kWeld - "Next level" DIY battery spot welder

[eee291]

I have plenty of tungsten electrodes around the shop.

But that's not what I was asking, I was wondering if one electrode being consumed faster than the other one was normal or not.

 

[spinningmagnets]

Some of the energy is being dissipated as heat, and we need that heat to melt the nickel in two tiny spots. However, since some of the energy dissipated at the mid point of the circuit, there is less energy in the last half of the circuit. So the difference in tip wear is normal.

You could swap the two electrodes in each holder every few hundred welds (from one holder to the other) to keep the wear even, as an option...

 

[999zip999]

Tip shape and finishing means a lot whether it's a point or a tip that looks like a snow cone. Yes got to keep working at it and see what works best. But you can't leave it as a point. My old neighbor had a TIG welder and a $600 Swiss electoral conditioner. It would cut cone the tip rotate the tip to a precise point that somehow he figured out the radius and condition but it was quite adjustable. So with so many variables as tip pressure and everything else the tip can be shaped and many different styles.
Have you tried the tungsten for tips ?

 

[eee291]

I haven't tried the tips on this welder yet.
I still need to modify the welding Pen a bit and add some ring terminals to it.

I bought some 2.4mm WC20 and WL20 tungsten electrodes.

 

[999zip999]

H.F has those small diamond disc put in a drill pointing up or flat. Just find a way to brace your hand in your hand. And spin. Tungsten 1 hard weird metal.

 

[eee291]

I have plenty of ways to sharpen the tip that's not the issue really.

I just wanted to know if everyone was experiencing the same thing as me.

 

[ichiban]

tatus,

Please find a way to extend the length of the welding electrode cables since it is hard to weld with stock short cables even with 14S5P I just did.

Just like they did in this thread JP spot welder :

https://endless-sphere.com/forums/viewtopic.php?p=1434926#p1434684

It will be awesome whenever we need to weld larger packs.

thank you

 

[eee291]

I welded a 300 Cell Pack with the stock cables just fine.
You need to have the Welder above the Cells, similar to this:

 

[spinningmagnets]

I haven't built this yet, so I'm a little embarrassed to suggest anything, but...Here is my plan for a welder stand. The two arms swing back to store alongside the center platform, so it is easier to store when I'm not using it.

My goals were several. One of them is to make the electrode cables as short as possible, since I want to explore the higher energy levels on the kWeld. Long cables seem to sometimes have an issue with inductance, which I don't really understand.

 

[tatus1969]

I have made about 3000 welds with this thing and am experiencing some accelerated tip wear when comparing it to the other one.
The electrode connected to the B+ fuse has been reshaped twice while the one connected to the MOSFETs looks almost like new in comparison.

That suggests that you have a fair bit of arcing. The accelerated electrons in the ionized gas hit the copper tip and cause damage, in addition to the created heat. That's why it is always the positive electrode that wears out. There's not much that can be done against this. Reducing the voltage and current should help a bit, and using clean tips and enough force to avoid arcing. My personal setup (3S, 1400A) doesn't arc most of the times, except that I see some sparks emitting from time to time.

 

[tatus1969]

tatus,

Please find a way to extend the length of the welding electrode cables since it is hard to weld with stock short cables even with 14S5P I just did.

Just like they did in this thread JP spot welder :

https://endless-sphere.com/forums/viewtopic.php?p=1434926#p1434684

It will be awesome whenever we need to weld larger packs.

thank you

I'm afraid but that cannot be done easily. The reason to have short cables isn't only to keep resistance low (we could use 6AWG to compensate this). It is because loop inductance plays a huge role when interrupting the current at end of pulse. Current through an inductor is stored energy, just like voltage across a capacitor. This energy has to go somewhere when interrupting the current, and that's why kWeld has so many transient voltage suppressor (TVS) diodes. To make things worse, doubling the current quadruples the stored energy because it is a quadratic equation.

It is possible to use kWeld with longer cables, but the current limit has to be lowered in such a case. You do this by dialing in the actual length through the configuration menu. Not doing this puts the power switch in danger, and seeing the JP welder in those pictures I won't give it a long lifetime (unless the current is only moderate, maybe below 1000A).

 

[ichiban]

I welded a 300 Cell Pack with the stock cables just fine.
You need to have the Welder above the Cells, similar to this:

Thanks for sharing, eee291.

Your set-up is a perfect welding station ! Add a pneumatic plunger, it will become a industrial welder.

+ Did you also mod the welding electrodes ? They look thinner. How do they weld ?
+ How thick nickel/copper can you weld with these new set-up of yours ?
+ How many Ah is your lead-acid batt ? How many welds does your battery last ?


Mine is a stationary unit with 6 ultra-caps with PSUs and plugging into wall-outlet. My intention is just a DIY home-use unit. I just don't have time/resource to do a top-notch unit like yours. That's why I ask whether tatus can extend the welding cables. I aware that longer cables might affect higher R & L but tatus should be the one who knows the best about his machine. I just request as a user.

But if needs arise, may be I might follow your footsteps !

I haven't built this yet, so I'm a little embarrassed to suggest anything, but...Here is my plan for a welder stand. The two arms swing back to store alongside the center platform, so it is easier to store when I'm not using it.

My goals were several. One of them is to make the electrode cables as short as possible, since I want to explore the higher energy levels on the kWeld. Long cables seem to sometimes have an issue with inductance, which I don't really understand.

View attachment 2

spinningmagnets, your design sure looks interesting. Do you have to use 2 hands to push down the 2 welding arms together ? Then when you let go, both arms will swing back up ?


Anyway, I still like the idea of longer welding cable. Another 50-cm longer on each will make a lot of differences to me. I just don't like the welding unit to move since mine is quite bulky with the welder unit, caps bank, 2 PSUs, 2 regulators, heatsink and etc. The existing unit give me a little inconveniences after welding already. You know what I mean...








View attachment 1

 

[ichiban]

May be it is also like tatus said, the longer the welding cable the higher energy stored in the inductance L and thus it will find a way to keep that current to flow. Resulting in fire back to the mosfets in the circuit for every shot of welding. Premature life of mosfets can be expected.

 

[eee291]

It is not my design, you can read about it here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=89039&start=400#p1406999

 

[spinningmagnets]

spinningmagnets, your design sure looks interesting. Do you have to use 2 hands to push down the 2 welding arms together? Then when you let go, both arms will swing back up?

Yes, I only drew the coil return spring on the left arm, but they both will have them. If someone wants an elevated stand (where the battery pack can be moved around under the welder), the arms don't need to fold back (for storage). I just thought that since it was easy to do that, why not? Using three posts instead of four means it won't wobble.

Shannon Williams on facebook is getting very good results with 4S Headway LiFePO4 (12V) feeding a set of kCap units. The Headways are kept topped off by a common 12V car charger. I mention him because he is a heavy duty user, and he has found that by experimenting with the pressure you apply with the tips, it can have an effect on the quality of the welds.

I'm working on designing an easy way to have a single pull-down arm to actuate the two probe-tip arms. They will incorporate coil springs to apply compression, but will also have bolts to adjust the pre-load on the springs, so the pressure on the tips is consistently the same load on every weld. I'm not saying this is the best idea for me, or even a good idea for anyone. I just wanted to share some ideas...

 

[tomjasz]

.

+ Did you also mod the welding electrodes ? They look thinner. How do they weld ?

Those are the electrodes sold with the Sunnko China junk.

 

[tatus1969]

Mine is a stationary unit with 6 ultra-caps with PSUs and plugging into wall-outlet.

Awesome build!

That's why I ask whether tatus can extend the welding cables. I aware that longer cables might affect higher R & L but tatus should be the one who knows the best about his machine. I just request as a user.

I wouldn't want to modify the standard product as I have a larger cable assembly order running already, but I also sell them as loose parts (https://www.keenlab.de/index.php/product/kweld-cable-electrode-holders/). You could use this set as the basis for a custom cable assembly with longer and thicker wires like 6AWG. Just make sure to tell the welder the actual cable length so that it can adjust its overcurrent threshold. As you are using kCap which delivers "only" 1100 .. 1200A, you shouldn't run into trouble anyway.

 

[garolittle]

I welded a 300 Cell Pack with the stock cables just fine.
You need to have the Welder above the Cells, similar to this:

Really nice set up.

 

[PKGB]

What an amazing thread! Fantastic stuff! I've never wanted to start building or repairing batteries, mainly because of the available spot welders being unreliable. This unit will be a real game changer, making battery work much safer. The question is, when will I be able to get a kWeld all the way down here in New Zealand?

 

[ossivirt]

What an amazing thread! Fantastic stuff! I've never wanted to start building or repairing batteries, mainly because of the available spot welders being unreliable. This unit will be a real game changer, making battery work much safer. The question is, when will I be able to get a kWeld all the way down here in New Zealand?

In first post there is link where to buy. I assume he ships to New Zealand also since it's part of this planet

 

[PKGB]

What an amazing thread! Fantastic stuff! I've never wanted to start building or repairing batteries, mainly because of the available spot welders being unreliable. This unit will be a real game changer, making battery work much safer. The question is, when will I be able to get a kWeld all the way down here in New Zealand?

In first post there is link where to buy. I assume he ships to New Zealand also since it's part of this planet

"SOLD OUT"

 

[999zip999]

What small planet Big world. They will be in stock again as I think this is the best battery do it yourself welder on the planet at the moment. At a diy price . Read up. Lots of info about good results.

 

[tatus1969]

New stuff is in production, I expect to receive that within one or two weeks from now! 8)
NZ is possibly, but you'd need to calculate ~40€ for shipping.

 

[tomjasz]

An electronic dunce here. That said I've been looking at the China made kits. Not to buy but I'm curious how they use a microwave transformer(?) rather than batteries?

 

[spinningmagnets]

Microwave Oven Transformer / MOT

https://endless-sphere.com/forums/viewtopic.php?t=85023

Resistance Soldering Unit / RSU from a MOT

https://endless-sphere.com/forums/viewtopic.php?t=89289