Solid spot welds on salvaged cells

loyd

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

Later floyd
 
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
 
loyd said:
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 :)
 
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
image_xarppj.jpg
 
loyd said:
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
image_xarppj.jpg
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
 
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
 
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.
 
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
 
Stop in Harbor Freight if you have one nearby. They have cheap knock off dremel type tools for about $10 that come with a handful of bits. They are nothing high powered or high quality but they should do a nice job on something that isnt too demanding of it. I have used it to successfully grind down some pocket clips and clean up salvaged cells in the past. It made easy quick work of it.
 
I have looked at all kinds of spot welders and finally decided on the KWeld.
I went with the recommended Turnigy Nano-Tech 5000mah 3S 65~130C Lipo Pack for the power supply and experimented.
For my system the E= 35.1 setting seemed to be a good setting. I finally got the courage to go to E=35.6 and the welds are perfect and consistent.
Negative side and positive side. I make a best effort to clean as much of the original spot weld leftovers off but have had no problems welding over them. Test tears have been very strong also no need to double pulse with the KWeld. I am very impressed with the unit.
I also purchased a Turnigy Graphene Panther 6000mAh 3S 75C Battery which gives me more run time.
Zoom in on the picture and you can see how consistent and good the welds are.


image_pfktfy.jpg


Wolf
 
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