kWeld - "Next level" DIY battery spot welder

[tatus1969]

I read all 30 pages of the forum with great interest. I am very sorry that I have already spent money on Chinese spot welding. It would be better to buy from you. My welding does not contain any protection. I don't want to change transistors often. Suppressors and diodes I will put in addition. But this is not enough. I want to make a small board based on comparators to track currents below 600A and above 1200A. So that she just turns off the driver. I have a few questions.
1. Does the IR44252 work well enough. He has a current of 0.3A.
 2. What pause is needed before starting to measure the voltage across the transistors. The tension does not rise instantly.
3. What are the voltage levels at a current of 1200A on transistors? Tee counted the voltage according to Ohm's formula or real measurements.
I have seen only one oscillogram of voltage measurement across transistors. And I didn't understand everything. If this is not a commercial secret, please answer my questions.

Not sure what your plan is. Do you want to extend your Chinese spot welder? This is probably a transformer based AC current system, where switching is done by SCRs and not MOSFETs.

[Uho]

I have 3000F capacitor spot welding. I bought capacitors separately. I can use either two or four capacitors in series. I bought a separate control board and DC-DC 20A. Order is still in transit. I am planning to charge capacitors current  up to 10A. I have not yet decided whether it is necessary to disconnect the charge of the capacitors during welding. If two capacitors are enough, then I plan to use such a balancer circuit. Attached the diagram. The Chinese do not put up any protection. There are many reviews about the combustion of transistors. Therefore, I want to make a current limitation 1200A.

[tatus1969]

Attached the diagram.

Your circuit should have a resistor between opamp output and transistor bases to limit their current in case of strong capacitor imbalance. Not having that means that base current is only limited by the opamp's drive capability. And is it your intention that the transistors dissipate all the excessive energy? Make sure they are big enough then and have good cooling. Also, have you considered the stability aspect of your circuit? I'd add provision of bandwith and gain limiting components of the opamp when making the design so that you can play with that. Or make a simulation with all parasitics as well as the actual chosen components to check the dynamic stability.

There are many reviews about the combustion of transistors. Therefore, I want to make a current limitation 1200A.

I see. You want to interrupt current as soon as it hits the limit, right? IR44252 should be good enough, but make your calculation of the injected power into the MOSFET die based on flowing current (=1200A) and turn-off slope (better do actual measurement with a scope). The resulting energy should not exceed the maximum avalanche energy of your chosen MOSFET. Do *not* multiply by the number of MOSFETs, because the turn-off energy may be dissipated by just one of them when they switch differently.

[Jiri_L]

Hello All,
I have no time to build up my own blocks, I have two unopened boxes of 18650 Li-ion from LG Chem.
Samller box 100 pcs of INR18650MG1, capacity 2900 mAh
Bigger box 200 pcs of INR18650F1L capacity 3350 mAh

Please offer the price, I want to sell it as a box not per cell, payment via PayPal or bank transfer, I can manage delivery with EU via DPD Carrier.

Thank you very much.

Greetings,
Jiri

[nexus]

Hi there,

I am planning to purchase kWeld, kCap, and kSupply together. Are 3D models available for these boards so I can design an enclosure for these components?
Also, has anyone found or used CAD models for the recommended HSTNS-PR0 server psu? Just wondering if there is something out there before I go crazy with modeling as usual 

Cheers

[syau]

I have 3000F capacitor spot welding. I bought capacitors separately. I can use either two or four capacitors in series. I bought a separate control board and DC-DC 20A. Order is still in transit. I am planning to charge capacitors current  up to 10A. I have not yet decided whether it is necessary to disconnect the charge of the capacitors during welding. If two capacitors are enough, then I plan to use such a balancer circuit. Attached the diagram. The Chinese do not put up any protection. There are many reviews about the combustion of transistors. Therefore, I want to make a current limitation 1200A.

I am using a China made spot welder which utilized 3000F x 2 series (2.8V) capacitor, works great with 0.15 mm thick nickel strip with only 1/3 of the setting.

[kuna]

I am using a China made spot welder which utilized 3000F x 2 series (2.8V) capacitor, works great with 0.15 mm thick nickel strip with only 1/3 of the setting.

Can You share a link/photo?

[pcm81]

Still have the kWeld, still going strong, still loving it.

One additional function i found for it is light structural welding, basically welding small steel wires, like 24 awg and stainless steel strips to hold things together. Would be allot easier to do with longer leads... Are there any plans to bump up the back feed dissipation circuitry to allow for longer cable length and still maintain 1000A current? K weld seems like a really good controller unit even for a "light commercial duty" welder.

Also, anyone know if they make "welding" pliers that basically have 2 sides isolated from each-other to be able to grab a set of twisted wires and zap them across to form a weld?

[tatus1969]

Still have the kWeld, still going strong, still loving it.

Happy to hear that :-)

bump up the back feed dissipation circuitry to allow for longer cable length and still maintain 1000A current?

1000A would allow more than 3 meters (total) already, would you really need more?

Also, anyone know if they make "welding" pliers that basically have 2 sides isolated from each-other to be able to grab a set of twisted wires and zap them across to form a weld?

Just googling "spot welding pliers" gives me lots of results - these do exist.

[oasis2020]

Great idea!
It's just that there are already many similar products, and the price is very cheap.
If "Kweld" makes a little concession in terms of price, I believe more people will choose it.
In addition, the purchase channel of the product is not perfect. Especially for some countries with strict regulations, the current payment method does not support potential users to place orders.
Thanks!

[tatus1969]

thanks oasis,

I've chosen to not make concessions with regards to performance, stability and usability (repeatability of welds). Also I'm not making concessions with regards to production quality, all my electronics are manufactured in Germany. All this leads to a price that differs from "similar products".

Regarding payment, we offer Paypal and credit cards. What would you suggest in addition?

[oasis2020]

Thank you for your reply, tatus1969.
Yes, there are also netizens in China who have successfully imitated them, but they have not been sold.
But I think your product is more attractive, and it is.
AliPay is more suitable for Chinese users if possible.
Hope your product has more users, because it's really cool!

BTW, if you cooperate with Chinese PCB manufacturers to localize the production of such kits and sell them directly on Chinese online platforms to reduce costs, there may be many potential players.
Of course, this is just a personal suggestion, sorry. 

[tatus1969]

Happy New Year! :-)

I have some news to spread: I am working on a new device "kWeldPro". Parts are already piling up here (chip crisis means that you need to buy a part at the moment you are putting it into your schematics...), and I should have first prototypes by mid of this year. Some key specs:

-   ready to use desktop unit with AC input
-   supports welding copper (3000 amps minimum)
-   450W power supply (200 joule pulse, once per second, at device output terminal)
-   water cooled electrode system (option)
-   pneumatic actuator (option)
-   4.3'' touch screen
-   USB, RS232, PLC interface, dual trigger
-   folded steel enclosure
-   price tag around 1000€ (base unit, probes and power supply will be extra)

Cheers Frank

[tatus1969]

Wow, that's a lot more copper 

[tatus1969]

[Kjelt]

Wow, that's a lot more copper 

Now too bad you can't get that copper thickness from your pcb manufacturer 

[Headhoncho]

So I have a kWeld and it works great for battery spot welding. Do you think your kWeld Pro could do capacitive spot welding of threaded studs.

The current looks very similar to conventional spot welding but the time is much longer

https://truweldstudwelding.com/technical-info/time-amps-stud-diameter/

https://www.spotweldingconsultants.com/capacitive-discharge-welders/single-pulse-ins.htm

https://www.aliexpress.us/item/3256804080074555.html?pdp_npi=2%40dis%21USD%21US%20%2445.83%21%2436.66%21%21%21%21%21%40210323a016763495055144923e9e11%2112000028573017741%21btf&_t=pvid%3A10030c57-825e-496a-827a-8bfb586fb522&afTraceInfo=1005004266389307__pc__pcBridgePPC__xxxxxx__1676349505&spm=a2g0o.ppclist.product.mainProduct&gatewayAdapt=glo2usa&_randl_shipto=US

I think this would be a neat expansion of your machines capability.

[tatus1969]

As Hobbyking is often out of stock on my recommended Lipos, I've bought and tested a few more models. I can recommend these two:
https://hobbyking.com/de_de/turnigy-nano-tech-plus-5000mah-3s-70c-lipo-pack-w-xt90.html (calibrates at 1570 amps when fully charged)
https://hobbyking.com/de_de/graphene-5000mah-3s-75c.html (calibrates at 1520 amps when fully charged)

Unfortunately, as of writing this, also these have gotten out of stock... My order was just a month ago.

[tatus1969]

Do you think your kWeld Pro could do capacitive spot welding of threaded studs.

The current looks very similar to conventional spot welding but the time is much longer
...
I think this would be a neat expansion of your machines capability.

That should work indeed, I'll give this a try! I'd estimate that 5/8 diameter is probably the limit, with 0.7 seconds at 1400 amps.

[meln1k]

Just ordered a Kweld and excited about building some li-ion packs. Do you think it is a decent battery to use with it? https://www.modellbau-bochum.de/Gens-Ace-15000mAh-111V-100C-3S2P-Lipo-Akku-EC5-Bashing-Series-EC-5

[tatus1969]

Just ordered a Kweld and excited about building some li-ion packs. Do you think it is a decent battery to use with it? https://www.modellbau-bochum.de/Gens-Ace-15000mAh-111V-100C-3S2P-Lipo-Akku-EC5-Bashing-Series-EC-5

I think that this model is too strong. It has 3x the recommended capacity and will likely have a too low internal resistance. The result will be too much current, putting the welder at risk.

[Dreddi]

I've got my Kweld put together and I've been able to make two small 3 cell packs with it and its fantastic. I went to use it the other day and it does a normal power up cycle, beep, then shut off and start an endless boot loop. If I let it sit for 10 min or so unpowered, it will stay on for a few seconds before it shuts down and start looping. If I'm quick enough in those few seconds I can get a pulse out of it before it start the loop. Different power supplies don't make any difference. It was connected to the KCap but even when connected directly to a battery or lab power supply it cycles. Only thing I've been able to confirm is the 3.3v cycles along with everything else.

I'm not sure if anyone else has run into this but I can't find anything via a search that is even remotely similar. I've sent a tech request to the Kweld contact but I've got no response.

[tatus1969]

I've got my Kweld put together and I've been able to make two small 3 cell packs with it and its fantastic. I went to use it the other day and it does a normal power up cycle, beep, then shut off and start an endless boot loop. If I let it sit for 10 min or so unpowered, it will stay on for a few seconds before it shuts down and start looping. If I'm quick enough in those few seconds I can get a pulse out of it before it start the loop. Different power supplies don't make any difference. It was connected to the KCap but even when connected directly to a battery or lab power supply it cycles. Only thing I've been able to confirm is the 3.3v cycles along with everything else.

I'm not sure if anyone else has run into this but I can't find anything via a search that is even remotely similar. I've sent a tech request to the Kweld contact but I've got no response.

Just to double check: even when using a bench power supply set to 12V / 1A, then it cycles? If so, then please email us at support@keenlab.de and we'll arrange a replacement. Mention your order number.
EDIT. didn't read fully... I'll talk with my supporter to make sure that it gets handled! But I need your name or order number to relate.

[mrpackethead]

I was just reading this thread from its early days, and found some schematic diagrams of what no doubt were early versions..

I was just trying to udnerstand the basic operation of the device..        I was able to see that a pulse gets generated that will turn the Fets on for some fixed period of time ( unless its retriggered ).    In the notes, it talks about constant energy..    what is the Microprocessor measuring and controlling to do this?..   I coudl see what i assume are analog inputs back to the microprocesor across the output..      Are you able to calculate the output energy, from this?

I do like the idea of your Pro machine..   I have a project to build that will need to do many thousands of cells.

[p.larner]

Its the lack of power from the mosfet driver that kills the transistors ,this is caused by voltage sag when welding,this causes the fets to work in linear mode(BAD),just fit a 470uf cap like shown on yt vids,after that they work well,a double pulse would be good for thicker nickel strip tho.