kWeld - "Next level" DIY battery spot welder

Batteries, Chargers, and Battery Management Systems.
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garolittle   1 kW

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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 18 2018 2:45pm

I am assembling my new Kweld unit. The instructions are very easy to follow. Quick question. As you can see in the picture below, one of the bus bars is very close to the capacitor. The bus bar may actually be in contact with the capacitor. As you can see from the second picture, the bus bar is aligned properly with the holes. Is it ok for the bus bar to be this close to the capacitor? Thanks for making this product.
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Re: kWeld - "Next level" DIY battery spot welder

Post by spinningmagnets » Aug 18 2018 5:30pm

It "looks like" it will be fine, but...I'd take it off and hit the sharp edge next to the capacitor with a coarse file to create some airspace.

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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 18 2018 9:03pm

spinningmagnets wrote:
Aug 18 2018 5:30pm
It "looks like" it will be fine, but...I'd take it off and hit the sharp edge next to the capacitor with a coarse file to create some airspace.
Sounds easy enough. Thanks. :D I will give it a try in the morning.
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Aug 19 2018 4:51am

garolittle wrote:
Aug 18 2018 9:03pm
spinningmagnets wrote:
Aug 18 2018 5:30pm
It "looks like" it will be fine, but...I'd take it off and hit the sharp edge next to the capacitor with a coarse file to create some airspace.
Sounds easy enough. Thanks. :D I will give it a try in the morning.
I agree. But I am intersted to understand this from a quality viewpoint. In the design, both busbar and the leftmost MOSFET are flush. Is it possible that this bus bar is longer than it should be? This is how the dimensions should be like:
brass-busbar.png
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Re: kWeld - "Next level" DIY battery spot welder

Post by Trewella » Aug 19 2018 5:33am

I also just finished building my welder & noticed I had to push the bus bar to the left against the capacitor for the holes to align.

The legs of the capacitor were bent to the right, so I just eased the capacitor to the left, so the legs were straight up and down. This created a slight gap that I could see in the picture in the build instructions.

Frank has messaged me that there is no issue if the bus bar & the capacitor are in contact, as the bus bar does not heat up enough to cause an issue.

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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 19 2018 9:01am

I will double check but the bus bar appears to be exactly 75 mm in length. It looks like the capacitor may be “leaning right” but it is always possible that I accidentally bent it when installing the nuts and bolts onto the bus bar. See picture. It will all work out just fine. Thanks for being so responsive to your customers. Great work!
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 19 2018 9:38am

It worked. I very carefully and very gently pushed the capacitor so that the supports were straight up and down. You can now see a slight gap in between the capacitor and the bus bar. All is well. :)
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Re: kWeld - "Next level" DIY battery spot welder

Post by spinningmagnets » Aug 19 2018 9:53am

There is a pvc plastic heat shrink sleeve over most cylindrical capacitors. That is the easiest way to insulate and add the name/part-number.

Under that is a metal "shell" for physical protection. It can be steel, but is typically aluminum.

Under that is an insulator to protect the "roll" from touching the shell.

A capacitor is two electrostatic plates that are separated by a thin insulator (*dielectric). They can be produced in many shapes. The type of dielectric material and the precise thickness determines how much "static" charge is held onto the two plates by electro-magnetism.

In order to create a lot of plate surface area, the common cylindrical capacitors have two very long ribbons that are laid against each other with the dielectric between them. Another insulator is laid on top, and the long ribbon assembly is rolled up into a cylindrical shape.

The bus bar should not be touching the cap, but as long as there is no shock or vibration, the plastic wrap will not be cut. If the plastic wrap is cut by a conductive bus, the underlying metal shell of the cap is still insulated inside, however, that should not be allowed to happen.

The kWeld is not designed to be dropped from a table-top to the floor, but such an event can happen in real life, and a few minor precautions taken during the assembly can save you time, trouble, and money to reduce the chance that a minor repair would ever be required.

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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 19 2018 2:03pm

Done! Just waiting on the power source from Hobbyking so hopefully I can run some experiments by next Friday. Thanks to everyone for the tips and suggestions.
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Re: kWeld - "Next level" DIY battery spot welder

Post by fjaromczyk » Aug 23 2018 8:20am

Hi there,
I bought the kWeld with the ultracapacitor pack and it works great!
I have a question about the material of the electrodes - you specify it is telurium copper.
Why such a choice - was it due to availabity/price ratio or was there some other reason?

I am asking because Sunstone Welders has a electrode selection guide and for instance for nickel, they recomend GLIDCOP (copper with aluminium oxide particles) or RWMA 2 (copper zirconium).

Many thanks,

Filip

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Re: kWeld - "Next level" DIY battery spot welder

Post by spinningmagnets » Aug 23 2018 12:34pm

The kWeld is designed to deliver a welding pulse that is extremely short, measured in milliseconds. It is very helpful to have electrodes that have a very low electrical resistance.

If the cables were clamped to the outside of the electrode, and the tip did not need to be easily and cheaply replaceable, pure copper would be a good choice. Customers have preferred having a replaceable tip, and the best design so far uses pure copper rods as the replaceable tip, but doing so requires drilling a socket into the conductive holder.

If the socket was shallow, there would not be enough physical contact between the pure copper tip and the conductive electrode holder. Machining a deep hole in pure copper is difficult, due to how soft the metal is. Tellurium C14500 Is reasonably machinable, but still has a conductivity of IACS 93/100 of pure copper.

The brass electrode holders on the popular Sunkko spot-welder are very easy to machine (cut and drill), but the conductivity of brass is roughly 28/100 IACS. I will certainly look into the two types you listed to see if they might provide some benefit over C14500

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Thanks for posting those options. The RWMA-2 option has a slightly lower conductivity of 85/100, so there is no benefit to using them in this application, however...

The GLIDCOP material is actually a useful option for high-energy welds. If the pure copper tips get so hot and soft that they begin sticking to the material, the "go to" electrode is Tungsten. Although Tungsten has a very high melting temperature, they also have a low conductivity rating of IACS 32/100. This means tungsten electrodes will get VERY hot.

The GLIDCOP material has a conductivity of 92/100, which is very good. For our purposes (spot-welding nickel buses onto 18650 cells) the pure copper tips are working well, but...should you begin using the kWeld for high-energy welds that soften the tips so much that they begin sticking to the material, GLIDCOP is a MUCH better material than pure tungsten. (WCu/ Tungsten-Copper RWMA-11 was my previous better option for high energy).

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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 23 2018 7:00pm

spinningmagnets wrote:
Aug 23 2018 12:34pm
.....should you begin using the kWeld for high-energy welds that soften the tips so much that they begin sticking to the material, GLIDCOP is a MUCH better material .....
Would it work better for those attempting to spot wel .10 mm copper strips? Just curious.
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Aug 24 2018 6:38am

garolittle wrote:
Aug 23 2018 7:00pm
spinningmagnets wrote:
Aug 23 2018 12:34pm
.....should you begin using the kWeld for high-energy welds that soften the tips so much that they begin sticking to the material, GLIDCOP is a MUCH better material .....
Would it work better for those attempting to spot wel .10 mm copper strips? Just curious.
Our main reasons were as much electrical conductivity, and better machineability. Browsing C18150 gets me "The addition of Zirconium to chromium copper improves creep resistance at high operating temperatures and reduces sticking of electrodes to the work during spot welding of galvanized/coated materials." (http://www.cadicompany.com/products-C18 ... conium.php) which sounds very interesting. This is also supposed to have better machineability, and it good be a good future option. But I wouldn't expect to be able to get rid of electrode wear and sticking of any type of copper. They will always be consumables, and require cleaning and reforming during use.
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Re: kWeld - "Next level" DIY battery spot welder

Post by bernieke » Aug 24 2018 7:13am

I was just about to start assembling my kWeld and kCap, and wanted to cut the housings first.

But I see the latest versions all use the face entity types, which my lasercutter software doesn't recognize. I don't see a way to change this to (poly)lines in qcad either.

I've found a 2d version of the latest kWeld housing (with holes instead of the long lines for ventilation), but I only find one version of the kCap housing.

Before I start redrawing the kCap file using polylines, would anyone perhaps already have a 2d version?

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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Aug 24 2018 10:12am

bernieke wrote:
Aug 24 2018 7:13am
I was just about to start assembling my kWeld and kCap, and wanted to cut the housings first.

But I see the latest versions all use the face entity types, which my lasercutter software doesn't recognize. I don't see a way to change this to (poly)lines in qcad either.

I've found a 2d version of the latest kWeld housing (with holes instead of the long lines for ventilation), but I only find one version of the kCap housing.

Before I start redrawing the kCap file using polylines, would anyone perhaps already have a 2d version?
Just let me know which format you prefer and I'll make you an export.
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Re: kWeld - "Next level" DIY battery spot welder

Post by bernieke » Aug 24 2018 10:16am

Just a regular 2D dxf like the first version of the kWeld enclosure would be perfect!

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Re: kWeld - "Next level" DIY battery spot welder

Post by bernieke » Aug 25 2018 2:09am

It wasn't so much work to redraw it with polylines after all, luckily all radii were nice round numbers :)

I've attached the resulting dxf (I had to zip it as the forum software didn't allow me to attach the plain dxf.)

You can use it however you see fit.

Thanks for all the good work with kWeld/kCap!
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 26 2018 10:54pm

So I recently received my Kweld unit and lipo battery. It was easy to assemble and I ran a few experiments this weekend. Although I am more interested in using individual cell fuses, I wanted to try out the Kweld spot welder on nickel plated .15 MM copper strips. The welds below were achieved using between 60-80 joules and the results were good. As you can see from the video clip, the weld strength would need to increase for a go kart application but I was intentionally running it with fewer joules to see what would happen. Keep in mind that these are the .15 mm copper strips that I recently “nickel plated” using an electroplating technique. Spot welding .15 mm and .20 mm pure nickel strips was extremely easy. I wanted a real challenge so I immediately transitioned to the nickel plated .15 mm copper stripes.

https://youtu.be/EdBI4S8Ug3E

The Cell-Level fusing with 24 AWG tinned copper wire was even easier. I achieved the results below using 25-30 joules. I will try higher joules in the coming days to improve the weld strength but I am very pleased with the Kweld unit so far.
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I highly recommend the Kweld unit. Excellent product and a good price.
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 26 2018 11:14pm

By the way, special thanks to Frank for answering my questions regarding the Kweld unit. I do not know how you keep up with all these emails. :lol:
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Aug 26 2018 11:46pm

garolittle wrote:
Aug 26 2018 11:14pm
By the way, special thanks to Frank for answering my questions regarding the Kweld unit. I do not know how you keep up with all these emails. :lol:
me neither sometimes ;-)

Your needed energy levels appear too high for me, can you please check and repeat calibration a few times, pressing the tips hard together, and see if you get repeatable results (keep the foot pedal down after "short")?

Cheers
Frank
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 27 2018 6:12am

Will do and thanks. I noticed that the amps stayed near 1,000 most of the time. Is that normal?
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 27 2018 6:17am

I also had 2.77 milliohms of resistance at calibration which seemed within the normal range. Awesome product.
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Re: kWeld - "Next level" DIY battery spot welder

Post by BVH » Aug 27 2018 4:17pm

Placed a pre-order. Excited about receiving it.

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Re: kWeld - "Next level" DIY battery spot welder

Post by PaulD » Aug 27 2018 4:45pm

Got mine hooked up, and it's producing good welds. It's replacing an arduino timed DIY welder. Only using 30J for 0.2mm nickel. I'll be experimenting with higher energies soon. I just need an on/off switch since the battery terminals are bolt-on. I'll try a big high current boat switch and see if that holds up and doesn't add too much resistance.
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Re: kWeld - "Next level" DIY battery spot welder

Post by garolittle » Aug 27 2018 4:48pm

:shock: Now that’s what I call an incredibly good set up!
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