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My first build after trolling the forum for tips (20s12p p42a ebike battery)

This is actually my 3rd battery build but one was using large li-po pouch cells and the other was too ugly to share on the internet.
I am taking my time and do the best job I can after going through the whole @Skyart battery build thread.
Especially since I have about $1100 in these cells and don’t want to screw them up.
Currently I am just stuck waiting for amazon to deliver more copper sheet so I can continue.

One question I have, the last picture shows the main negative terminal of the battery.
I am not really sure what would be the best way to collect the current from there.
An option I was considering was 5 10ga wires spaced evenly along the width of the tab.
The main wires coming off the positive and the bms will be 6ga going to the ose8 plug and motor controller.


She’s a beast

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Bro you went through my entire battery thread and still didn’t get fishpaper rings? :sweat_smile:

Do you have any pull test pictures of the weld quality? Curious to see how strong the hold it welding through the nickel and copper


Yeah, I may have screwed up there. With the plastic rings on the p42a I didn’t really feel it would be
I used them on my last battery I made from used 18650 cells that I had to rewrap.

And as far as pull test pics I can get some this evening when I get home.
It was tearing both the nickel and copper sheets leaving pieces behind on the cell.


For a second I thought you hadn’t insulated the adjacent parallel groups with fishpaper, but now I see you folded the copper connections and then do fishpaper.

Epic build so far! :smiley:

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Very interesting nickel-copper hybrid system u got going on there. Are you using some very powerful spot welder to get the nickel to weld to the copper like that?


Yeah, it is being built with 5 parallel groups in a row wrapped up into a single piece with fish paper.
4 of those together to get the 20s full pack.

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I was also wondering this

I know Kweld can do it but Idk how it would stay cool long enough to do anything worthwhile

i’d be more nervous about any large potential spark

I am using a Kweld with a large car battery.
It is reporting weld currents right at 1700a so it is getting the job done pretty well.
And the nickel copper sandwich is certainly not my idea.
I have seen it done several places which made me want to give it a shot.
This battery should be able to pump out 300a+ without too much trouble.
So I wanted to have the best series connections I can without going to something thick like a copper braid soldered between groups.

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How many joules?

I have been getting good results at 70j after shortening my leads going between the kweld and car battery as short as possible.
I also removed the xt90 I had which was probably a bottleneck.
That bumped the welding current up from about 1150 to 1650.


Insane. My 1600cca truck battery could maybe do this at room temp.

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Here are the results of a new test weld. @Skyart
70j 1666a
I managed to rip off all the copper and nickel.
But the diameter of the weld in nickel and copper are left behind.


Wow that looks great! :+1::+1:


Dang you used a BMW oem battery lol


Damn I want one of those kwelders. That’s some serious power.

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Holy shit.

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i’ve always wonder how do people charge these car / truck battery :joy:

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I think just a normal trickle car battery charger