Author Topic: kWeld - "Next level" DIY battery spot welder  (Read 142709 times)

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Offline zucca

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #425 on: October 26, 2017, 01:21:02 pm »
Thanks tatus1969, read everything in 3 hours or so. Understood almost 30% of it.
Just post it in the Buy/Sell when the next batch is ready.

 ;)

EDIT: Just signed up to your newsletter.
EDIT2: You may want to edit your first post in this thread, new people like me will find quickly what the current status is. For example:
https://www.eevblog.com/forum/projects/diy-programmable-dual-channel-bench-psu-0-50v3a/msg589395/#msg589395

Thanks!
« Last Edit: October 26, 2017, 02:18:54 pm by zucca »
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #426 on: October 28, 2017, 09:12:17 am »
edit your first post in this thread
Thanks for your suggestions! I will do this in a few days. I am almost done with ordering 100x rev3 boards, almost everything else has already arrived.

Maybe a little sneak preview: I could again simplify the production process of the electrode system. This is now the fourth iteration, and I am quite happy with that:


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Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #427 on: October 28, 2017, 10:31:42 am »
That is how I intend to make my probes as well. Easily removable, yet low resistance. You have done a very nice job of those probes :)

Fraser
 

Offline Kjelt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #428 on: October 28, 2017, 02:17:45 pm »
Maybe a little sneak preview: I could again simplify the production process of the electrode system. This is now the fourth iteration, and I am quite happy with that:
That looks really good, almost resembles a bullet  ;D Is that brass with a copper electrode ?
In the mean time my project has come to a standstill, I am awaiting the final results of which supercaps I need to succesfully weld the tabs, is there already a final outcome?
And my 45V/70A PSU has a major issues, which I am still trying to solve, it is still open for repair.

But I did do some new stuff, I build a jig that will help me do some other welding operation: weld two tabs together, for which I need a vertical welding jig.
So this is how that looks, I found most parts of that jig in the dumpster a few years ago and now have a good use for it.
The electrodes I got where 7mm copper bars for the staggering price of €1.- a piece at my local ironscrap yard  :-+
On top there is a 6mm thread to mount the weldingwire and the bottom is a 5mm tapped hole for your 5mm electrodes I bought from you with the kit.
« Last Edit: October 28, 2017, 02:19:17 pm by Kjelt »
 

Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #429 on: October 28, 2017, 03:28:30 pm »
At Franks request I just checked the 3D printed case for fit around the kWeld PCB. I have not printed the final top and bottom pieces but the test piece appears to fit the PCB well. Pictures attached.

I am also intending to make some simple re-enforcement 'washers' for the bases of the two fragile pillars. The rings will be glued in place to provide lateral support. The test piece shown here is just that, an ABS pillar with a snug fit thick ABS washer at its base. I have left the build raft in place for now. The washer will be glued in pace with ABS cement or plastic weld.

I do not have the original Sketchup file so cannot edit the original design.

Fraser

 
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #430 on: October 29, 2017, 10:51:15 am »
That looks really good, almost resembles a bullet  ;D Is that brass with a copper electrode ?
Yes, these are 5mm copper rods, crimped to XT150 male "bullets". The electrode holder is CNC machined to fit AWG8 on the other end. Just two crimps to finish everything, one minute of work :-)

In the mean time my project has come to a standstill, I am awaiting the final results of which supercaps I need to succesfully weld the tabs, is there already a final outcome?
And my 45V/70A PSU has a major issues, which I am still trying to solve, it is still open for repair.
After having finished the second kWeld batch, I will go forward with a 2S2P 3S2P BCAP0310-P270-T10 configuration. That has already shown to deliver >1000A in my lab. Your 70A PSU will be perfect for them. The kWeld rev.3 will have an input voltage range from 4V to 30V (SEPIC converter) and will be able to run directly from these capacitors. I have also substantially improved the power switch, I have just made an explicit overload test of the power switch. It is rated at 2000A, and I tested it with 1000 successful pulses at 2200A, followed with 800 pulses at an extreme overload of 2800A (!) before it broke down. Also the inductive kickback handling should be better now, I will test that today.

But I did do some new stuff, I build a jig that will help me do some other welding operation: weld two tabs together, for which I need a vertical welding jig.
So this is how that looks, I found most parts of that jig in the dumpster a few years ago and now have a good use for it.
The electrodes I got where 7mm copper bars for the staggering price of €1.- a piece at my local ironscrap yard  :-+
On top there is a 6mm thread to mount the weldingwire and the bottom is a 5mm tapped hole for your 5mm electrodes I bought from you with the kit.
:-+
« Last Edit: October 30, 2017, 02:06:21 pm by tatus1969 »
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Offline beduino

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #431 on: October 29, 2017, 12:59:23 pm »
I have also substantially improved the power switch, I have just tested it with 1000 pulses at 2200A, followed with 800 pulses at 2800A (!) before it broke down. Also the inductive kickback handling should be better now, I will test that today.
Old school transformer 230VAC -> 2.5V which means at 10A at primary pulse 1000A on secondary few turns of copper pipe with simple SCR based switch on transformer primary to turnoff at zero crossing much more reliable, however copper costs and transformer weightw, anyway some people buy gold for savings, the more copper we have the richer we are and forget about stuff like this-this is good for selling - lower weight etc, but less copper means lower weight means less reliable lower quality.

High quality products might weight while made of pure metals not plastic crap ;)
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #432 on: October 29, 2017, 04:43:09 pm »
Old school transformer 230VAC -> 2.5V which means at 10A at primary pulse 1000A on secondary few turns of copper pipe with simple SCR based switch on transformer primary to turnoff at zero crossing much more reliable, however copper costs and transformer weightw, anyway some people buy gold for savings, the more copper we have the richer we are and forget about stuff like this-this is good for selling - lower weight etc, but less copper means lower weight means less reliable lower quality.
That will only allow to chop the pulse duration into multiples of 10(8.3)ms, which was too much of a drawback for me when starting this. The kWeld has a resolution of 10us and a minimum pulse width of 40us, which gives it the bandwidth to weld 0.3mm nickel strips equally well as thin copper strands.
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Offline Kjelt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #433 on: October 29, 2017, 05:56:00 pm »
After having finished the second kWeld batch, I will go forward with a 2S2P 3S2P BCAP0310-P270-T10 configuration.
Thanks. Where do you get the supercap protection pcb's ? Or did you design them your self ?

Quote
I have also substantially improved the power switch, I have just tested it with 1000 pulses at 2200A, followed with 800 pulses at 2800A (!) before it broke down.

Please remind me, are you talking about the powermosfets on the pcb or something else? What made it break down, overheating? If I only use it once in awhile for ten welds this is not an issue is it?
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #434 on: October 29, 2017, 11:13:34 pm »
Thanks. Where do you get the supercap protection pcb's ? Or did you design them your self ?
I am using them "free air" for now, manually balancing the voltages. I will design a protection PCB soon.

Please remind me, are you talking about the powermosfets on the pcb or something else? What made it break down, overheating? If I only use it once in awhile for ten welds this is not an issue is it?
Yes, it is the MOSFETs blowing up in an extreme overload stress test. Keep in mind that 2800A is 800A above the overcurrent protection (I have disabled it for the test), and power dissipation wise it is twice the maximum (resistive losses are current squared). For the test, I was running the unit directly shorted and had two batteries connected in parallel. This is far from reality, but I wanted to find the limits. Nothing to worry :-)

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Offline beduino

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #435 on: October 30, 2017, 08:32:48 am »
For the test, I was running the unit directly shorted and had two batteries connected in parallel. This is far from reality, but I wanted to find the limits.
I can't see any supercaps there - anyway I do not think they are rated for 1000A or so to use them for discharge at such extreme conditions, but while I haven't seen their specs or maybe plenty of them they are used in parallel . lets say 10 each rated at 100A discharge ?

I've already seen another project some time ago where someone used bulky IGBT to switch currents at range of 1000A at spot welder at he was not able to manage induction spikes which kiled many not cheap IGBTs, so what can I say, good luck  :-BROKE
 

Offline tautech

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #436 on: October 30, 2017, 09:09:16 am »
I've already seen another project some time ago where someone used bulky IGBT to switch currents at range of 1000A at spot welder at he was not able to manage induction spikes which kiled many not cheap IGBTs, so what can I say, good luck  :-BROKE
You need read this thread from the start, all this has been taken care of to reach a commercial product.

It's not at all unreasonable that tatus1969 would want to do destructive tests to push his product to a new level or just make it more robust.
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Offline Kjelt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #437 on: October 30, 2017, 09:46:53 am »
I will design a protection PCB soon.
Great!  :-+ Also hopefully sell them ?

Quote
Yes, it is the MOSFETs blowing up in an extreme overload stress test.
For the test, I was running the unit directly shorted and had two batteries connected in parallel. This is far from reality, but I wanted to find the limits. Nothing to worry :-)
:-+ I think it would be good to explicitly mention this in the start of such posts before potential customers might think there is a liftetime limit or other limitation.
Great to hear that the design is so robust (made in Germany  :-+ )
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #438 on: October 30, 2017, 02:22:54 pm »
I can't see any supercaps there - anyway I do not think they are rated for 1000A or so to use them for discharge at such extreme conditions, but while I haven't seen their specs or maybe plenty of them they are used in parallel . lets say 10 each rated at 100A discharge ?
Maxwell specifies a continuous discharge current of 250A and a short circuit current of 1200A, with a side note "Current possible with short circuit from rated voltage. Do not use as an operating current." They do not specify a maximum pulse current, which leads me to the assumption that these parts are basically thermally limited. I will do a long term test to validate this, but I am very optimistic. They do not show any measurable effect in ESR or capacitance after a few hundred 900A pulses.


Great!  :-+ Also hopefully sell them ?
That's the plan!

:-+ I think it would be good to explicitly mention this in the start of such posts before potential customers might think there is a liftetime limit or other limitation.
Great to hear that the design is so robust (made in Germany  :-+ )
Thanks :-) I noticed this after your post, and have just edited my post above. I am doing destrutive tests because I am preparing for a batch of 100 and do not want to sit here all day repairing units. I didn't mention that I did this destructive test at 4 pulses per second (!) 8)

The last test yesterday was high inductive load at 2200A and it also survived this 1000 times without damage, although I had to reduce the firing rate to once every two seconds to limit heating of the TVS diode. Here is a picture... (The small ugly board left to the kWeld is the new internal 3-40V power supply that was receiving all that inductive spiking, and it keeps all its voltages well within their limits - should be rock stable now.)

« Last Edit: October 30, 2017, 02:24:30 pm by tatus1969 »
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Offline beduino

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #439 on: October 30, 2017, 05:17:54 pm »
I can't see any supercaps there - anyway I do not think they are rated for 1000A or so to use them for discharge at such extreme conditions, but while I haven't seen their specs or maybe plenty of them they are used in parallel . lets say 10 each rated at 100A discharge ?
Maxwell specifies a continuous discharge current of 250A and a short circuit current of 1200A, with a side note "Current possible with short circuit from rated voltage. Do not use as an operating current." They do not specify a maximum pulse current, which leads me to the assumption that these parts are basically thermally limited. I will do a long term test to validate this, but I am very optimistic. They do not show any measurable effect in ESR or capacitance after a few hundred 900A pulses.
We are talking about this Maxwell HC series ultracapacitors? http://www.mouser.com/ds/2/257/Maxwell_HCSeries_DS_1013793-9-1179788.pdfhttp://www.mouser.com/ds/2/257/Maxwell_HCSeries_DS_1013793-9-1179788.pdf

On page 4 in  PDF linked above we have BCAP0150 with short circuit 190A BUT: this is in Safety section, and probably you are reading its datasheet in wrong way, since this rating in this section as short circuit only means that in the case of some hazards one can expect such huge discharge current and for example part of PCB can disapear, BUT tread again side note second part: "Do not use as an operating current." which means... those caps are not designed to make short circuits at regular basis at such huge currents, while probably overheats them and when you look carefully at thermal cycles at higher temperatures you have 1000 pulses or so in comparision to comfort temperature usage at 25*C with 10 years life span.

A few hundred 1000A pules is nothing for spot welder ... at 50Hz AC with transformer based spot welder is is less than ... 20 s (seconds) of welding with adjustable pulse energy based on time offset between zero crossing and choosen delay  :palm:



Could you give us link to datasheet of these upltracaps you are testing? I can't find any Maxwell rated at continous 250A discharge rate....

Bedu.
« Last Edit: October 30, 2017, 05:22:56 pm by beduino »
 

Offline Southerner

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #440 on: October 30, 2017, 05:50:14 pm »
What about using some boostcaps?  Something like these:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G17930
http://www.goldmine-elec-products.com/prodinfo.asp?number=G22499
They look expensive but might work if enough seriesed or one with voltage rating for the lithium battery used.  Another possibility would be the multi farad automotive audio capacitors that used to be so popular for teeth jarring bass automotive audio systems.
 

Offline ovnr

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #441 on: October 30, 2017, 05:51:18 pm »
A few hundred 1000A pules is nothing for spot welder ... at 50Hz AC with transformer based spot welder is is less than ... 20 s (seconds) of welding with adjustable pulse energy based on time offset between zero crossing and choosen delay  :palm:

To be honest: This is a hobbyist-level product. I don't think tatus1969 plans to sell these to battery pack manufacturers. And if you like transformer-based spot welders so much, go buy or build one?

I want something small, reasonably cheap and controllable. Transformer-based options only tick one of those boxes.
 

Offline ovnr

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #442 on: October 30, 2017, 05:54:18 pm »
What about using some boostcaps?  Something like these:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G17930
http://www.goldmine-elec-products.com/prodinfo.asp?number=G22499
They look expensive but might work if enough seriesed or one with voltage rating for the lithium battery used.  Another possibility would be the multi farad automotive audio capacitors that used to be so popular for teeth jarring bass automotive audio systems.

Well, the original design calls for 6x BCAP0310-P270-T10 at $12.17/pop @ Digikey, or $73 total. Since the design is for a 3S2P pack, you'd need at least 3 of the (used!) $45 caps, for a total of $135. Almost twice as much.
 

Offline Kjelt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #443 on: October 30, 2017, 10:19:39 pm »
Could you give us link to datasheet of these upltracaps you are testing? I can't find any Maxwell rated at continous 250A discharge rate....
He is talking about the bcap 0310 which is cheap and does not have to survive years
http://www.mouser.com/ds/2/257/Maxwell_BCSeries_DS_1017105-4-1179684.pdf

If you want more like 2500A buy the 3400:
http://www.mouser.com/ds/2/257/Maxwell_Technologies_k2_2_85v_ds_3000619en_1-1179621.pdf

Maybe, you do not remember what happened about 75 years ago - hopefully, not everything made by Germany was good:
:palm: i remember well since my family had some real tragedies in that period but as you said that was 75 years ago, over and forgotten and that has nothing to do with the life we are living today and the generations that are living today. I find it rvery offensive that you bring something like this up on an electronics forum.
 

Offline Simon

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #444 on: October 30, 2017, 10:37:50 pm »
Great to hear that the design is so robust (made in Germany  :-+ )

Maybe, you do not remember what happened about 75 years ago - hopefully, not everything made by Germany was good:

Polish 303 Squadron - Battle of Britain


"Squadron 303 (Dywizjon 303) RAF No. 303 "Ko?ciuszko" Polish Fighter Squadron (Polish: Warszawski Dywizjon im. Tadeusza Ko?ciuszki) was the highest-scoring allied unit in the Battle of Britain.[1] It was formed in Britain as part of an agreement between the Polish Government in Exile and the United Kingdom. ..."



There is no relevance in that to this discussion, please stay on topic.
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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #445 on: October 31, 2017, 07:35:22 am »
A few hundred 1000A pules is nothing for spot welder ... at 50Hz AC with transformer based spot welder is is less than ... 20 s (seconds) of welding with adjustable pulse energy based on time offset between zero crossing and choosen delay  :palm:

To be honest: This is a hobbyist-level product. I don't think tatus1969 plans to sell these to battery pack manufacturers. And if you like transformer-based spot welders so much, go buy or build one?

I want something small, reasonably cheap and controllable. Transformer-based options only tick one of those boxes.
Or better buy this pcb only https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F282466833886


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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #446 on: November 03, 2017, 06:25:24 pm »
I am happy to announce that the next batch of kWeld is in production. I accept pre-orders through my shop: https://www.kicksurfer.de/index.php/product-category/kspot-welder-kit/  All pre-order products are on sale with a 10% discount until Nov 30!

New major features in revision 3:
• replaceable electrode system with minimum assembly effort
• extended input voltage range from 4V to 30V allowing the use of ultracapacitors without an auxiliary power supply
• improved protection against inductive kickback of both power switch and voltage regulator, tested to survive currents in excess of 2500A
• enhanced user interface featuring a rotary encoder with push button

Cheers
Frank
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Offline Leo Bodnar

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #447 on: November 03, 2017, 06:44:49 pm »

This is one funny looking j-link.  Did Segger change the design recently?
Leo

Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #448 on: November 03, 2017, 06:45:58 pm »
Hi Frank,

Is there any chance of an upgrade kit to add the push button rotary encoder and additional kickback protection to the MK1 unit please. I do not need the broader range regulator though. It would, of course require some reworking of the PCB by me, but that is no problem. New firmware would also be needed but I have your programming cable already.

It would be great to be able to update the Mk1 to at least the essential parts of the Mk2 design.

Fraser
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #449 on: November 03, 2017, 07:01:48 pm »
Is there any chance of an upgrade kit to add the push button rotary encoder and additional kickback protection to the MK1 unit please. I do not need the broader range regulator though. It would, of course require some reworking of the PCB by me, but that is no problem. New firmware would also be needed but I have your programming cable already.
That is possible. Here is a picture of the additional protection elements. All parts are available at Digikey:
SLD8S28A (large 28V TVS, Littelfuse)
SMDJ28A (28V TVS in SMC package, Littelfuse)
2920L030 (resettable PTC fuse, 300mA, Littelfuse)

The first one is new, and it goes in parallel to the MOSFETs. The other two replace the "quick fix" that I recommended before. I didn't like the resistor in the current path, that fuse also adds resistance.

The rotary encoder is not that simple, because it uses new microcontroller pins and has a different footprint. If you still want to do this, the part no. is PEC12R-4220F-S0024 (also Digikey). I have attached the relevant schematic diagram page here as well.
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