"Copper/nickel sandwich" buses for series connections

[Cowardlyduck]

Wow! What an awesome response. Thanks heaps guy's, there's some very sensible idea's there!

Cheers

[spinningmagnets]

"Michael Le Van" on Facebook "18650 Battery Packs For Beginners"
0.10mm copper, 0.10 nickel

A

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[ridethelightning]

Here is my 22S14P VTC6 HG2 hybrid battery. I couldn't afford the extra VTC6 needed so I went with HG2.

There is a total of 470g of copper over the full battery.

I used 6mm squares of 0.1mm nickel and welded as close as I could to the corners to make the most of the 1750A my welding battery can supply. I learned that decreasing the current by 30% required almost 100% more weld time on my particular setup. Much past 30m/s is not worth it imo. I don't like to profile my tips too sharp due to the erosion so I will be making an adjustable current sandwich welder that will do 2500A for the more stubborn materials. I also want to experiment with dual pulses as this might be able to temporarily increase the resistance of the copper.

IMG_4592 copy.JPG
IMG_4588 copy.JPG

beautifully made pack. i made one similar then another one after that. i realised you dont need to do the zigzag pattern! it can be all done with straight diagonal shapes except the groups at the ends of the pack, still need some curvy tailoring. much quicker to cut out and weld that way.

[Darren2018]

Here is my 22S14P VTC6 HG2 hybrid battery. I couldn't afford the extra VTC6 needed so I went with HG2.

There is a total of 470g of copper over the full battery.

I used 6mm squares of 0.1mm nickel and welded as close as I could to the corners to make the most of the 1750A my welding battery can supply. I learned that decreasing the current by 30% required almost 100% more weld time on my particular setup. Much past 30m/s is not worth it imo. I don't like to profile my tips too sharp due to the erosion so I will be making an adjustable current sandwich welder that will do 2500A for the more stubborn materials. I also want to experiment with dual pulses as this might be able to temporarily increase the resistance of the copper.

IMG_4592 copy.JPG
IMG_4588 copy.JPG

beautifully made pack. i made one similar then another one after that. i realised you dont need to do the zigzag pattern! it can be all done with straight diagonal shapes except the groups at the ends of the pack, still need some curvy tailoring. much quicker to cut out and weld that way.

Thank you. I used both yours and serious sams builds as references. You both produce nice work.

What do you mean about the zigzag pattern?

[ridethelightning]

wish i had pics but they are on my old laptop.
basically imagine the p groups look like sections in a box cutter blade, except the ends.

[ridethelightning]

has anyone got a good source tried and tested for t2 or c110 copper alloy in 0.2mm?

[spinningmagnets]

From "Lode Crommen" on facebook "18650 packs for beginners"

14S / 6P
0.10mm copper
0.15mm nickel
Kweld 120J

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[john61ct]

Any examples of a low-tek construction technique to fab a robust aluminum enclosure for that?

I'm thinking a sliding front and back

with screening behind to allow for ventilation as needed

but pretty splash-proof when closed up

[spinningmagnets]

From Ian M Molina, Facebook, "18650 battery pack for beginners"

kWeld, 0.15mm nickel plated steel caps, 0.20mm copper foil

20S / 7P, 100A continuous, peak 200A

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[atckirk]

Once I had the copper bus plates cut, I just had to stay fairly close the "slit" cutout with the weld probes, as I knew that cutout was dead center to the physical cell below it.

A couple questions, how do you setup a grid in inkscape on a diagonal? And when you are cutting the copper on the CNC how do you hold it down, tape the edges, spray glue? I'm fairly inexperienced at inkscape and CNC both so I'm not clear on those.

Thanks! Kirk.

[spinningmagnets]

Nothing wrong with using CNC or laser-cut/water-jet, but...the 0.10mm and 0.15mm copper sheet that seems to work well is easily cut by stout scissors.

[ZiaMag]

File -> Document Properties -> Grids

Create a new axonometric grid. Inkscape defaults to isometric (120° angles) but you're not working in 3D space, just using the grid intersections as object center snapping points. Adjust major and minor line distances and reference the intersections as needed with the cells and space appropriately. This part took me a while. I did initially attempt to create a parametric openscad file with plans to publish it to thingiverse, but Inkscape proved to be easy quicker and more hands-on, also openscad is damn clunky.

Nothing wrong with using CNC or laser-cut/water-jet, but...the 0.10mm and 0.15mm copper sheet that seems to work well is easily cut by stout scissors.

In reality, cutting the copper can be done with really lame scissors, even just an exacto blade. Why I used the CNC? Because A - the slits were the reference to the spot weld area. Kinda flying blind without the slit, so accuracy in that regard just made everything easier when it came down to positioning the weld probes.

And B - Logic is scarce in a garage machine shop. One could certainly argue the entire affair is preposterous... The easy part is using the overkill CNC at every opportunity. Getting it ordered, in the house, built up, and doing so with the wife present is the issue... there are no tool path techniques or CAM strategies on your side for that one. The CNC also made very easy, very very quick work of the needed shapes.

I used the painters tape and super glue method to hold the copper in place. A steep V-Bit with just enough depth of cut, one pass. High speed and feed rate. Dollar tree foam-board as the backing under the copper sheet.

[atckirk]

File -> Document Properties -> Grids

Create a new axonometric grid. Inkscape defaults to isometric (120° angles) but you're not working in 3D space, just using the grid intersections as object center snapping points. Adjust major and minor line distances and reference the intersections as needed with the cells and space appropriately. This part took me a while. I did initially attempt to create a parametric openscad file with plans to publish it to thingiverse, but Inkscape proved to be easy quicker and more hands-on, also openscad is damn clunky.

Nothing wrong with using CNC or laser-cut/water-jet, but...the 0.10mm and 0.15mm copper sheet that seems to work well is easily cut by stout scissors.

In reality, cutting the copper can be done with really lame scissors, even just an exacto blade. Why I used the CNC? Because A - the slits were the reference to the spot weld area. Kinda flying blind without the slit, so accuracy in that regard just made everything easier when it came down to positioning the weld probes.

And B - Logic is scarce in a garage machine shop. One could certainly argue the entire affair is preposterous... The easy part is using the overkill CNC at every opportunity. Getting it ordered, in the house, built up, and doing so with the wife present is the issue... there are no tool path techniques or CAM strategies on your side for that one. The CNC also made very easy, very very quick work of the needed shapes.

I used the painters tape and super glue method to hold the copper in place. A steep V-Bit with just enough depth of cut, one pass. High speed and feed rate. Dollar tree foam-board as the backing under the copper sheet.

Thanks for the info! That will be helpful when I start to build my packs

Kirk.

[spinningmagnets]

From "Ian M Molina"
Facebook "18650 Battery Builders"
84V, kWeld
0.15mm copper

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[john61ct]

Gorgeous!

So at the top are those just spare cells?

[spinningmagnets]

Buses not complete at the time of that pic. The two groups at the top are the end-collector cells for the positive and negative cables to the controller.

Here's the same pack, a little farther along. If you look close, you can see the top right bus has the edge bent over the top, and there is a horizontal copper plate that will somehow have the positive cable for the whole pack connected to it.

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[Tomblarom]

I finished my "battleship" pack and think it turned out incredible. I used two row "H-style" nickel strips, which I split in half.

Cells: Samsung 50G 21700 5Ah (real 4,8Ah)
Pack: 14S5P (70 Cells)
BMS: LLT smartBMS (xiaoxiang) 60A
Capacity: 24Ah
Cellholders: custom 3D-printed

Welder: kWeld @ 110J
Battery: generic car battery 59533 (740A 95Ah)
Connections: 0.15mm Nickel + 0.15mm Copper

Also posted this on Facebook: https://www.facebook.com/groups/2021407 ... 198868078/

[Frank]

Looks great! Did you use *real* nickel strips, or nickel-plated steel?

[john61ct]

Higher resistance for the nickel strip is a good thing right? Only used to heat-adhere the copper

which is what's carrying the power flow

[Frank]

I've used the sandwich technique with what I thought was real nickel but was actually nickel-plated steel. It does heat up nicely to make the weld. I *think* this works better than pure nickel but am always on the lookout for new information.

[spinningmagnets]

All previous evidence points to steel caps being the best material. Having them nickel-plated prevents corrosion in the future.

Nickel-plated steel for the win...

Steel has four times the resistance compared to nickel. This means that the kWeld watts are converted into enough heat to make a good weld-bead at a lower setting. Then, the kWeld will run cooler.

Another potential benefit is that since the Joules of power of the kWeld has a hard ceiling, using steel caps means that the copper can be thicker.

More experiments are needed, but...0.15 copper appears to be reliably welded when all of the components are optimized.

That thickness of copper will support the highest-amp 21700 cell.

[Tomblarom]

Did you use *real* nickel strips, or nickel-plated steel?

I highly assume it was plated nickel. It welded like a charm. Also I never tested the pureness using the saltwater test.

Today I made this addition, to avoid a clunky cable on the side and save space. This solution seemed to me the best for this kind of cases. I used a double layer of 0.15mm copper, soldered the top to the BMS and welded the lower end to the battery minus.

[NexusG]

All previous evidence points to steel caps being the best material. Having them nickel-plated prevents corrosion in the future.

Nickel-plated steel for the win...

Steel has four times the resistance compared to nickel. This means that the kWeld watts are converted into enough heat to make a good weld-bead at a lower setting. Then, the kWeld will run cooler.

Another potential benefit is that since the Joules of power of the kWeld has a hard ceiling, using steel caps means that the copper can be thicker.

More experiments are needed, but...0.15 copper appears to be reliably welded when all of the components are optimized.

That thickness of copper will support the highest-amp 21700 cell.

It will be interesting to know if 0.15mm copper is enough to support the future 4680 cells... probably not !

Maybe we will need 0.20mm, 0.25mm or even higher thickness copper and that's not possible to solder it reliably with the kWeld, even with nickel plated steel caps, slots, etc.

We will probably need to have a more powerful version of the kWeld

[spinningmagnets]

The kWeld can make the "tab" connection to the outside of the 4680 cell, though I doubt we will get our hands on them for a decade or more. When they become available from a Tesla car crash, they will be expensive, so the desire to use them would be more for "bragging rights".

Tesla uses a thick aluminum bus-plate, with a fuse-wire connecting the cell-end to the plate. The pic below was for a similar high amp DIY motorcycle, and it uses a short nickel tab to connect the cell to the thick copper bus-plate. It would have benefitted from the tab using a copper/nickel sandwich, but it was from quite a while ago. Also, a 4680 cell can use a 40mm wide copper/nickel tab.

A short copper tab (with nickel cap) that is 40mm wide x 0.15mm thick = 6.0mm sq. This cross section of square-wire would be equal to 10-gauge/10-AWG "round wire", which is 50% more copper than the 12-ga wire that is common around here. The 0.15 copper sheet can be connected to the thick copper bus-plate by a brute-force 2000A spot-welder. https://www.electricbike.com/resistance-soldering-unit/

The shape of the thick copper bus-plate was laser-cut, and can also be cut with a "water-jet".

[zzoing]

Wow that's a very good idea. Perhaps someone can get a machine that rolls a copper wire and a nickel strip through some compressor rollers which weld them using spot welds or flux, that would be an easy to weld nickel strip with a copper wire running on the side and it would be kinda kool!