Spot Welding Copper Strips to 18650 Battery Cells

[spinningmagnets]

A quick reminder for the casual readers, if the cost of the magnets is a concern, only the negative ends of the cells are extra sensitive to heat. Of course, if you like the magnet method, it works as well on the positive end as it does on the negative.

For the positive end, I think flattening the tip of a solid copper wire and soldering it with a 100W+ unit would work quite well (possibly fuse-wire?). Using a soldering iron with 100W (or more) means that the joint is accomplished in a very rapid manner, so heat does not penetrate deep into the cell.

Of course, for the positive end, spot-welding remains acceptable, since it can take much more heat than the negative end. For copper series bus-strips, the copper/nickel sandwich method is an interesting option.

 

[kdog]

@badazzsteveo
I used a home built transformer based spot welder. Like a mot welder but 2-3x stronger.

 

[spinningmagnets]

From facebook. 20S / 6P, copper/nickel sandwich method.

Molicel 21700 P42A cells, 0.10mm copper sheet, plus 0.15 nickel squares only to facilitate welding.

Edit: kWeld used, setting is 50-Joule

 

[garolittle]

From ES facebook. 20S / 6P, copper sandwich method.

Molicel 21700 P42A cells, 0.10mm copper sheet, plus 0.15 nickel squares only to facilitate welding.

BatteryCopperBus1.png

That is impressive. Kweld used?

 

[spinningmagnets]

Yes, builder just posted that the kWeld joule setting is 50J...

The nickel-plated copper strips from the kWeld supplier seems to need about 80J

 

[serious_sam]

That's a neat looking job.

I'm thinking that nickel strip isn't that expensive that you need to cut it into tiny patches for each cell though. Kinda seems like a waste of extra effort. Just run a strip across multiple cells and be done with it.

Also, I would (did) use nickel plated steel instead of pure nickel. Cheaper. Easier to source. Higher resistance and lower melting point (lower energy required to weld).

 

[garolittle]

Yes, builder just posted that the kWeld joule setting is 50J...

The nickel-plated copper strips from the kWeld supplier seems to need about 80J

Nice! Very impressive. Thanks for posting that.

 

[spinningmagnets]

For the copper/nickel sandwich method, I am certain that nickel-plated steel would work fine. More affordable than pure nickel, too...

 

[ridethelightning]

thanks for putting this here. i saw it on fb and was impressed. seems like the nickle sandwitch technique allows lower welding power to use copper. i will be experimenting with 0.2mm nickel and 1.2 mm copper in this way, ill post results here.

 

[spinningmagnets]

0.15mm___6-mil__34 ga
0.20mm___8-mil__32 ga
0.25mm__10-mil__30 ga

I welcome any experiments. Due to the peak amps of the common cells (30A per cell?), the thicknesses listed above are the copper sheet thicknesses I most want to acquire data on.

As far as the nickel cap, it does not carry series current, and nickel can also be used for the paralleling strips. Since the nickel only needs to facilitate the welding process, there is no need to specify the more expensive thicker 0.20mm nickel strips, although the 0.20 should work well...

0.10 and 0.15 nickel seem to work well as the welding cap. As stated earlier, even the very affordable nickel-plated steel should work well, in any thickness that's available.

 

[serious_sam]

1.2 mm copper

Wow, that's thick. I wouldn't have thought that that's even possible.

 

[garolittle]

1.2 mm copper

Wow, that's thick. I wouldn't have thought that that's even possible.

I am guessing he intended to say .12mm.

 

[serious_sam]

I am guessing he intended to say .12mm.

Possibly. But have you seen his monster mosfet array?! :lol:

 

[garolittle]

I am guessing he intended to say .12mm.

Possibly. But have you seen his monster mosfet array?! :lol:

Ok.... Now I need to see this machine. Someone post a picture so I can engage in "wishful thinking" like I do when I browse the Sunstone Welder website. :lol:

 

[serious_sam]

Ok.... Now I need to see this machine. Someone post a picture so I can engage in "wishful thinking" like I do when I browse the Sunstone Welder website. :lol:

Here is the link. It's only 72 mosfets:
https://endless-sphere.com/forums/viewtopic.php?p=1479497#p1479497

so this is sort of but not really quite an update.
i have now received a prebuilt power switch and pulse control board from a webshop in china, who was making these spotwelders.

 

[ridethelightning]

yeah sorry to get you excited guys i meant 0.12mm copper, but that doesnt mean i wont try thicker stuff aswell. im now trying to figure out which way round to install the tvs protection diode i bought as an extra.

 

[serious_sam]

yeah sorry to get you excited guys i meant 0.12mm copper, but that doesnt mean i wont try thicker stuff aswell. im now trying to figure out which way round to install the tvs protection diode i bought as an extra.

Like this:

From here:
https://endless-sphere.com/forums/viewtopic.php?t=81400&start=550#p1218325

I know this has been explained before (e.g. by Tesseract) but here's my attempt to simplify it a bit for the less technically inclined.

BTW, did you ever get your electric wheelbarrow going ?

 

[ridethelightning]

BTW, did you ever get your electric wheelbarrow going ?

:lol: still in the pipeline! so many things prevented me from following my natural course of electric lunacy this year...i wont even go there. but now its getting colder, much less going on- the perfect conditions for a relapse!
so back to the hubmonster and vtc5A pack(which means getting a new spotwelder sorted) and then once thats going ill be in a better position for doing packs for other projects next in line.

thanks for posting the diagram. i now have the tvs diodes on a lead ready, next to do the schottky ones.

 

[garolittle]

https://endless-sphere.com/forums/viewtopic.php?p=1479497#p1479497

That is AWESOME. Like the "Dodge Viper" of spot welders. LOL

 

[serious_sam]

once thats going ill be in a better position for doing packs for other projects next in line.

Keep us posted!

 

[ridethelightning]

once thats going ill be in a better position for doing packs for other projects next in line.

Keep us posted!

will do. chipping away at this steadily.


T

That is AWESOME. Like the "Dodge Viper" of spot welders. LOL

yes indeed, or maybe a diy waterpipe sawn off shotgun equivalent.

 

[DogDipstick]

My Nickel plated Copper strip compared to 18650ed 0.2mm Nickel plated copper strip. lol.

0.04" x 1.250" ( 1mm x 32mm... )

Muhahahaha. Imma gonna try to tig it.

 

[garolittle]

Not sure if anyone here has tried this but we have been getting very consistent/strong welds using “Nickel Silver”. It does not actually contain silver and is comprised of 65% Copper, 18% Nickel and 17% Zinc. We used a Kweld for the experiments and wanted to share some pictures.

 

[hallkbrdz]

From facebook. 20S / 6P, copper/nickel sandwich method.
Molicel 21700 P42A cells, 0.10mm copper sheet, plus 0.15 nickel squares only to facilitate welding.
Edit: kWeld used, setting is 50-Joule

Interesting. Looking at low resistance spot weldable solutions that can carry around a continuous 17A current per cell, bursting to 44A for ~10 second periods.

 

[serious_sam]

Not sure if anyone here has tried this but we have been getting very consistent/strong welds using “Nickel Silver”. It does not actually contain silver and is comprised of 65% Copper, 18% Nickel and 17% Zinc. We used a Kweld for the experiments and wanted to share some pictures.3AF801B8-7BB5-434A-9D33-46E1A9E0609F.png

Those welds look really nice. I just looked into this material, but it appears to have a significantly higher resistance than all the other alternatives.

COPPER 1.7 x10^-6 Ω.cm
ALUMINIUM 2.6 x10^-6 Ω.cm
ZINC 6 x10^-6 Ω.cm
NICKEL 6.9 x10^-6 Ω.cm
IRON 9.7 x10^-6 Ω.cm
NICKEL-SILVER 28 x10^-6 Ω.cm

https://www.rfcafe.com/references/electrical/resistivity.htm
https://calfinewire.com/datasheets/100146-nickelsilvercda752/

EDIT: added second reference for nickel-silver resistivity