First try at welding 21700s

So keep em on, mark the dot, take em off?:eyes:

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take em off. @glyphiks makes a good point. you’d rather have that area to spread your spot welds off center. welding on the bottom center risks messing with the internal attachment of the anode to the can.

also you’d be spot welding into the dip, which can’t help things.


@Battery_Mooch @glyphiks howd i do on my pull test?! :grin: Holes all the way through and they stuck amazingly to the cells!! (Using a malectrics spot welder now on 25ms with 12% of pulse time)

That’s less than ideal.

Search the battery builders thread for ‘pull test’ should get you some useful information

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I am going to steal a paragraph from the thread linked below, written by someone with far more experience than myself:

“None of these welds are sufficient, not even close really. The tiny dots left behind are only slightly better than the nothingness. You should have to tear the nickel off destroying the strip in a way that looks like wolverine removed it, they should never pop off by prying”


Any stronger and it destroys the strip.

Idk what to do then. Any stronger and it destroys the strips. It takes a considerable amount of force to tear these off

And even after checking the builders club even skyart agreed someone who did welds just like mine are solid

This is 0.1 copper and 0.1 nickel plated steel sandwich. The top weld is a 60 ms pulse on a welder nowhere near malectric quality, the bottom is 80ms.

The strip should be destroyed when removed. A tiny torn dot at each weld is not satisfactory. Do one pair of welds like you show, then wiggle and lightly torque the strip 10 times, I bet it falls off.

You might need to blunt the edges of your probes, no sharp cylindrical corners. and Not too much downward pressure.



I can hold the whole p group and jiggle it without a weld coming loose.

I think we should rewind to Glyphiks ‘far from ideal’ comment.

Only few have more esk8 battery building experience.

I gotta bow out, as I know nothing.

Best of luck

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U asked for advice. You were given it, u ignored it. :man_shrugging:t2:


This is an excellent example of what a pull test should look like.

The material should hold on so well that the only way it comes off is irregular tearing of the material.

The photo that @Rhythm has presented might indicate that there has been too much energy put into the weld and the area surrounding the weld has been weakened, allowing it to shear off in a perfect spot like that.

That has been my experience anyway, i would not be happy with a pull test like that.


I completely agree.
While a perfect dot of metal might indicate that the weld was solid it is also the symptom of an over-power weld that blew through the metal in a circle, leaving that nice dot.

It taking a lot of force to remove the nickel is a good sign but a better sign is a big tear of nickel still stuck to the top of the cell. I don’t have any recommendations for achieving this though, just that for me a “best practice” is the torn nickel.

Hmm…I’m wondering if the inexpensive AC IR meters like the YR-1030 and YR-1035 can detect a perfect/not-so-great weld. I’m sure my micro-ohmmeter can but they cost a fortune and there’s no way any builders should have to buy one.

Those two inexpensive meters measure down to fraction of a mOhm might just be able to see the difference between different strength welds. I’ll try a couple of tests…LOL, in my copious free time.

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What makes no sense to me is im told look in battery builders club to see examples. I do exactly that and see people who have welds just like mine and are told theyre fine. And if i go any weaker on the spot welder it wont stick strong. If i go higher it destroys the strip. I even used the settengs that were recommended by malectrics. So idk what im supposed to do at this point. Just cause it doesnt leave a rice grain size of a tear behind it makes it a bad weld??? But yet BEFORE when i had the bad weld I was told it was bad because it didnt leave anything behind. WHICH its leaving stuff behind now and yet now its not enough again???

Who knew that building batteries was a skill developed over time :man_shrugging:

The long and the short of it is, you can do whatever you’re happy with.

But don’t get your knickers in a knot when you ask for opinions and don’t like them.

What im annoyed by is the fact that im told “check here” and when looking there i see others with the exact same welds as mine and told theyre fine. Its extremely confusing. I value yalls opinions greatly. That’s why i come here. But getting conflicting answers makes it difficult

Next up “battery builders club IS A SCAM”

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Because anyone is allowed to give battery advice. Not everyone should.