kWeld - "Next level" DIY battery spot welder

[Kjelt]

I plan to sell the capacitor balancer board with and without capacitors.

Please sent me a pm if these are for sale in your shop 

[tatus1969]

I plan to sell the capacitor balancer board with and without capacitors.

Please sent me a pm if these are for sale in your shop 

Can I ask you to subscribe to the website newsletter? It's because I'm likely to forget doing that when it's time. I know myself better ;-)

[Kjelt]

I plan to sell the capacitor balancer board with and without capacitors.

Please sent me a pm if these are for sale in your shop 

Can I ask you to subscribe to the website newsletter? It's because I'm likely to forget doing that when it's time. I know myself better ;-)

Done, i think..........
I press the subscribe button but nothing further happens?

[tatus1969]

I have received pictures of this beautiful case from a customer. It is laser cut material from 3mm panels, which should also be more cost effective than 3D printed parts.



I've made his design available here for you to download: https://www.kicksurfer.de/index.php/product/kweld-lasercut-housing/

[arcol]

Bear with me, if it is slightly offtopic question.

I would like to build some battery pack for power tools (different brand, so I want to unify them).
I'm looking for these type of connectors not really important which type I end up with,
only want to have pairs. Please see the attached picture.
 
So I can build adapters. I don't know the proper english term, or I'm really unlucky, but can not find
anywhere (ebay, mouser, lcsc.com).

Can somebody tell me how could I source such connectors?
These is the only obstacle between me and a spot welder...

[anishkgt]

Those seem like some lithium battery pack connectors. I suggest you start another thread for this. You would get more response add more pics mention where this is taken from like what device and what it originally connects to.

[tatus1969]

new stock is coming, and I've just opened for pre-orders at the shop! --> https://www.keenlab.de/index.php/product-category/kspot-welder-kit/

[anishkgt]

Hey frank since your high power designs for this project, thought I’d share this article that I came across

https://www.allaboutcircuits.com/news/how-mosfet-arrays-balance-supercapacitor-cells/?utm_source=All+About+Circuits+Members&utm_campaign=80d6eb1df1-EMAIL_CAMPAIGN_2017_12_22&utm_medium=email&utm_term=0_2565529c4b-80d6eb1df1-272670005/


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[tatus1969]

Hey frank since your high power designs for this project, thought I’d share this article that I came across

[url=https://www.allaboutcircuits.com/news/how-mosfet-arrays-balance-supercapacitor-cells/?utm_source=All+About+Circuits+Members&utm_campaign=80d6eb1df1-EMAIL_CAMPAIGN_2017_12_22&utm_medium=email&utm_term=0_2565529c4b-80d6eb1df1-272670005/]https://www.allaboutcircuits.com/news/how-mosfet-arrays-balance-supercapacitor-cells/?utm_source=All+About+Circuits+Members&utm_campaign=80d6eb1df1-EMAIL_CAMPAIGN_2017_12_22&utm_medium=email&utm_term=0_2565529c4b-80d6eb1df1-272670005/[/URL]


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

That is an interesting idea, they juse use matched MOSFETs with precise gate threshold voltages. The circuit complexity cannot get lower than that.

As I will use the capacitors under extreme conditions, I expect them to start drifting quicker than if they were used for some kind of backup. This is why my balancer is a bit more complex and uses some comparators. It is a kind of intelligent balancing technique that decides which cells to discharge based on the average voltage from the pack. This way it is only reducing voltage of those cells that are a certain delta above the others. The circuit is still cheap because it doesn`t use anything else than jellybean comparators, some MOSFETs and shunt resistors.

[anishkgt]

Good to know.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[tatus1969]

I have received the first batch of laser-cut housing parts for kWeld. Here is a picture of the first build, they will be available in my shop soon. These are much more affordable than 3D printed housings (unless you have a printer yourself), so I stopped the development of those.

[anishkgt]

I would have it colored solid black or a different shade with just two or three holes and a tiny fan for cooling. Adds that pro look to it frank.

Don’t get me wrong but this is kinda childish to me.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[tatus1969]

I would have it colored solid black or a different shade with just two or three holes and a tiny fan for cooling. Adds that pro look to it frank.

Thanks for your suggestion. I think that I will make it available in two colors, transparent and white. But this mainly because acrylic glass is just beautiful (therefore I started with that) but you can see every tiny scratch. I don`t think that the welder needs as fan, as the module does not produce lots of heat. The only part that heats up significantly is the fuse. I have never managed to heat the MOSFETs above ~ 50°C. The weakest parts of the system are the Lipo battery and the electrodes.

[branadic]

Hi all,

I've already ordered the kWeld kit and wait for it to arrive. Nevertheless I'm interested in what is possible with it and do have questions that are worth to discuss here. Some of the questions were already asked and answered by Frank, but I will ask them here again.

Is butt welding possible with kWeld as shown here or what is necessary to make kWeld able to butt weld?



One possible solution is to use a second microcontroller that controls a cinematic as well as kWeld. The foot switch is a simple 3.3V digital input with a 100k pullup and a 1k/1nF low pass filter on the input, as Frank wrote me.

How to spot weld a (resistance) wire with kWeld to a rod or similar?

I've seen the picture on kWeld website and would like to know more about how this has been done. It looks like some electrode has been used.



minute 12 ff.

I think it would be helpful for all of us to share the knowledge and experience with kWeld as well as modifications done to realize specialties.

-branadic-

[anishkgt]

Its all about mastering the weld time and energy. I've made one but they are meant to be used with a MOT (Microwave Oven Transformer). The project is explained here  (https://georgehobby.wordpress.com/2018/01/27/maxweldv2/) Basically a dual pulse spot welder, unlike KWeld. Max weld works on time delay ranging from 0 (being disabled) to 1000ms.


Edit:
Am sure this would be achievable in kWeld as well.

[branadic]

Thanks for your response, even though I hoped that those guys with a kWeld would have shared their experience here.

-branadic-

[tatus1969]

The most recent batch of 150 kWeld's is shipped out, and I have now time to make some progress. Next will be the ultracapacitor module that will be part of the stationery kWeld supply (but can be used for a lot of other purposes, of course :-). The design is finished and ordered, and here are some first pictures.

The specifications are:
- using Maxwell BCAP0310 cells in a 3S2P configuration
- 8.1V / 206F / 6780Ws
- balancing circuit that actually does what it is supposed to: keep the cells balanced within +-50mV (most far-east modules only have overvoltage limiters)
- temperature monitoring and control of optional 120mm fan
- separate input and output terminals
- series diode for charger to protect it from inductive kickback when welding
- dimensions 110x110x47mm (bare module), 120x120x105mm (with fan and standoffs)
- most important: the output current with kWeld is approximately 1000A
- maximum repetition rate (50J pulses) is once every 4 seconds without fan cooling, which can be lowered significantly with a decent fan

I plan to sell them at www.keenlab.de in three different fashions:
- as fully assembled board for 100€ (the module comes without a fan and the needed standoffs)
- as assembled board, but without the capacitors for 25€

If you are interested, then please leave me a message or check out https://www.keenlab.de/index.php/product/kweld-ultracapacitor-module/

[Kjelt]

  on the waitinglist 

[all_repair]

Waiting for assembled board without capacitor here.

[tatus1969]

Thanks guys

[carracing111]

I join the waiting list!

I have a couple of questions:

Kweld is capable of handling 2000A and the set of capacitors only 1000A. Is it possible to use two sets of capacitors in parallel?
I've thought about this to get solder thicker nickel strips or maybe to achieve a faster welding frequency, 4 seconds is a long time! With my current car-audio capacitors (6 in parallel), I perform 1 welding every second approximately.

I have 12 Maxwell BCAP0350 capacitors, would they work with your protection board or is the ESR too high (3.2 mOhms)?

I recently received the welder Kweld. It must be said that it looks impressive! I'm looking forward to trying it! It will work with a pneumatic welding head in the same way that I have running my current Arduino Spot Welder. When I do I will comment on how it works!

I am very satisfied with my current welding system, although I am limited to 0.15mm nickel. I hope to get to weld at least 0.25mm strips with Kweld!

Regards.

[tatus1969]

I join the waiting list!

great 

Kweld is capable of handling 2000A and the set of capacitors only 1000A. Is it possible to use two sets of capacitors in parallel?
I've thought about this to get solder thicker nickel strips or maybe to achieve a faster welding frequency, 4 seconds is a long time! With my current car-audio capacitors (6 in parallel), I perform 1 welding every second approximately.

I've started with conservative numbers while waiting for the PCBs, and I'll make an update as soon as I have them. I've measured around 1200A with my hand-wired mockup, but the PCB will have less thick power tracks (the first attempt will be standard 35um double-sided). 1200A is already enough to weld 0.3mm pure nickel without slots (that needs approximately 90-100J). It is possible to reduce the wiring resistances of the connected welder by using lower gauge wires, which should allow to go up even higher.

The 4-second repetition rate is based on thermal limitations of the capacitors themselves, as they heat up from their own ESR. They have a large thermal mass (time constant is in the order of 5 minutes), which means that you can do much quicker bursts, as long as the charger can keep up with that. The 4-second rate is meant to keep the thermal equilibrium below the maximum. And that is with convection cooling, without a fan. Adding that will improve the situation significantly, which is why I added support for that (hysteretic on-off control to keep it simple). You can safely use supercaps up to their rated voltage, but they don't like high temperatures. (This is information that I got when having had Nesscap engineers visiting us some years ago, especially confirming the first statement. You don't need to have a voltage safety margin.)

I have 12 Maxwell BCAP0350 capacitors, would they work with your protection board or is the ESR too high (3.2 mOhms)?

If you combine enough of them (I'd say 3S3P, maybe 4S2P), then you can overcome their higher ESR. But they have a different pinout and cannot be mounted directly on the kWeld-cap board.

I recently received the welder Kweld. It must be said that it looks impressive! I'm looking forward to trying it! It will work with a pneumatic welding head in the same way that I have running my current Arduino Spot Welder. When I do I will comment on how it works!

Great, I'm curious!

I am very satisfied with my current welding system, although I am limited to 0.15mm nickel. I hope to get to weld at least 0.25mm strips with Kweld!

See above 

[carracing111]

Perfect, thanks for the quick response.

I will order two boards without condensers plus a full board.
I could try 4S3P with my capacitors. I guess I can make some kind of adapter, so that the pins of my capacitors match.

I attach a couple of photos of my current capacitor configuration and with the welding head that will inherit my new Kweld!

If someone is interested in a head like mine, I can send detailed photos, explain how it works and offer a good price.

Regards

[branadic]

If the fully assembled board works as expected I'm in with one complete board, to replace my 12V 17Ah Pb battery.

-branadic-

[tatus1969]

I attach a couple of photos of my current capacitor configuration and with the welding head that will inherit my new Kweld!

That looks very solid, how do you charge the capacitors?

If the fully assembled board works as expected I'm in with one complete board, to replace my 12V 17Ah Pb battery.

The test PCBs will arrive in two days, I'll know very soon.