Spot Welding Copper Strips to 18650 Battery Cells

[SlowCo]

Like this I mean:




That way you would need (much?) less current to weld and might be able to spot weld copper strip using the simple spot welders if you insert tungsten tips in the electrodes.

 

[Hillhater]

Whilst i agree it does seem logical to use the probes that way, and i have tried to figure out why we dont,...i also find it hard to believe that the big players making commercial packs... (Panasonic, Sony, LG, etc etc) .. have not already explored all these possibilities and settled on the optimum method which we see in use currently.
But worth a try for someone with a welder and spare time !

 

[kdog]

That technique can work well- but it is less consistent bc the electrodes are on different surfaces... and once you've popped the nickel on, you can't access the cell. And you have to do twice as many welds and it heats the can more. That's what slotting is for.
K

 

[Skrzypas]

That technique can work well- but it is less consistent bc the electrodes are on different surfaces... and once you've popped the nickel on, you can't access the cell. And you have to do twice as many welds and it heats the can more. That's what slotting is for.
K

I tried this way on mine MOT half year ago and I couldn't weld 0.1 mm copper. But I experimentally checked, that definitely you need to set shorter pulse time when putting one electrode on the can. With the standard pulse I use for nickel, in case of one electrode on the can I made a hole the "test can".

 

[Matador]

https://www.youtube.com/watch?v=OrjLdLXSDAA

Seems like it takes a LOT of energy so spotweld copper, but I guess not impossible. See vid !

 

[cut cat]

'
Exciting update. The following post by ridethelightning and kdog has confirmed the use of a tungsten probe to aid in spot welding copper.

....the key to making it a smooth job i think is a tungsten tipped electrode. this will not melt like a copper one or stick to the tab. it will also create the resistence needed to create the heat for the weld, at the tip, similar to the effect kdog saw when only using light presseure with his copper electrodes....though...kdog knows all of this, hell, i banged on about it multiple times in a fever of excitement from seeing the copper tab actually welded properly with his MOT welder...

https://endless-sphere.com/forums/v...5&hilit=ultimate+repository&start=75#p1104439

From what I have read on welding copper is copper fumes are very toxic. So you need to do this with a fume hood

For TIG welding copper, the following settings are recommended: DC straight polarity, 2% thoriated tungsten and helium/argon shielding gas.

Here is a link to tungsten electrodes that are 3/32" diameter. They are easy to to cut using a metal cutting grinding blade and easy to sharpen to a point with a belt sander. Just keep the grind marks parallel to the electrode. The tip shape is very important. Based on the images below, I think a 90° angle with a 0.02" diameter blunt end would be best.

https://www.amazon.com/Welding-Tungsten-Electrodes-Thoriated-10-Pack/dp/B013KZNLGG

.

You will find grinding Thoriated Tungsten is very toxic.

If purchasing Tig tungsten eletordes to make your own, Green is pure Tungsten where other colours have other elements. It might be a good idea to find out what tungsten electrode colour / type Sunstone use for copper.

 

[mkp007]

You will find grinding Thoriated Tungsten is very toxic. If purchasing Tig tungsten eletordes to make your own, Green is pure Tungsten where other colours have other elements. It might be a good idea to find out what tungsten electrode colour / type Sunstone use for copper.

Good call on the toxicity. Use a good dust mask. Put a vacuum next to the grinder to collect as much as possible. Prevent dust from becoming airborne. Clean up any dust and dispose.

I researched TIG welding copper and the one source I found said the 2% thoriated tungsten rods (RED) were good.

Here is another source for tungsten selection: http://weldingdesign.com/consumables/selecting-and-preparing-tungsten-electrodes-tig-welding

What is the output current for spot welding, AC or DC? I'm guessing AC as most MOT spot welders are simply a transformer stepping down the voltage and upping the current. But what about the Sunkko 709A spot welder? Reason I ask is that may play a part in selecting the type of electrode.

 

[kdog]

I had zero success with tungsten electrodes. I use pure copper electrodes. I think the main problem is that my welder only puts out about 6v. (RTL is using a DN10 so not sure what output V is on that), I think the increased R of tungsten restricted the current compared the copper electrodes. The tungsten welded itself to the work piece so strongly it was totally destructive trying to get it off! The DN 10 using quite a bit mor power seemed to make the tips glow red hot for a second possibly freeing the electrode as it welded.
I just use some thick solid copper wire for my electrodes. Copper welds everything :wink: although it is a bit soft. I welds copper well, I suspect bc the electrode/ copper interface resistance is still lower than the copper/ nickel interface.
K

 

[Matador]

From the specs of a spot welder that can do Copper (Orion EV 250i : see specifications here for the enrergy specs http://www.nordsondima.com/sites/default/files/divisions/products/downloads/datasheet_dima_welding_-_orion_pulse_250i_ev_lr.pdf)

I see the welder has an energy rating of 0.5 to 250 W.s (watts x seconds, which in other words is 0.5 to 250 Joules).

My thought is if I can find a big enough capacitor, I could reach these energies.

For example, with this enormous capacitor : http://www.ebay.ca/itm/181989950926?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT


From a theoretical point : E = 1/2 C x V^2
That capacitor is 80V and 0.22 Farads

So E = 1/2 x 0.22 x (80)^2
E = 1/2 x 0.22 x 6400
E = 704 Joules (or 704 W.s) sooo much higher thant those 12 volts audio 1.5 F capacitors (108 Joules)

To make it 250 W.s, just set charge voltage at 47.67 volts
Yet there's headroom to go up to 700 Ws

This other one capacitor : 100V, 0.15Farads, for a total of 750Joules (PS: getting shock with these, I'd be afraid to go into arythmia LOL)
http://www.ebay.ca/itm/1PCS-HITACHI-100V-150000UF-Electric-car-acceleration-capacitor-90X170mm-E381-YX/172068614912?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D39923%26meid%3Df3a08feba40745e3ac7607b290fac782%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D172069439462

Could this work ???

 

[Matador]

I guess the price is too good to be true (most probably fake capacitors)...
http://sound.whsites.net/fake/hitachi-caps.htm

 

[litespeed]

My capacitor discharge welder is 800 watt seconds using 3- 1 farrad and is voltage adjustable to 23.2 volts.

https://endless-sphere.com/forums/viewtopic.php?f=1&t=68521

I'm hoping it has the balls to get this copper spot welding done.

The capacitors I'm using I tested and they are 25 volt & true 1 farrad each.....about 3.1 something total. There used to be a guy on eBay that sold these and has since sold out. They were about $200 for all three about 2nyears ago.

Tom

 

[Matador]

My capacitor discharge welder is 800 watt seconds using 3- 1 farrad and is voltage adjustable to 23.2 volts.

https://endless-sphere.com/forums/viewtopic.php?f=1&t=68521

I'm hoping it has the balls to get this copper spot welding done.

The capacitors I'm using I tested and they are 25 volt & true 1 farrad each.....about 3.1 something total. There used to be a guy on eBay that sold these and has since sold out. They were about $200 for all three about 2nyears ago.

Tom

Wow, awesome welder ! At 800 Ws, you should have more than enough energy for copper, and finding good tungsten electrodes is probably equally important.

If the Orion EV 250i can do as much as 20 mils (0.51 mm) thick copper and is only 250 Ws, i have high hopes that your 800 Ws machine will be more than enough ! You'll probably have to adjust voltage not to burn a hole through the cell

 

[litespeed]

Finally got around to ordering the tungsten electrodes that Sunstone recommended for copper,

http://sunstonewelders.com/product/resistance-tungsten/?attribute_tungsten=EL125TUNG

I'll let you know how it works out.

Tom

 

[mkp007]

Finally got around to ordering the tungsten electrodes that Sunstone recommended for copper, http://sunstonewelders.com/product/resistance-tungsten/?attribute_tungsten=EL125TUNG
I'll let you know how it works out. Tom

Interesting shape for the electrode. Can you confirm with them the optimum shape of the electrode tip?

Also, that says pure Tungsten. Can you ask them if they have tried 2% Thoriated tungsten and why they use one vs the other?

Here is the link on Amazon for the 2% thoriated tungsten electrodes that I bought for TIG welding aluminum. I would think that welding aluminum and copper is similar. https://www.amazon.com/gp/product/B013KZNLGG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

And while we're at it, can you ask about DC vs AC current? Most Sunstone welding copper are DC I believe. If so, this would favor capacitor over MOT type welders . If you notice in most Sunstone videos, there is a pause when the electrodes make contact with the strips and when it fires the discharge. Either they are pre-heating the metal or it is charging the capacitors.

Check out Figure 3 of this document. It talks about the various spot welding configurations that have been mentioned a few times here.
http://www.powerstream.com/ss/PSSunstoneDPWelderIP.pdf

 

[litespeed]

Finally got the tungsten probes from Sunstone Engineering late last night. Been to busy at work lately to source some copper so I may just try my local well stocked hobby shop to see what they have tomorrow.

It's crazy how heavy these are for being so small.

Tom

 

[spinningmagnets]

Welding copper paralleling strips onto the nickel-plated 18650 cell ends remains to be dialed-in, but...I am now convinced that the absolute best way to connect the thick copper series-flat bars between P-groups is the cheap "caveman" high-current spot welder made from an easily modified Microwave Oven Transformer (MOT).

https://endless-sphere.com/forums/viewtopic.php?f=14&t=85023&p=1243616#p1243616

If the localized heat proves to still be a problem in some way, then the series connector bars and the thinner paralleling strips can be spot-welded together in a positioning jig before they are spot-welded onto the 18650's (and that last connection to the cell-ends would likely be a different method).

Notice the bare fingers, because the high-current weld happens so quickly.



I know I need to narrow down the thickness of the parallel strips, and also the series flat bars first, along with clarifying the amps i will be running (600A? 800A?), but....which tungsten rods are the best to start with? Sunstone has them as small as 1.0mm diameter, 1/8th inch diameter and 3/16ths diameter?...

http://sunstonewelders.com/products/accessories/electrodes/

 

[kdog]

I have just finished spotwelding up a little 2s2p pack for a mates light. I did it in .2mm brass to see how it would go (Plain old yellow brass (c26000) iacs 27%). It welded easily, not quite as easy as nickel but close. I'm practicing for a large upcoming build (21s10p of 30q's) to see if brass will substitute for nickel. I'm not set on anything yet just practicing. Any combo of nickel, brass, copper will weld together so that's good.
The only real advantage over nickel is cost- conductivity is marginally better, but It's about 1/2-1/3 of nickel and readily available in 100-300mm wide.
I'm yet to find anywhere to supply other specialty copper alloys...
SM
Copper welds to nickel very well, in fact I prefer putting down nickel first to give the can a bit more protection from fickle coppers' inevitable blowouts.
I think you'll find pre spotwelding difficult. The heat is a non-issue if you are doing it right. The can is barely warm as quick as I can touch it.
I hope your not planning anything like the welding in your picture!? Ha maybe you will need to pre spot weld!!
K

 

[spinningmagnets]

Micah Toll, and a cell supplier called supower111 were both selling paralleled sub-packs with conventional spot-welded nickel strips. I had considered buying these and then making the series connections myself. Once I came to the conclusion that the series connections should absolutely be thick copper, its a short jump to making the thinner parallel strips copper too.

Brass sounds like a viable option. If conductivity of copper is 100, the previously posted chart shows nickel is 22 and brass is 28...so...23% more conductive than nickel, much more affordable to buy (so we can cheaply make it extra thick), but still resistive enough that it would weld easier than pure copper. Brass for the parallel strips is a brilliant suggestion.

Looking at the chart in the link below, aluminum is cheap, available, and very conductive. I'd say copper, aluminum, nickel, and brass are the only options worth considering. For the parallel strips, it is the resistance of nickel that makes welding it onto the cell tips easy with a conventional spot-welder. But when desiring high amps, the resistance of nickel is bad...and making it thicker is very expensive.

I still think we should finish investigating the welding of copper ribbon onto the nickel-plated 18650 cell ends, but...brass would require much less heat to do that, conductivity is 23% better (so voltage drop would be less at the same thickness), but...thicker strips of brass are cheap. Its softer than nickel, harder than copper, so it can also be cut at home (instead of waiting for laser-cutting).

https://www.bluesea.com/resources/108

0.20mm thick nickel is roughly 0.008-inches (26-ga sheetmetal). Thinnest brass sheet I found online just now is 0.016-inch, and $10 for 12 X 12 inches. The button on the 18650 positive cathode is around 8mm across (a hair under 3/8ths inch). If we sheared off the strips instead of cut with a saw, 12-inches wide provides roughly 28 strips at 12 inches long, 6P requires strips 120mm long (5-inches?) so each 12-inch long X 8mm strip per P-string (up to 8P). 28 strips = 2 X 14S

The 0.40mm thick brass sheet required to make the parallel connections for an 8P / 14S pack would be about $5

 

[litespeed]

Pretty good read for resistance welding,

http://www.amadamiyachi.com/servlet/servlet.FileDownload?retURL=%2Fapex%2Feducationalresources_articles&file=01530000000Jybm

Tom

 

[spinningmagnets]

I have started a thread to discuss using BRASS as a spot-welded material, to make the PARALLEL connections in the pack.

"Brass for spot-welding 18650 parallel cell groups?"
https://endless-sphere.com/forums/viewtopic.php?f=14&t=85059

If this thread can find a method to easily spot-weld copper parallel strips to the nickel-plated 18650 cell ends, that would be a better solution.

 

[litespeed]

Well I'm disappointed at best right now. I finally got a few minutes to play with the new tungsten electrodes I received from Sunstone. I went up to the hobby shop looking for some copper foil and the thinnest I could find was .016 or .406 mm for our metric brothers out there. I couldn't get it to stick to the cell to save my life. From about 20volts on up I just blew 2 holes through the copper literally vaporizing the metal. I know it was really thick but I was hoping my CD welder had enough horsepower to get it done or at least get a little to stick to the cell.

I also found some brass shim stock that I tried as well. I was looking for .2 mm and all I could find was .127 mm which is kind of on the thin side. I installed the tungsten electrodes since I was trying the copper and now know that they are not the right choice for the brass. All I kept doing was blowing holes through the metal. I'll try again with the glidcop electrodes that work perfect on nickel since these two metals have pretty close to the same resistance.

See the pictures,

Tom

 

[kdog]

.4mm cu is pretty thick! Not surprised it won't weld... Hammer it out a bit if you can't wait! Have you got some pure copper electrodes for reference? I found factors other than power were really important for copper like pressure, surface prep etc.
keep trying!

 

[litespeed]

So I gave it another try and it appears I need longer weld times. I did hammer the copper slightly maybe thinned it another .002 thousands or so to maybe around .35 mm. I put the 1 pulse at .5 and my second at 18 and it stuck......or at least one side did. Then I went to 20 on the second pulse at 21 volts and it blew a hole in the copper and the cell. All this blowing holes is also eating the tungsten electrodes pretty fast as well. I think I've already lost 1/8" of each on 15 tries. The left side blows more but I forget right now if that's the positive or negative side. Just need to get some 32 gauge so I can really get some testing in.

Getting closer.

Tom

 

[litespeed]

I was thrilled just to get some progress. At first I was shooting for the most power and the shortest duration time since copper sucks the heat out. I've found out that to high of voltage causes blow outs so now I need to keep the voltage lower and experiment with longer pulses. Possibly try different probe pressures as well. Right now I'm pushing as hard as I can to try and get as much energy to the copper and cell.

It's happened enough that you'd think I'd be used to it but when this thing blows a hole in copper or nickel if freaks me the f@#k out!!! Never ready for it even though I think I am. On The last one since it also blew a hole in the cell casing seemed to be the loudest/brightest one yet.

Tom

 

[spinningmagnets]

Here's a video from sunstone:

https://www.youtube.com/watch?v=OrjLdLXSDAA

[youtube]OrjLdLXSDAA[/youtube]

"...The CD1000DP was set at 310ws energy to weld the .005" copper tab to itself, and at 510ws energy to weld .005" copper tab to .010" copper tab...tungsten electrodes"

The welders name means "Capacitive Discharge, 1000W, Dual Pulse, Model-2"