kWeld - "Next level" DIY battery spot welder

[spinningmagnets]

The kWeld works quite well on 0.20mm nickel. How many amps do you intend to pull from each cell?

 

[eikido]

I'm quiet sure i will be fine with 0.15x7-8mm but if 0.2mm is easy for the kweld, why not go with 0.2mm directly?
I'd probably never hit more than 10amps per cell. I guess i will be somewhere 3-5 amps.
And you never know, all of a sudden I start building batteries for power tools which requires a lot of current.

 

[tatus1969]

why not go with 0.2mm directly?

One good reason: less thick nickel means less required energy, which means less thermal stress for the battery.

 

[eikido]

I have about 50cm 4AWG pure copper cable on the input.
Should i shorten them because of inductance? What is the downside of worse inductance? I'd rather not because of the size of the car battery

What a wonderful piece of welder

 

[tatus1969]

I have about 50cm 4AWG pure copper cable on the input.
Should i shorten them because of inductance? What is the downside of worse inductance? I'd rather not because of the size of the car battery

What a wonderful piece of welder

Thanks 8) I am explaining the theory behind wire inductance in detail in the kWeld operating manual, please have a look in that. In short words, it is inductance (to be precise: the magnetically stored energy in it) that puts stress on the welder's power switch, not current. Longer cables are allowed, but you need to configure kWeld accordingly for continued reliable operation.

 

[flippy]

for the average person you can just do this: induction = magic.

probably true for quite a lot of electrical enginerds as well.

the shorter the cable the better the magic can flow.

 

[tomjasz]

rescinded offer

 

[Headrc]

If you are offering the Kweld for a donation of $50 to a foodbank I will take it ....

 

[flippy]

How does the performance lack exactly? Just curious as i have the latest version. Coming from a malectrics welder is certainly more rubust. But also triple the price ifyou get the kcap upgrade.
Stuff like overheating is solved with a simple fan, just like most welders need, especially the transofrmer based ones need massive airflow. I modded the case to hold 2 small noctua fans so its silent and gets positive airflow across the power components.

 

[eikido]

I have about 50cm 4AWG pure copper cable on the input.
Should i shorten them because of inductance? What is the downside of worse inductance? I'd rather not because of the size of the car battery

What a wonderful piece of welder

Thanks 8) I am explaining the theory behind wire inductance in detail in the kWeld operating manual, please have a look in that. In short words, it is inductance (to be precise: the magnetically stored energy in it) that puts stress on the welder's power switch, not current. Longer cables are allowed, but you need to configure kWeld accordingly for continued reliable operation.

Super! Found it and read it! So what the cable length parameter does is to limit the current in the whole system. Good thing is the calculations are based on the thickness of the cable and my cables are like super thick so i'm extra protected.

Thanks again.

 

[tomjasz]

How does the performance lack exactly? Just curious as i have the latest version. Coming from a malectrics welder is certainly more robust.

I'm not a power user. From here on I'll only be building 10s4p-6p packs. I have a JP and a JP backup. If i'd have waited I'd have added the latest KWeld. I'm just a nOOb when it comes to soldering and flashing electronics. I hate running Windoze on my MAC so updating is a nuisance.

Tatus has been FANTASTIC. I have no bone to pick with his great work. It's my lack of skill. And at nearly 70, and a mild stroke, I'm not a steady hand.

It just seems to spend more for something I don't need seems, well, silly. AND I have several Vruzend kits.

If you are offering the Kweld for a donation of $50 to a foodbank I will take it ....

Got your message. Will dig it out this weekend. Left my PayPal address, and a preferred email address. You can PayPal me Freinds&Family and I provide a receipt for the donation, OR you can provide me a receipt or cancelled check to your local food bank. Shipping would be nominal. I think it's under 13oz and can go First Class with delivery confirmation. Around $4.00

 

[flippy]

Or better: buy the food and bring it to them.

 

[tomjasz]

Or better: buy the food and bring it to them.

Likelystill availableas I don’t include foot switch and probes. Jeebus fellas here want free lunches...

 

[john61ct]

PM sent

 

[frnandu]

I'm getting "REMOVE SHORT" at start, any idea what may cause this? (the electrodes are not touching)...
Been working fine for few months, and now this....

 

[eee291]

https://endless-sphere.com/forums/viewtopic.php?f=14&t=89039&p=1417408&hilit=diode#p1414802

I had the same issue once, diode melted.

 

[frnandu]

my diode seems fine

 

[flippy]

desolder the diode ans see if it goes away. but i would just order new diodes anyway.

dont run it without a diode.

 

[frnandu]

If I disconnect the fuse (from the electrode side) and connect it again it stops giving "REMOVE SHORT" and it welds without problems.
Any other ideas?

 

[flippy]

most likely is that the diode is starting to break down. and is starting to leak current.
wihtout looking at the sensing circuit you migt want to wait for a answer from the designer.

 

[tatus1969]

If I disconnect the fuse (from the electrode side) and connect it again it stops giving "REMOVE SHORT" and it welds without problems.
Any other ideas?

Please do not trigger welding pulses without a replacement in place, this diode is protecting the switching MOSFETs from inductive kickback energy that those cannot handle reliably. If you PM me then I can send you a replacement diode, or I can do that repair for you but this would cause a lot of shipping overhead. If you want to source that diode by yourself: https://www.digikey.com/products/en?keywords=F8157CT-ND Older boards have a different (smaller) diode, the one in the link is beefier and can withstand abuse longer.

There are a few common situations that can cause this diode to fail:
- if you feed external voltage into the electrodes, this can happen when welding your battery, and accidentally touch different poles of that.
- if your power wiring around the welder is more than one meter in total (e.g. you are using long wires to the battery), and you haven't dialed in the extra length through the welder's menu. I explain the reason for this in the welder's user manual, it's a bit hard to explain. The keyword is inductive kickback.

 

[frnandu]

If I disconnect the fuse (from the electrode side) and connect it again it stops giving "REMOVE SHORT" and it welds without problems.
Any other ideas?

Please do not trigger welding pulses without a replacement in place, this diode is protecting the switching MOSFETs from inductive kickback energy that those cannot handle reliably. If you PM me then I can send you a replacement diode, or I can do that repair for you but this would cause a lot of shipping overhead. If you want to source that diode by yourself: https://www.digikey.com/products/en?keywords=F8157CT-ND Older boards have a different (smaller) diode, the one in the link is beefier and can withstand abuse longer.

There are a few common situations that can cause this diode to fail:
- if you feed external voltage into the electrodes, this can happen when welding your battery, and accidentally touch different poles of that.
- if your power wiring around the welder is more than one meter in total (e.g. you are using long wires to the battery), and you haven't dialed in the extra length through the welder's menu. I explain the reason for this in the welder's user manual, it's a bit hard to explain. The keyword is inductive kickback.

Thank you Frank for the advice.
It seems to me that I have the bigger and it doesn't look damaged.





Is this "REMOVE SHORT" error cause only possible if this diode is somehow damaged (even if it looks ok)?
If so, can it be easily replaced with an ordinary soldering iron?
I need to order from you new electrodes, so if indeed I should replace this diode for stopping the error, maybe you can send me a replacement together with the electrodes?

 

[tatus1969]

Is this "REMOVE SHORT" error cause only possible if this diode is somehow damaged (even if it looks ok)?
If so, can it be easily replaced with an ordinary soldering iron?
I need to order from you new electrodes, so if indeed I should replace this diode for stopping the error, maybe you can send me a replacement together with the electrodes?

It is not always easily noticable when these components crack, sometimes the black top only lifts up very slighlty above the large metal tab at the one end. There are other possible reasons for this message, but I now realize that I haven't read your initial post correctly. You say that you had removed and connected the fuse and that it then worked. I somehow had read that you had removed the TVS diode, which is why I gave that warning. This is a completely different situation, and I am thinking about this right now as I haven't had this before... A few questions:
- you actually removed and replaced the fuse while the system was powered from the battery, right?
- are you sure that you have never accidentally touched something on the logic board with one of the electrodes?
- are you sure that you haven't applied external voltage to the electrodes?
- can you once measure the voltage across the electrodes, a) hafter having powering the system, and b) after you have removed+replaced the fuse?

 

[frnandu]

- you actually removed and replaced the fuse while the system was powered from the battery, right?

Yes, while having power from the battery I slightly disconnected the electrode side of the fuse and then connected it again, and the error went way.

- are you sure that you have never accidentally touched something on the logic board with one of the electrodes?
- are you sure that you haven't applied external voltage to the electrodes?

Since this is a shared welder between a few people in my city I cannot say 100% that someone did these or not.

- can you once measure the voltage across the electrodes, a) hafter having powering the system, and b) after you have removed+replaced the fuse?

Sure, I will in the evening measure and write back to you.
Thanks for the support.

 

[eee291]

In that last pic it looks like someone touched the brass with one of the electrodes. :?

If you get it fixed and still plan on lending it to people then I recommend getting a case for the welder.