JP spot welder

Can you give a little more detail on the electrodes? This seems to be a trouble spot for many of the DIY welders. The Sunstone units have special electrodes and I suppose one could just buy those, but it seems yours work just fine. Just hard copper?
 
Sunstone has some great electrodes, I'm planning on buying a few and testing. They also have few materials to chose from, copper, tungsten, tungsten-copper, and molybdenum.
I use pure copper 10mm2 solid wire, with tips machined to have a smooth cone like shape with half-globe like ending. I'm thinking on getting a custom tool done which would make it easier and faster to get such shape and also improve consistency, because this material works well and sunstone tips would bring up the cost, and I'm not sure if it's necessary.
Also my attachment system allows attaching tips to wire without soldering, so I can use any material if I wanted to, not just pure copper.
 
Well that's pretty fast! Fastest I've seen :)


No luck with 0.1 aluminum. It's really easy to weld, even with one battery and short pulse time, but once it welds, it gets really weak, and easily pops of. It leaves holes in aluminum, but almost no material on cell itself. Maybe I should try with 0.2 or 0.3 mm? It's pretty cheap, this would be most economic way to weld cell.
 
riba2233 said:
Well that's pretty fast! Fastest I've seen :)


No luck with 0.1 aluminum. It's really easy to weld, even with one battery and short pulse time, but once it welds, it gets really weak, and easily pops of. It leaves holes in aluminum, but almost no material on cell itself. Maybe I should try with 0.2 or 0.3 mm? It's pretty cheap, this would be most economic way to weld cell.
Click to expand...
I looked into it and Aluminum just won't be a good idea. It's far too soft once welded. and you need a very specific grade, hard to find in sheets, for both weld-ability and good electrical conductivity.
 
riba2233 said:
Sunstone has some great electrodes, I'm planning on buying a few and testing. They also have few materials to chose from, copper, tungsten, tungsten-copper, and molybdenum.
I use pure copper 10mm2 solid wire, with tips machined to have a smooth cone like shape with half-globe like ending. I'm thinking on getting a custom tool done which would make it easier and faster to get such shape and also improve consistency, because this material works well and sunstone tips would bring up the cost, and I'm not sure if it's necessary.
Also my attachment system allows attaching tips to wire without soldering, so I can use any material if I wanted to, not just pure copper.
Click to expand...

I have their tungsten copper, RWMA II and RWMA III electrodes.
I still use pure copper for nickel and copper, but once these wear down a bit more, I'll try the RWMA II electrodes.
 
Yeah, that would be deadly :) 12 V nominal is absolute max. Mosfets loose their ability to withstand surges exponentially with higher voltage. I don't know if you've seen technical topic, and I think you did because you've answered, but one guy had great results with 3s2p a123 20 ah cells. So, 40 Ah and 9 V is more than enough, you don't even need 80 Ah.

\/ampa said:
Hello all,


I have lurked since some time and have build this Spot Welding machine but have used 2x3s 20Ah A123 cells and 8x MOSFETs. I welded several hundred cells already and the MOSFETs highest temperature was little over 40°C. The cables are 25mm² OFC copper and about 60cm long. The electrodes are made of 5mm hard copper and even this short they get very hot after 50 fast weld´s.
The welds in the last picture are made with 0.3mm nickel strip. Its super strong. The sparks fly upwards. While welding i have to wear protective glasses.
Click to expand...
 
Hello JP I'd like to weld together some 18650 packs - your solution seems to me to be both brilliant and elegant. I'd like you to send me one but am clueless as to how to work the transaction - would you please explain to me the ins and outs of placing an order? Thanks so much, michael
 
Vgs is gate voltage, that doesn't matter. You should look at Vds, which is drain voltage. But that datum doesn't tell much, we should look at one graph, called maximum safe operating area. On that graph you can see that current on 9V and 10ms pulse is two times higher than on 12V, and 14 times higher than on 20V.
 
Can we talk materials a bit? I don't get why nickel might be preferable to copper, but obviously there are good reasons since it's used extensively not just by ES builders but by a wide range of commercial manufacturers.

Copper is the clear winner in terms of conductivity and price, and weldability seems to be comparable, judging by riba's and okashira's experience.

I suppose nickel's advantages would be corrosion resistance and structural strength. As long as oxide removal is properly done (sanding, solder flux) prior to welding, corrosion doesn't really matter once the pack is built, right?

What else haven't I thought of? No experience in this area so I'd like to get a better sense of things from those who have been around this particular block.
 
Well, I think that you've given yourself the answer :) Nickel is reliable and tried out, you don't have to be so careful while welding not to brake it etc. Also many Chinese packs are made using those weak welders that can barely weld 0.15 mm nickel, so they could only use 0.05 copper which is pretty weak and you have to know what you are doing while using it.
 
I've decided to stop welding copper for now. It's too unreliable. Id say 80% of the welds are good, but there are too many other issues with it as well.
Nickel welds on the other hand are good 99% of the time.

I ordered some 0.15mm copper to try though. Maybe it will be better. Might need to go up in voltage. :)
 
The Mighty Volt said:
Oh dear. My whole point of buying this was because it worked on copper. My existing welder already does nickel very well.
Click to expand...

Tungsten or Molybdenum electrodes may help. I was using copper.

Copper is too thin ... .15 may work. But now I gotta build a whole new board.

I still do use it, but only for re-enforcing a bus bar on the + or - of the pack. I'll only stack it on nickel, then place another layer of nickel on top (and ensure the nickel overlaps the copper so i'm welding nickel to nickel on both sides of the copper.)
 
TBH, okashira uses old version of code, so he doesn't have optimal pulse times. He will get new version. I'm getting great results so far. But copper definitely isn't foolproof like nickel, you need to be concentrated ans use proper technique. That can be a problem with hand held electrodes.
 
riba2233 said:
TBH, okashira uses old version of code, so he doesn't have optimal pulse times. He will get new version. I'm getting great results so far. But copper definitely isn't foolproof like nickel, you need to be concentrated ans use proper technique. That can be a problem with hand held electrodes.
Click to expand...

Yes, I hope the new 1st pulse time will help. I also orderred .15 copper and now I will use the irf1324 mosfets which I think will be better at long pulse time then the 3805 I was using.

Another thing, only pure tungsten or moly electrodes are recommended for copper, that would probably help too.
To avoid sticking with copper, i developed the technique to very slowly roll the electrode off the weld during the pulse and after the pulse. this keeps the copper from fusing to the electrode. And you want to roll the electrode and keep pushing down so you don't pull on the weld you care about (copper to nickel).

You probably already do this subconsciously. I figured it out after I was teaching my buddy to weld. He kept getting sticking at the exact same settings I was using... it was really baffling. I would sit down and do the same weld with same pressure and get no sticking.
I finally realized it's how you manipulate the electrodes in the split second after the weld that really determines if you don't get sticking.

I think rmwa II or III electrodes will fix all that, but it's nice to use solid copper which costs $0.05 per electrode. :-D
 
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