Nickel Strip -- looking for reliable source

[jas67]

I just ordered 160 high-current 21700 cells (Samsung 40T) to build a battery for my electric-converted Vespa.
It already has one 20s8p battery built with the same cells, I'm building a second one for additional range, and to reduce heating of the battery during sustained high-power usage (70-100A @ 72V).

This is my first battery pack build. I've already ordered a Sunkko 709A spot welder. I've not yet gotten cell holders and nickel strip. I'd like to do a honey-comb configuration to keep the size down. As I'm spreading the load across two of these battery packs, cooling shouldn't be a problem. The existing pack is honeycomb configuration.

I'm a bit apprehensive about buying the nickel strip from "any old vendor" on Amazon for fear of getting nickel plated steel advertised as pure nickel.

I'd like to do 10mm X .2mm for the best current capacity. I'd like to be able to run the scooter off one pack at a time if needed, thought will almost aways run both. When running one, continuous current climbing hills can be as high as 120-140A for the pack, or, 12-14A per cell. More commonly the draw is more like 50-70A.

When running both packs, even climbing hills, I'll be at about 7A per cell max, well within the ampacity of 10x.2mm nickel.

So, what is a reliable vendor to get 10x.2mm nickel strip from?

Is it available in wider widths, 12mm, or 15mm? That'd be better yet!

Also has anyone here welded .2mm with the 709A? Does it do well. From what I'm reading, I need to use the fixed-mount electrodes to weld .2mm strip, that the hand-held "pen" is only good for .15mm.

 

[jas67]

I got the cells from:
https://www.bulkbattery.com/

They were listed as "new" cells, so, they should be A-grade, no?

I wanted high-discharge rate cells for minimal internal resisitance.
The motor on this scooter can easily draw 200A, though, I have the current limit set at 120A for the moment with the single 20s8p pack in it.

I may turn it back up to 200A once I have both packs in parallel.

Once both packs are installed, I'll usually (as in almost always) aim to keep it between 20 and 80%, which is hard to do with the current range of about 28-30 miles. Range with both packs will be 60+ (yes, greater than double due to less losses due to internal
and interconnect resistance).

The BMS is Daly 20s 150A.

Yes, I will share the pack build.

 

[spinningmagnets]

Please read the "copper nickel sandwich" thread. For the high amps of a scooter, I think it would benefit you.

 

[tomjasz]

Ann Power Lithium battery
AliExpress
5 years issue free

 

[jas67]

Please read the "copper nickel sandwich" thread. For the high amps of a scooter, I think it would benefit you.

I did start reading that one after making this post. Thank you -- lots of good info there.
I've already ordered some copper foil (.08mm and .15mm) and some .1mm nickel to try.

 

[jas67]

I sourced some .08mm and some .15mm copper foil, as well as .1mm nickel.
I also sourced some empty practice cells.

I have a Sunkko 709A welder.

I've never spot-welded this kind of stuff before. I was able to get nice solid welds with the .1mm nickel by itself.
Trying the nickel-copper sandwich, I got it stick, but could be pulled off with relative ease. I tried slitting the copper and then made sure each electrode was on a different side of the slit. That helped. What helped even more was cutting a slot to be sure the two different halves of the copper did not touch.

I'm going to be building a 160-cell battery pack. I think that labor-wise, it will be MUCH more involved to do the copper sandwich for the series connections, as I need to slot the copper to get a good weld.

As this is going into a vehicle, and not a stationary project, I'm concerned about the durability of the copper welds with vibration.

I've ordered some 80mm wide .1mm nickel sheet. My pack is 20s8p. My plan is to cut pieces of this nickel sheet to have one solid piece of nickel for my parallel and series connections (two rows of 8 cells all welded to the same sheet) vs. separate strips for parallel and series connections.

This should give me roughly 170mm wide series connections for the whole pack (passing the entire 8p current), or the equivalent of roughly 20mm wide series connections between rows of parallel cells. This will be the equivalent of .2 x 10mm strips.

I am also going to source some .2mm nickel strip to see how well this welder does with it. I'm looking for, but, have not yet found .15mm or .2mm nickel sheet. If I can find it in 40mm or wider widths, I can do what I propose above with thicker nickel for even lower losses in the series connections.

For the B+ and B- connections, I've sourced some 15mm x 3mm copper bar, which I will attach to the last parallel cells on each end using the nickel sheet. I'm not yet sure if I'll just use screws and washers to connect the copper to the nickel, try to weld, or do both. I'll then drill and tap some screw holes in the copper bar to attach the 4 AWG welding cable that will connect the battery to the scooter via an Anderson SB175 conector.

 

[cliffamatee]

I know sunkco sells what they list as pure nickel. You would think it would be pure seeing they sell the most common spot welder.not sure how sunko is spelled.. If you look at the welder itself it looks like sunkco ..I have not tried the nickel but perhaps someone could share their experience with this nickel

 

[tom355]

The following Aliexpress Shop has pure Nickel. I bought there. It`s not rusting in saltwater.
And there are no sparks when you Dremel it.

https://de.aliexpress.com/store/718097?spm=a2g0o.detail.1000007.1.37f4470cO8ohkr

 

[jas67]

I have ordered some 30mm wide 0.2mm strip from seller "hirewire" on eBay.
I'll post my thoughts on it, and how well the 709A handles it after I get it.