Spot welding Copper / Copper Nickel / Copper Stainless Steel Sandwich

[SternWake]

With all the new high power Tabless power cells on the market, and even higher power and higher capacity cells promised in the near future, it seems the electrical bottlenecks will not be the cells themselves, but the parallel and series connections between cells and P groups.

I have built 3 small Esk8 batteries so far, in the last 2 years, using a cheap ‘purple’ spot welder using 0.1mm copper, 0.1 Nickel plated steel sandwich. I used copper nickel sandwich even though my builds are low power, in comparison to most builds on this forum.

I personally can’t stand the thought of electrical resistance abusing battery capacity to heat the cells and interconnects, and dropping the voltage reaching the ESC.

I am certainly no professional battery builder, nor any authority on this subject, and I do not wish this to be ‘My’ thread, even though I plan on contributing a lot to it as I gain experience, and perform experiments, and see what is possible with the equipment now at my disposal.

I don’t know if disclaimers are required, but ‘do so at your own risk’ is implied.

Welding copper takes a lot more energy than welding pure nickel, and I think this this thread should also be about the equipment required to successfully achieve solid low resistance welds, as much as the techniques required to Safely do so.

There will be some inevitable crossover with the Battery builder’s thread. I don’t know how best to keep things organized and clean for future reference, nor do I wish to task others with doing so.

I now have an AwithZ P20B 14.6kW spot welder, thanks to Nelvick @DIY500AMP.COM, whom I believe to be a refreshingly honest and honorable individual, traits which have become exceedingly rare in the world today.

His store carries most all the latest desirable power and energy cells, and the welders, and various battery building supplies and tools.

He has donated the latest difficult to acquire and exciting cells to @Battery_Mooch, and others, for professional testing, and we are all better informed because of their efforts.

I admit heavy bias, but ask you to consider supporting him and his store, when you next need cells and related battery building equipment.

DIY500AMP - Premium Battery Cells & DIY Battery Building Materials

He has all sorts of cool tools and toys, and is into 3d printing, and all things DIY, wants to do things right, and gratefully takes advice without attitude or ego getting in the way.

It would be great if this thread is not just about welding copper, but also shares the latest and safest battery building practices, and techniques, with contributions and criticisms from those with Vast experience building batteries and who helped to refine what currently is considered best practice and technique for Esk8 batteries.

I personally get a bit too excited regarding these Tabless power cells, even though I don’t have the ability to ask them for their full potential.

I will next be building a 10S1p Eve 40PL pack with 0.2mm copper / 0.1mm nickel plated steel sandwich, for a lightweight grocery getter, kayak tow vehicle, and backup rolling sanity device.

I intend to first explore the ability of the new to me AwithZ spot welder, and I will be posting here regularly on my experiments and testing and techniques, rather than only in my rambling, personal thought collating, TLDR, modified premade junk thread.

I have a pretty good camera to take macro photos, and welcome criticism and advice, and input.

I will also do my best to assuage the curiosity of others regarding the AwithZ P20B welder’s capability. AwithZ offers many different models of capacitor based spot welders, the the P20B is the second most powerful at 14.4kW. They have one that is close to 70kW, and 3 or 4 welders in between, and I hope they prove durable.

[A-damW]

Following.
Do you mind discussing other welders, as long as it is involves copper?

I have a Malectrics welder and some Maxwell 3000F supercaps I want to try w/copper.

[glyphiks]

Hell yeah. Welding copper is essential to getting the most out of these new cells. Exciting times!

[SternWake]

@A-damW

Do you mind discussing other welders, as long as it is involves copper?

By all means. Please do.
There are some other welder options on the market like Sequure (spelling?)and Glitter that have the power to weld copper.

Let this thread be about the means as much as the end, in my opinion.

[SternWake]

Ok, I am set up in the Air conditioning, as opposed to my insanely hot workshop in the garage, and experimenting with the AwithZ P20B, and 0.2mm copper, No nickel sandwich, no flux.

@glyphiks and @Pecos showed interest in not having to use nickel or nickel plated steel sandwich, with Pecos coining the ‘raw dog copper’ verbiage and future band name, in another thread.

I worked up the gears until it started sticking, slightly, and was up over gear 500 (999 max) before that occurred. Closer to gear 650 one electrode started having an almost weld, and at gear 690 this just blew right through the copper, into the cell can, puncturing it, and the other electrode’s weld was weak, at best.

The electrode which blew through the copper had part of the steel can stuck to the tip, and the diamond file provided with the welder, was struggling to remove it.

I smelled the sickly sweet smell of electrolyte and got a different cell.

I used a small smidge of Nelvick’s copper welding flux/Brazing paste, and used the same settings. 0.2mm copper, no Nickel, and two solid welds occurred.

The copper tore when removing the strip, but in my opinion 0.2mm copper is just not strong enough on its own. I’ll estimate it takes well more than twice the force to remove 0.2 copper with 0.1mm Nickel plated steel on top. If there is never any physical stress placed on the 0.2mm copper I guess it could be considered adequate. i think if one wants to skip the sandwich, Aim for 0.25 or 0.3mm copper.

Here is a link to the copper flux/brazing paste I am using.

Flux for Copper-to-Copper Spot Welding (100g)

I am still working on the depth of field and focus with my camera. I am out of practice. Expect higher quality images in future posts. The flash made it look like the weld on the left is silver on top, but it is not.

That weld occurred using these welder settings. Again that is 0.2mm copper, no Sandwich, using flux.

Here is the copper strip once cleaned of the excess flux. The Flux tins the copper in close proximity to the weld. I cannot tell if this also stuck to the cell’s can. I honestly cant tell if it did. It does not look like it. Perhaps it can only chemically bond with copper.

I Did not really experiment with the preheating duration, not the pulse interval.

I do not have any 0.3 copper, but I can try stacking 0.2 with 0.1, and see if it works. I am honesly reluctant to not use the flux, as i only have 5 test cells left, am in my bedroom, and puncturing the can again is not something I look forward to experiencing again.

Some other observations, is that the welders 9 volt DC 15 amp power supply has a fan inside of it. It runs briefly after a weld.

I broke out new welding tips. At first I tried experimenting welding a 0.2 Nickel Plated Steel ( but non magnetic?) buttontop to some 0.2 copper., then welding both to the cell positive, and folding the copper over the button and welding it to that. The worn electrode tips are too fat for this.

I basically failed in this endeavor, and decided to table it for now. If I tried it on the Ampace JP30 instead of a 0.0631volt test cell I’d likely have ruined it in my haste. I have a flashlight that needs a button top cell. It does not require a JP30, but I couldn’t resist ordering two of such an incredible cell when I ordered the flux.

As the electrodes wear, their surface area increases, and depending on how one files them, their shape will change. This can lead to significant variances in the power required to achieve consistent welds.

I think it would be nice to have a way to insure the same tip shape and diameter of the electrode tips, something like a manual pencil sharpener.

In my ‘junk’ thread I determined this welder could do 0.2mm copper, 0.1mm nickel plated steel at gear 990 with no flux, and gear 790 with the flux. With the Flux the welds also appeared wider and seemed to require more force to peel off the can.

Welding with the flux, has some smoke happen. I did not notice the pink color Nelvick mentioned in his videos, but did stick my nose into it for a light sniff and it is not excruciatingly unpleasant, but I’d not want to be making huge amounts of it indoors.

I’m gonna grab another beer and see if stacked 0.1 and 0.15mm copper, no nickel sandwich, but with flux is possible and if so how strong it seems. I guess I can try 0.2 and 0.1 stacks too.

[SternWake]

Here is 0.15mm copper atop 0.1mm copper, with flux, gear 850, preheating 0.15ms, 04ms interval, double pulse.

The peel off strength was good, but obviously 0.25mm stacked copper felt a bit flimsier than solid 0.25 copper would.

I think this is very Viable nickel Sandwich free option with this welder.

The other copper bits on the cell were half hearted attempts with 0.1mm copper atop 0.2 and gear under 750. I wasn’t feeling it, then decided to go down 0.05mm.
I was trying the flux between the copper layers too which was unnecessary.

I had never considered being able to skip the nickel plated steel sandwich. i thought it was absolutely necessary. Conductivity wise 0.25 copper beats 0.2 copper with 0.1 nickel plated steel on top, but the latter takes a lot more force to peel off the cell, but how relevant is that if the welds are strong and the material has to tear?

[glyphiks]

I wonder if the flux would contribute to any sort of corrosion to the cell at all

[SternWake]

Nelvick says it is not corrosive.

I am experimenting with dual stacked 0.15mm copper at gear 972

One weld is smaller than the other.
I hypothesize that this happens when the welder is at the limits of its power or set just below the power required to weld the material.

I could try increasing the preheating, triple pulse, and boost it upto gear 999, but even if it works, I dont want to build a battery using its absolute max power every weld.

But I think it is safe to say with the P30C, that one can weld 0.3 copper no sandwich, with Flux well below its max power…
The P30C is 24kW,
My P20B is 14.6kW
The P60F is 29.2kW
The P90C is 56.8kW
The P120D is 69.2kW

[SternWake]

Anybody have an idea to test whether it is corrosive, that doesn’t take 6 months+?

Here is double stacked 0.15mm copper.

Here I Bumped up the gear, preheating, and added a third pulse, but the weld on the right is still a bit less than the on the left. Still adhered, just not as wide.

Sorry this is a bit out of focus, and please ignore the cotton from n alcohol soaked swab used to remove the excess flux.

Overall, I think this welder is pretty impressive. I never expected to be able to weld copper without nickel or nickel plated steel on top, much less 0.3mm.

0.3mm copper is just barely possible at near max power, or I should say dual 0.15mm stacked, whether there is any difference I can’t say. The preheating can be raised to 50ms

I’d like to have 0.25mm copper, and see how that feels when folded over the double fishpapered cell shoulders. My previous 0.1mm copper battery builds truly needed the 0.1 nickel plated steel on top and those still felt pretty flimsy.

Having to solder series connections, with copper’s much greater thermal conductivity, is a worry. I am not skilled enough to solder them beforehand, except those 10awg leading to the XT90s…

There are multicolored sparklies on the cell after tearing off the strips and cleaning with rubbing alcohol, I wonder if this is the bits of tin and nickel powder that is said to be inside the flux.

I am not sure whether I will use 0,2 copper with 0.1 Nickel plated steel sandwich at 79% power, or order 0.25mm copper and skip the sandwich and use 85% power.

I like the thought of the strength of NPsteel over the flimsy copper, but I also inject silicone under the the folded over tabs , to take stress off the copper and the welds when the battery flexes.

I don’t really need 0.25mm or thicker copper in my builds, but love the idea of minimizing resistance

0.2mm copper just felt too weak on the tear off, but the welds were stuck well. If there is no stress on the welds, then perhaps it is fine?

[Battery_Mooch]

@SternWake

Anybody have an idea to test whether it is corrosive, that doesn’t take 6 months+?

You need moisture and heat 24/7.
Not sure of any decently affordable way to get that, even in a tiny space that could be set up for a few samples.

Nelvick might have the MSDS for the flux. That would list its chemical composition and a bit of poking around could find out if any byproducts of being heated like that are corrosive.

[SternWake]

I’m open to sticking some welded cells in a plastic bag with a black salty rag in a sunny area outside in the insane Florida heat this time of year. The cell can will rust a lot.

I’m still impressed that the nickel sandwich can be eliminated. I was thinking about 0.05mm stainless steel on top of 0.2mm copper to not have to max out the welder, but 0.25mm copper on its own at 85% of its power has my former plan in limbo.

[glyphiks]

@Battery_Mooch

moisture and heat 24/7.

Man lives in Florida, ezpz

[DIY500AMP.COM]

Guys, any supplies you need to experiment with, I’m happy to donate. I really like this thread it’s all about being honest with products, whether they’re good, bad, or ugly, as long as it’s real.

This kind of info helps way more than marketing claims. One of my clients has had great results using 0.1 stainless steel instead of nickel steel, which is corrosive. He says he’s even managed to weld 0.3 copper with it. I believe him, and I’ll be testing his setup myself to see how well it works.

Blazing is very effective, but it’d be nice if we didn’t have to rely on it. Even though it’s supposed to be non-corrosive, it’s still a hassle to get it all over your fingers .

[SternWake]

CN103659053A - Copper welding paste for braze welding and preparation method...

Not sure how close this is to the flux in question.

quote"
The copper welding paste for braze welding comprises 67wt%-92wt% of brazing filler metal, 8wt%-33wt% of pasty fluid and brazing flux of which the mass is 0-5% that of the brazing filler metal, wherein the brazing filler metal comprises Cu and/or one or more types of Cu alloy, the brazing flux comprises any one or more than two components of CaF2, KF, NaF, BaF2, sebacic acid, succinic acid, lauric acid and boric acid, and the pasty fluid comprises a solvent, a thickening agent, a rheological agent, an antifoaming agent and an activating agent. When the copper welding paste prepared through the method is applied before braze welding, the copper welding paste has good thixotropy, collapse resistance and fluidity; after braze welding, a part has high joint strength, a weld joint is plump and free of residues, and the part does not need cleaning; the copper welding paste can be widely applied to welding automobile pipe fittings, copper-based heat dissipation assemblies and stainless steel parts.

[DIY500AMP.COM]

MSDS for the blazing

[glyphiks]

This thread is making my finger feel REALLY heavy over the ‘buy now’ button on the P120D

[DIY500AMP.COM]

I can help to with pricing if you are interested. Send me a PM

[SternWake]

I wonder what differences there might or might not be in stacking 0.15 and 0.10, versus one layer of 0.25.

I have not really played with the pulse interval.
02 to 04ms is the range I have tried.

I wonder what difference it makes. It the longer interval just to heat the cell less?

Does a short interval, that second pulse on hot copper and steel cell can help insure a stronger weld?

I like the strength of nickel plated steel on top of the copper, but the ampacity of NPS is a joke. Rather have more copper.

I’d like to try 0.05mm stainless steel on top of 0.25mm copper and be able to use around 85% of max power.

Is the preheating only about removing oxidation, or will cranking it way up also make for an easier weld on thicker strips?

I can experiment and find out, just wondering the theory behind these features.

[DIY500AMP.COM]

August 21, 2025

[DIY500AMP.COM]

We can use flux, or a thicker piece of nickel or just increase more power to melt even more. Maybe 2 shots? 3 shots? More pre-heat. There are several settings. Remember this beast is up to gear 999.