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Solid spot welds on salvaged cells
#1
Sorry. Can not post into a thread older then 3 months.

I have difficulties to spotweld onto salvaged cells.
On new cells I get a solid connection. On the used ones one out of 10 is solid.
Is there a trick I'm missing? Am I not pressing hard enough or are the bumps on the cells standing out to high?

Andy
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#2
Do you have flush cut pliers if not you can clip off most of the old welds with one.

Later floyd
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#3
I ordered one last night.
What settings do you use on the spotwelder?
I burned one open today. But with lower amp it does not work to good. Maybe it is also due to cheap china nickel strips.

Andy
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#4
(03-14-2020, 10:55 PM)loyd Wrote: Sorry. Can not post into a thread older then 3 months.

I have difficulties to spotweld onto salvaged cells.
On new cells I get a solid connection. On the used ones one out of 10 is solid.
Is there a trick I'm missing? Am I not pressing hard enough or are the bumps on the cells standing out to high?

Andy
hi  loyd
i faced similar problem
i used a small size hand sanding machine to remove the small portion of spotwelds left on the cell
you may try the same  Smile
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#5
Well, I tested with nickel from a battery pack. Its the same. So it should not be low quality nickel.
I think I dont get the settings right. One weld is good, the next one is bad.
And there are no sparks. It is more a glowing.
When you tear of the nickel, the welding spots are no spots. They are more like needle heads or bigger.

Andy
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#6
(03-15-2020, 11:59 AM)loyd Wrote: Well, I tested with nickel from a battery pack. Its the same. So it should not be low quality nickel.
I think I dont get the settings right. One weld is good, the next one is bad.
And there are no sparks. It is more a glowing.
When you tear of the nickel, the welding spots are no spots. They are more like needle heads or bigger.

Andy
which welding machine are you using the current doesnt seem enough thats why you dont get the spark
you need to increase the current and check
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#7
Im using a DIY MOT Spot welder with a chinese board ( NY-004).
The Amps are at maximum setting. Theoretically it should output around 800 Amps.
475 windings primary and 3 windings secondary

Andy
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#8
Sparks are caused primarily from a bad connection between the probe and metal. The spark is caused by the current jumping through air. Glowing is fine. Perhaps the duration of the glow isn't enough to finally fuse the two pieces of metal.
If the metal has too much oxidation on it, it will be very hard for them to fuse. It's just like soldering without flux.

Welding can be tricky between different brands of cells because the casing can be different thicknesses. If you blow holes in some cells from the amps too high, go lower on the amps and make the pulses longer.

On your MOT Welder, is it a single pulse, or multiple pulses? It's possible you may need to add in multiple pulses if only using singles. This can either be done with hitting the button in the same spot, or adding more circuitry to do the double/triple pulse.
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#9
My MOT welder is a single pulse.
I tried with multiple pulse hitting the button more often.
My best result was with maximum Amp and 200 ms on the Pos+ end. Same setting on the Neg- end is the picture above.
Longer than 200 ms it starts to burn or damage the cell. The same happens when I pulse it in total time 300 ms.
Lower Amp and longer pulse time does weld to weak.
I find it almost impossible to weld to the Neg end of a used cell or a cell with a previous welding attempt.

edit: just recalculated the transformer. Max output is 690 amp

Andy
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