"Copper/nickel sandwich" buses for series connections

[Hummina Shadeeba]

Nickel work hardens easier than brass. It seems irrelevant.

Brass is pretty noble and far away from steel and more causing of galvanic corrosion on the steel cell.

 

[BlueSwordM]

Nickel work hardens easier than brass. It seems irrelevant.

Brass is pretty noble and far away from steel and more causing of galvanic corrosion on the steel cell.

Man, I do so much electrochemical research, and I even didn't of galvanic corrosion on most casing materials

 

[Vincentp]

I have done some pretty extensive testing on the Copper/Nickel sandwich with the Kweld. I have successfully welded up to 0.25mm copper with 0.1mm nickel plated steel. The biggest problem I suffer from is that the copper electrodes have a tendency to stick to the sandwich. My weld energy is 300J at about 1,370 amps. I am going to run some tests with tungsten and molybdenum electrodes, maybe even elkonite if I get desperate($$$).

My question: Is 0.25mm of copper absolutely overkill? The reason I went for such thick copper is that I want the busbars to experience minimal heating while pushing 35 amps per cell with molicel P42A cells. Moreover, I am building packs that are non rectangular, as a result there are situations where the busbar must handle more than 35 amps at certain locations. I did a basic simulation and saw a maximum of 50-60 amps (can't remember exactly) at some busbar locations due to less than ideal current sharing as a result of the pack geometry.

Using thinner copper, say 0.2mm or even 0.15mm copper would be really beneficial, but I am no expert on ampacity and so I have played it safe for the time being.

Following up on this some years later, but thought it would be worthwhile to add that I never got the results I desired from trying to weld 0.25mm copper in combination with 0.1mm nickel plated steel. The welds just weren't quite strong enough.

I ended up settling with 0.2mm copper + 0.1mm nickel plated steel. Weld energy was around 200J but memory is a bit fuzzy now. I always had to warm the welder up with about 10-15 welds so that the resistance could increase sufficiently. Probes needed to be restored regularly. I think I was getting about 200 welds before sanding the probes back to their original geometry. I also always found that the positive or negative probe, cant remember which, would have stronger welds. I would always put one weld on each cell in the p-group, then swap the probes and do the second weld. Probably an unnecessary step, but it felt right to me lol.

I also need to to add that the material was being cut on a cnc and a slot was incorporated…I believe about 20mm in length and 3mm-4mm in width. I believe it was a 1/8th inch bit. So not infinite slot but the next best thing I suppose.

I will be building a new pack trying out the wellgo busbars which I think many are familiar with now.

 

[BlueSwordM]

Following up on this some years later, but thought it would be worthwhile to add that I never got the results I desired from trying to weld 0.25mm copper in combination with 0.1mm nickel plated steel. The welds just weren't quite strong enough.

I ended up settling with 0.2mm copper + 0.1mm nickel plated steel. Weld energy was around 200J but memory is a bit fuzzy now. I always had to warm the welder up with about 10-15 welds so that the resistance could increase sufficiently. Probes needed to be restored regularly. I think I was getting about 200 welds before sanding the probes back to their original geometry. I also always found that the positive or negative probe, cant remember which, would have stronger welds. I would always put one weld on each cell in the p-group, then swap the probes and do the second weld. Probably an unnecessary step, but it felt right to me lol.

I also need to to add that the material was being cut on a cnc and a slot was incorporated…I believe about 20mm in length and 3mm-4mm in width. I believe it was a 1/8th inch bit. So not infinite slot but the next best thing I suppose.

I will be building a new pack trying out the wellgo busbars which I think many are familiar with now.

On the topic of steel, if you peeps can get access to stainless steel strips in place of nickel plated steel, you should try it out.

Stainless steel has even worse electrical conductivity than normal steel, which should help with our method of copper-sandwhich welding. Honestly though, our copper-metal sandwiches might as well be copper-clad welding sandwiches

 

[Zambam]

Following up on this some years later, but thought it would be worthwhile to add that I never got the results I desired from trying to weld 0.25mm copper in combination with 0.1mm nickel plated steel. The welds just weren't quite strong enough.

I ended up settling with 0.2mm copper + 0.1mm nickel plated steel. Weld energy was around 200J but memory is a bit fuzzy now. I always had to warm the welder up with about 10-15 welds so that the resistance could increase sufficiently. Probes needed to be restored regularly. I think I was getting about 200 welds before sanding the probes back to their original geometry. I also always found that the positive or negative probe, cant remember which, would have stronger welds. I would always put one weld on each cell in the p-group, then swap the probes and do the second weld. Probably an unnecessary step, but it felt right to me lol.

I also need to to add that the material was being cut on a cnc and a slot was incorporated…I believe about 20mm in length and 3mm-4mm in width. I believe it was a 1/8th inch bit. So not infinite slot but the next best thing I suppose.

I will be building a new pack trying out the wellgo busbars which I think many are familiar with now.

Have you seen this video by ZEUS-FL Tabless design cylindrical cells tests ? Maybe worthwhile doing some experiments with the copper flux? If you do, please share results.