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kWeld - "Next level" DIY battery spot welder
#1
It originally started as a one-off, but through continuous support from

https://endless-sphere.com/forums/viewto...14&t=89039 and http://www.eevblog.com/forum/projects/gu...ting-here/ , I am now able to offer my solution as a kit for purchase.

https://www.kicksurfer.de/index.php/prod...elder-kit/

[Image: ?action=dlattach;attach=329176]

[Image: ?action=dlattach;attach=332388]

Here are some key specs of my system:

Hardware:
  • Input voltage for welding: 12V – 30V
  • Extremely rugged MOSFET-based power switch and mechanical current bus design
  • Maximum switch current: 2000A
  • Power switch internal resistance: 120µOhm
  • Logic supplied directly from battery – no need for a separate auxiliary power supply
Software:
  • Central weld control algorithm uses a Joule metering approach instead of a simple timer, eliminating the need for two-pulse firing and providing more consistent welds – the amount of energy that is deposited into the weld spot is always kept constant
  • Ability to detect a failed weld, and acoustic feedback to the user
  • Manual mode, triggered from external switch
  • Automatic mode, accompanied with a warning sound and triggered with a 0.5sec delay, once the system detects that both electrodes are in steady contact with the weld material
  • Audible feedback of weld process completion
  • Numeric feedback from an executed weld, assisting the user to achieve best results: deposited energy amount, required pulse time for this energy, measured current flow, measured ohmic resistance of weld spot

It is not the cheapest solution on the market, but it has shown bullet proof stability. It is more than capable of welding 0.3mm nickel strips.

These videos show the system in action:
https://youtu.be/Ceos88VO6p4
https://youtu.be/fWXphoDE_H8
https://youtu.be/JR3GJYScquc
https://youtu.be/9-CQd02EDIs

Cheers
Frank
BlueSwordM likes this post
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#2
Nice design. Impressive. Especially the sparky parts Tongue

Couldn't you make a holder that holds both electrodes? That would minimize electrode contact. The holder could be adjustable in width the electrodes are positioned.

Nice work, though. A lot better than what I could of come up with Wink
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#3
My experience with soldering is dirty and error prone and not good for my iron lung so I may be looking for something. 


Other than wanting to try one, I don't know anything about them. If you send one to me I'll give it an honest review, leveraging my extensive experience picking peaches. Tongue

It is neat that it runs from a battery though I think I'd want to run it from mains.

 

Your ring looks like it was zapped with 2000A but I don't judge. 

https://www.youtube.com/watch?v=JR3GJYScquc

Oh yea, we would get along just fine... safety f... whatever! Stuff happens.

Seems simple. I like it.  Best of luck!
chamiscastillo likes this post
Runs with low voltage
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#4
A battery spot welder this well engineered... This could probably sell for 500$, easily more.
The power of lithium ion is in our hands!
We'll show them what we're made of!
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#5
I like it alot. very nice. I also recomend a holder for the electrodes like the commercial versions have. Could be 3d printed and then spring tensioned so you get even pressure.
Korishan and BlueSwordM like this post
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#6
hmmm, the quoting button doesn't seem to work on my mobile, so I'll respond this way.

At first hanks for your best wishes all!

@Korishan: if this business grows far enough then I plan to resell one of the professional probes. But there is also a drawback to fixed probes: the autimatic mode that my systrm has triggers on probe contact. it is easy to push down one probe, keeping the nickel strip in place, and then push down the other one. This way welding is very fast with my solution. Maybe 1.5secs per weld. I don't know how well the handling can be with a fixed probe armature.

@kazbach: please feel free to order one, I will give a discount to everyone making a review: 50% off the labor cost.

You can run my system from a Lipo (they don't like this treatment and lifetime will probably be short), a lead acid battery (car batteries do the job), or from AC. This requires a large capacitor though (several F, with very low ESR), which is quite costly - hard to get below 100€ only for that. This will be one of ny next projects.

The ring was like that, it's not an accident :-)

@daromer: I thought of that, but 3d printed parts typically have low heat resistance and will probably melt when this is used on high duty.
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#7
Maybe you could do a combination of manual and automatic mode. In the sense that you could have a holder for the two electrodes with a small button on it. When the button is pressed, that's when sensing goes through the contacts and the auto-mode kicks in.

I was thinking about keeping the welds evenly spaced and minimizing 'ol sparky. Smile

I find it interesting that you can hold onto the electrodes bare handedly and not get shocked when the thing fires off. That just baffles me. I know it's voltage, but still. It can still hurt if it goes the wrong way.
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#8
(07-17-2017, 12:04 PM)Korishan Wrote: Maybe you could do a combination of manual and automatic mode. In the sense that you could have a holder for the two electrodes with a small button on it. When the button is pressed, that's when sensing goes through the contacts and the auto-mode kicks in.
I've also seen this on other spot welding probes, that would definitely make a 3D printed part interesting. I have put making this task to the others, including making a electronics housing design. Using the system without protection would be very dangerous.

I plan to make another video, just letting the camera film while me making a complete battery pack. I am sure that the automatic mode can be used reliably as it is now, I think the audible "contact! contact!" feedback will help a lot, and an additional switch will not be necessary. I'm curious how this will work out.

Maybe also worth to mention: there are generally no sparks when the contact to the nickel strip is good, and when it is kept steadily. Whenever you see a spark in my video, I made something wrong. For example, hesitating right in the moment of auto-firing. Or welding through the battery, damaging it. Or destroying cookie cans. (Although that was fun, not wrong Cool )

(07-17-2017, 12:04 PM)Korishan Wrote: I find it interesting that you can hold onto the electrodes bare handedly and not get shocked when the thing fires off. That just baffles me. I know it's voltage, but still. It can still hurt if it goes the wrong way.
Why should you get shocked by any system that works with 12V? Current is impressive, but it is only harmful when directed through your body. In this case, it is 1000A through the weld spot, and a few hundred microamps through my hands.

The highest voltage is developed during the turn off transition at the end of the pulse. That is in the range of 50V, but only for a few microseconds.

The SELV law limit (safety extra low voltage) her in Europe is 60V DC, and that was chosen because this the maximum voltage that you don't feel yet when touching it directly with whatever part of your body. (Except your tongue)

(07-17-2017, 12:04 PM)Korishan Wrote: I was thinking about keeping the welds evenly spaced and minimizing 'ol sparky. Smile
I have no experience with monolithic probe holders, but that is exactly what my biggest concern is with them: that you do not recognize it when you don't distribute the pressure on the electrodes evenly - that's when you get sparks. That is probably much simpler when having one of them in each hand. And I had a simple idea regarding how to get even spacing, it will also be in the video.
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#9
On the hand held probe i got there is springs on both probes. so you press the tool down and then press the foot pedal.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#10
(07-17-2017, 03:49 PM)daromer Wrote: On the hand held probe i got there is springs on both probes. so you press the tool down and then press the foot pedal.

Can you show me a picture please? Is that one available somewhere as a replacement part?
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