misc interconnect resistances maybe another 0.5 milliohms. Total internal welder resistance around 1 milliohm (wanna bet yours will be more... I have silver plated interconnects and cable crimps done with over 8 tons of pressure) At 20V on the caps, the best it can do is 20,000 amps.

Now add two 3 foot 4 AWG genuine pure copper welder cables... 2 milliohms. You did get the real pure copper cables that you paid for? Perhaps... perhaps not. Some cables that I measured were three times that resistance. They sure looked like copper. Said so on the spool too. Even the tooth fairy vouched for their quality.

Cables over 4 gauge tend to be unwieldy for hand held use... 1 gauge wire might cut that resistance in half. You are down to 6700 amps. Now connect those cables to some electrodes. Oops, there goes another 0.5 milliohms and the current is down around 5500 amps. If one fourth of your energy gets to the electrode tips, you are doing rather well...

These are all pure resistances. There are other energy sappers along the way. Capacitor ESL (equivalent series inductance) and the weld lead inductance also take a heavy toll. Get some metal near the leads and watch your energy disappear into thin air and wind up heating that metal.

One thing that lead inductance does that can be good is that it tends to level out the current pulse. A perfect capacitor discharge is an exponentially decaying pulse. Inductance tends to inhibit the flow of quickly changing dynamic currents. Energy gets stored in the inductance when the current is quickly changing and gets released later.

What shows up at the electrodes will be a pulse of lower peak amplitude, but the energy cut from the initial peak gets redistributed to the rest of the pulse. So instead of a pulse that starts at 6000 amps and falls rapidly/semi-linearly to a few hundred amps then decays slowly to 0, might see a pulse that starts out at 3000 amps, falls slowly to 2000 amps, then drops to 0. Of course, you have to pay a toll to the gods of electrical friction for the service.

I got me some of the fattest, softest, multi-strand copper you have ever seen. I will post a few fotos...this stuff is pure gold. Well, copper.

 

[texaspyro]

I got me some of the fattest, softest, multi-strand copper you have ever seen.

Probably not... I had a friend that made some jumper cables for his truck out of military surplus starter cable for tanks. It was over an inch in diameter, weighed a ton, was more flexible than wet spaghetti. The conductors looked like Litz wire. The insulation looked like some sort of silicone based material. It felt... unnatural...

And again you have to be careful about what you are actually getting. Unless you can actually measure the resistance, you never know what you have. The slimy tricks that a lot of the car audio industry and shady Chinese suppliers have been pulling has made me VERY skeptical about such things... " Don't trust... Verify!"

The 4 gauge Scosche EFX Flux cable that I am using right now is good stuff. It has the proper resistance. You can coil it into a two inch diameter coil. Part of the flexibility seems to come from the fact that the wires are not gripped by the insulation. You can feel the insulation sliding over the wire bundle.

Scosche also makes 0 gauge cable that I may try. That stuff is over 50% fatter than the 4 ga. It would have around 1/3 the resistance of the 4 ga cable at the expense of twice the weight and considerably less flexibility. It would cut the total external resistance of the welder to around a milliohm and boost the available weld current back up to around 10,000 amps.

The Excelene welder cables that I have tested are also very good. Not as flexible as the Scosche stuff, but is real copper. I've only seen it in black. I like my cables color coded for polarity.