kWeld - "Next level" DIY battery spot welder

Batteries, Chargers, and Battery Management Systems.
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Silvaticus   100 mW

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

Post by Silvaticus » Aug 27 2021 11:19pm

I agree that they don't owe me anything. That is why I tried to describe the problem as broadly as possible. I have even added resistance symbols for better clarity. I even believe that we are somewhere close to the truth, but this requires an outside opinion.
And I ask you to forgive me for my wording as I'm not a native speaker.

markz   100 GW

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

Post by markz » Aug 28 2021 1:53am

What is your native tongue?
Silvaticus wrote:
Aug 27 2021 11:19pm
And I ask you to forgive me for my wording as I'm not a native speaker.

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Monte   10 mW

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

Post by Monte » Aug 28 2021 2:46pm

Thanks for designing a great welder! Such an improvement to my earlier car battery-solenoid-timer relay DIY welder.

LTO seems to work great as a power source as well. 4S Yinlong 40Ah cells produce 1800 amps at calibration on the stock cabling lengths.
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Cells are not new, with new cells 3 would probably be fine. Also might manage with 3 if I charged these up to full voltage.

john61ct   100 GW

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

Post by john61ct » Aug 28 2021 7:59pm

So what input voltage range do you use with the 4S?

How low would you go with 3S?

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Silvaticus   100 mW

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

Post by Silvaticus » Aug 28 2021 9:29pm

Here are my colleague's welding results.

Due to the lack of complete confidence in the correctness of our calculations, I cannot provide you with the amount of consumed energy in Ws. However, I can say that welding took place at a voltage of 4.0V. Two welding pulses of 1.5ms and 5.0ms duration were used.

There is an assumption that the total energy including losses was 50Ws of which only about 19-24Ws was used to obtain welded joints.

Resistance of an open welding circuit (from electrode to electrode) with open mosfets (Ri + Rs +Rc) is 1.28mΩ.
On the photo is original of Sony Murata VTC6 cells and pure nickel 200μm.

Image Image

IMHO, this is how welding spots should look like. This is already close to the quality obtained with industrial spot welding machines.
Last edited by Silvaticus on Aug 29 2021 4:04pm, edited 1 time in total.

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spinningmagnets   100 GW

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

Post by spinningmagnets » Aug 28 2021 9:47pm

Silvaticus, perhaps your welder deserves it's own thread? I am very interested in the details, if your colleague would be willing to share any info.

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Monte   10 mW

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Re: kWeld -

Post by Monte » Aug 29 2021 1:30am

john61ct wrote:
Aug 28 2021 7:59pm
So what input voltage range do you use with the 4S?

How low would you go with 3S?
4S was at 9V when I tested it. Fully charged would be about 10,4V. 4S voltage range is between 10,4V-8V

3S would work between 7,8-6V.

I tried 2S first, it gave calibration current of slightly over 1000A, so would also work if I lowered the 800A min current value on the welder. Not optimal though.

These are also the worst cells from 30 I ordered last December, with the other 26 being in a pack already.

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

Post by vanturion » Aug 31 2021 7:36pm

Looking for some advice on power source configuration.

I have 2 6V 225ah on hand that I'd like to use with my kWelder. While they're not CCA rated, they are pretty hefty batteries. Is it better to configure them in series or parallel for the welder? Or should I not bother and just use 1?

I also have a standard 6V/12V SLA 6 amp battery charger I can run concurrently while welding which seems like a good idea.

If it helps I'm planning to use the sandwich method with .2mm copper "H"-strips and either .15mm nickel "H"-strips or .15mm nickel-plated steel "H"-strips if the pure nickel doesn't work out. All of these are slotted at the weld areas.

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Silvaticus   100 mW

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

Post by Silvaticus » Aug 31 2021 9:55pm

vanturion wrote:
Aug 31 2021 7:36pm
If it helps I'm planning to use the sandwich method with .2mm copper "H"-strips and either .15mm nickel "H"-strips or .15mm nickel-plated steel "H"-strips if the pure nickel doesn't work out. All of these are slotted at the weld areas.
Doubt this will help you. Frank himself wrote that he could not weld even 100μm of copper.

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

Post by ossivirt » Aug 31 2021 10:50pm

vanturion wrote:
Aug 31 2021 7:36pm
Looking for some advice on power source configuration.

I have 2 6V 225ah on hand that I'd like to use with my kWelder. While they're not CCA rated, they are pretty hefty batteries. Is it better to configure them in series or parallel for the welder? Or should I not bother and just use 1?

I also have a standard 6V/12V SLA 6 amp battery charger I can run concurrently while welding which seems like a good idea.

If it helps I'm planning to use the sandwich method with .2mm copper "H"-strips and either .15mm nickel "H"-strips or .15mm nickel-plated steel "H"-strips if the pure nickel doesn't work out. All of these are slotted at the weld areas.
Series unless you get overcurrent error. Then paralel and if thats no good then just 1. You also might have to get thinner copper or thinner steel strips if you are not able to get good welds. 0.2 copper is just so hard to weld. You need weld current close to kweld max current just to have chance..

vanturion   10 W

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

Post by vanturion » Sep 01 2021 12:50am

Silvaticus wrote:
Aug 31 2021 9:55pm
Doubt this will help you. Frank himself wrote that he could not weld even 100μm of copper.
srapy's post and spinningmagnet's last link on the Copper/nickel sandwich thread gives me some hope it'll work out. That and it doesn't look like they used slotted copper either. Crossing my fingers..
ossivirt wrote:
Aug 31 2021 10:50pm
Series unless you get overcurrent error...
OK - it won't be hard to reconfigure either way, but I'll start like you say unless I hear otherwise.

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Silvaticus   100 mW

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

Post by Silvaticus » Sep 01 2021 3:37am

vanturion wrote:
Sep 01 2021 12:50am
srapy's post and spinningmagnet's last link on the Copper/nickel sandwich thread gives me some hope it'll work out. That and it doesn't look like they used slotted copper either. Crossing my fingers..
Quite interesting results. I'll have to buy copper and try it. Moreover, we have the opportunity to use almost twice the current of kWeld average with a pulse duration of about 10 ms.
Thanks a lot, I haven't seen this post before.

vanturion   10 W

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

Post by vanturion » Sep 02 2021 5:11pm

Designed a new case more friendly for printing:
kWelder Case.jpg
kWelder Case.jpg (182.61 KiB) Viewed 319 times
Very minimal support material required only at 4X captured nuts features. Just needs a small sight window for fuse.

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Tomblarom   100 mW

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

Post by Tomblarom » Sep 11 2021 7:03am

vanturion wrote:
Sep 02 2021 5:11pm
Designed a new case more friendly for printing
Wow looks great! Would you share it? I'd be interested to try it. :)

Eraser-1   1 mW

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

Post by Eraser-1 » Sep 11 2021 8:09am

Has anybody made a kind of base plate to connect the kCap and the kWeld physically, so that it is one part?

vanturion   10 W

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

Post by vanturion » Sep 11 2021 3:26pm

Tomblarom wrote:
Sep 11 2021 7:03am
vanturion wrote:
Sep 02 2021 5:11pm
Designed a new case more friendly for printing
Wow looks great! Would you share it? I'd be interested to try it. :)
Sure thing, here ya go.

am283721   1 µW

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

Post by am283721 » Sep 13 2021 8:38am

Hey folks, I'm a little embarrassed to post this here, but I was hoping someone could provide some guidance.

I got my kweld recently and was incredibly pleased how well it worked straight out of the box. The plan was to build a case for it to protect the electronics, but I was too distracted by actually using it to build my battery. Then one day while carelessly adjusting a nickel strip, I accidentally touched one of the electrodes to the display unit and zapped it.

The welder doesn't work now. I ordered a new display unit hoping that I only fried the electronics on that, but after installing the new display, the welder still shows no sign of life. When connecting it to my power supply there is no beeping, nothing on the display and the foot pedal does nothing either. I can measure power flowing in various parts of the welder, but I'm not sure how to diagnose which component has failed. Aside from the one pin on the display that has visible damage (the electrode touched the leftmost pin on the display board, see photo), the rest of the components look fine. The bottom of the board did start to feel warm after attaching the power supply.

Any clues as to how to diagnose the issue would be greatly appreciated!

Edit: Did some troubleshooting with a friend. Our best guess is that the MCU is likely cooked. Will either need to get a new one and reprogram it, or order a whole new board.
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LordKitsuna   1 µW

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

Post by LordKitsuna » Sep 14 2021 10:34pm

Hello everyone, I just finished setting up my unit and everything seems to be working but I have some questions about the calibration that the manual does not appear to address. For calibration the manual mentions the resistance rating and also says it should be somewhere between 2.5 and 3. While it does state that a higher number than 3 is not a good thing it does not say if there's anything to be concerned about with a lower number than 2.5. I am currently getting a reading of 2.11. I'm also not entirely certain what the rest of the readings given are for. I assume that "I" is the measured amps which i show as 1816. Which as I understand it is more or less exactly where I want to be since I want to be close to 2,000 but not over. I have included photos of my calibration results could somebody please let me know if everything looks good? I just want to confirm before I go zapping things :)
Image
Image
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Image

Don't worry about the bare board I did get the laser cut housing kit but I wasn't smart enough to get glue ahead of time so I'm waiting for the glue to help protect my welder. Any insight you all can provide would be greatly appreciated!

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tatus1969   1 kW

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

Post by tatus1969 » Sep 15 2021 3:01am

am283721 wrote:
Sep 13 2021 8:38am
The welder doesn't work now.
This forces thousand amps through the logic board, which usually breaks the ground connection (look underneath the board for burn marks). If that has happened, then the board is beyond economic repair as this causes most chips to fail. Also, the MCU is preprogrammed with a custom encrypted bootloader, which I don't have tools for to prepare.
LordKitsuna wrote:
Sep 14 2021 10:34pm
For calibration the manual mentions the resistance rating and also says it should be somewhere between 2.5 and 3. While it does state that a higher number than 3 is not a good thing it does not say if there's anything to be concerned about with a lower number than 2.5. I am currently getting a reading of 2.11.
The new heavy duty probe system has a lower resistance, which I haven't updated in the manual I'm afraid. Your readings are perfect.
Resistance is futile - We Are The Watt.

LordKitsuna   1 µW

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

Post by LordKitsuna » Sep 16 2021 1:58am

tatus1969 wrote:
Sep 15 2021 3:01am
LordKitsuna wrote:
Sep 14 2021 10:34pm
For calibration the manual mentions the resistance rating and also says it should be somewhere between 2.5 and 3. While it does state that a higher number than 3 is not a good thing it does not say if there's anything to be concerned about with a lower number than 2.5. I am currently getting a reading of 2.11.
The new heavy duty probe system has a lower resistance, which I haven't updated in the manual I'm afraid. Your readings are perfect.
Thanks for the confirmation, I ended up going with a heavy duty starter battery it was rated for 900 CCA so I figured that at room temperature it would likely be pretty close to 2k. That might be a lazy way of looking at it but it appears to have worked out for me I'm very close. I have been reading a lot of posts about people trying to weld copper strips I just placed an order for some 0.1mm copper and 0.15 pure nickel looking forward to testing both separate and sandwich.

Although I will need to redo my calibration I did extend the length of the battery cables using some 4AWG wire (just lazily by braiding them into then soldering together with the existing wire) but I assume that using that different size cable screws with the math so I'm going to need to just go get some proper cable at the length I want so I can calibrate it properly

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Tomblarom   100 mW

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

Post by Tomblarom » Sep 16 2021 1:44pm

vanturion wrote:
Sep 11 2021 3:26pm
Sure thing, here ya go.
Very clean in general, just a few ideas I had:
- add a 4,5mm lip around the display to the lid
- add parts to the lid, that compensate for the slots and close the holes/gaps
- fuse window could be as small, as the grid-slots (just for design)
- try to reuse the original 4 stand-offs and screws for installing the lid to the body
- add a version for JST plug for the foot-switch
- add countersinks to make the screw sit flush with the lid

Image Image
Last edited by Tomblarom on Sep 17 2021 4:09am, edited 1 time in total.

vanturion   10 W

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

Post by vanturion » Sep 17 2021 2:11am

Some good ideas in there for sure, and I like your JST mod.

Because I like ya, my discounted design rate is $40/hr, min 3 hours. LMK :wink:

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Tomblarom   100 mW

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

Post by Tomblarom » Sep 17 2021 4:28am

vanturion wrote:
Sep 17 2021 2:11am
Because I like ya, my discounted design rate is $40/hr, min 3 hours. LMK :wink:
LOL :lol: I'll do it myself then hahaha That's not too much work :)

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Merlin   10 MW

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

Post by Merlin » Sep 17 2021 4:29am

dont forget to share for free when your done ;)

LordKitsuna   1 µW

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

Post by LordKitsuna » Sep 18 2021 10:08pm

I thought i posted this but I don't see it so i guess not. Wanted to ask, if i am understanding the math on calibration in the manual correctly it seems like wire size matters. I was going to use 4AWG for the connection to the battery but is the calibration expecting 8AWG in particular? If so is there any kind of conversion calculation i can easily do or is it better to just stick with 8AWG

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