kWeld - "Next level" DIY battery spot welder

Batteries, Chargers, and Battery Management Systems.
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tatus1969   100 W

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

Post by tatus1969 » Sep 17 2018 4:19am

mk77 wrote:
Sep 16 2018 11:13am
NIce work! a definite improvement - I like the automated feature - wish
I could get it implemented in my dual pulse unit.... anyway....
Couple quick questions:

1. Which PIC/MCU is used? ((not that it matters - just curious))

2. Will cleaning the electrode tips help with the "resistance issue"? I use
a dual pulse welder built from an E.S. thread a few years ago and find keeping
my tips clean of carbon build up really helps with weld-spot quality. I
use tungsten electrodes - here it's called elkonite.

3. Since the kWeld unit (if I understand correctly) measures the weld-point
resistance for each weld, is it possible for it to also calculate the
required energy to make that weld vs manually setting a number of joules?
Of course, an additional needed parameter would be the type of tab
material/thickness; but it would seem trying to keep a uniform
pressure by hand (and thus bonding contact) on the electrodes
may be compensated by calculating the required energy needed
for a given contact resistance..... or am I trying too hard???
Thanks.
1. No PIC, those are much too slow for this task :-) It is an STM32F103C6T6A.
2. What do you mean with "resistance issue"?
3. kWeld measures the amount of energy (= heat) that is dumped into the weld spot. This improves the weld repeatbility and makes it farily independent from dirt or corrosion on electrode tip / nickel tab / battery. I had the idea to use the measured resistance to estimate the spot temperature, but the data curves actually don't allow that (both shape and spread). I dropped this quickly because that would probably have had a negative impact on repeatability.
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Re: kWeld - "Next level" DIY battery spot welder

Post by mk77 » Sep 17 2018 1:00pm

tatus1969 wrote:
Sep 17 2018 4:19am
2. What do you mean with "resistance issue"?
I've read/re-read the posts which prompted this question. Some users were reporting lower (~900A) than desired target
current levels (~1400A) and now seems more of a battery capacity issue than anything else. As you say the observed
results dictate the parameters....
tatus1969 wrote:
Sep 17 2018 4:19am
3. kWeld measures the amount of energy (= heat) that is dumped into the weld spot. This improves the weld repeatbility ...
Are these measurements used, or carried forward, to help in determining the pulse width of the next weld?

I am so enamored with the automatic feature than I am starting to dream up a delay switched, probe measurement
circuit to install in my welder.... man that's sweet.

edit: for proper reference language :oops: .
Electrons are fun to play with... there are so many of them and they are SO responsive!

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tatus1969   100 W

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

Post by tatus1969 » Sep 18 2018 4:35am

mk77 wrote:
Sep 17 2018 1:00pm
tatus1969 wrote:
Sep 17 2018 4:19am
3. kWeld measures the amount of energy (= heat) that is dumped into the weld spot. This improves the weld repeatbility ...
Are these measurements used, or carried forward, to help in determining the pulse width of the next weld?
You're almost there :wink: The unit does that during the pulse, to determine its correct duration. The firmware in fact does not have a pulse timer at all (apart from a timeout).
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Re: kWeld - "Next level" DIY battery spot welder

Post by ichiban » Sep 27 2018 12:03pm

Dear Frank (tatus1969),

I have some questions for you re kWeld system for I want to start building my own pack(s) :

new thread :
kWeld Spot Welder Questions 2018.09.27
viewtopic.php?f=14&t=96566

Any comments from anyone will be appreciated.

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

Post by eee291 » Sep 28 2018 10:31am

Hey guys, does anyone know what that (pfg 7HIHC) smd component is exactly? My guess it's a TVS diode.

Mine broke and is causing a REMOVE SHORT error.

I don't exactly know what to Google so some help would be appreciated.

I barely made 5 welds with this thing.

I also have the necessary tools to resolder it myself.

http://imgur.com/tFCBVOc
http://imgur.com/GF76HJQ
http://imgur.com/y8sS6EU

I'm guessing it broke when I tried to weld a .3mm nickel strip to a 18650 Cell that was smeared with some flux. It didn't weld to the cell, but a make quite a spark.

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

Post by tatus1969 » Oct 01 2018 10:29am

eee291 wrote:
Sep 28 2018 10:31am
Hey guys, does anyone know what that (pfg 7HIHC) smd component is exactly? My guess it's a TVS diode.

Mine broke and is causing a REMOVE SHORT error.

I don't exactly know what to Google so some help would be appreciated.

I barely made 5 welds with this thing.

I also have the necessary tools to resolder it myself.

http://imgur.com/tFCBVOc
http://imgur.com/GF76HJQ
http://imgur.com/y8sS6EU

I'm guessing it broke when I tried to weld a .3mm nickel strip to a 18650 Cell that was smeared with some flux. It didn't weld to the cell, but a make quite a spark.
That is a Littelfuse SMDJ28. Can you please post a picture of your power cabling? And what power source are you using? I'm interested to find out why the TVS diode failed.
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Re: kWeld - "Next level" DIY battery spot welder

Post by eee291 » Oct 01 2018 2:14pm

https://imgur.com/a/D4hTUf9

The Battery is a Lifepo4 4S1P 21Ah 5C pack. The wires are about 4cm each.

Like I said it worked fine when I was welding 0.1mm Nickel at 10J. My brother had a pack that he bought from tumich, and one of the cells got badly damaged during shipping.
I decided to buy one cell from nkon and my plan was to solder it at first. So I added some flux to the cell, but I couldn't find my Iron.

I thought: 'Perfect time to use the new spot welder'.

So I set the power to 50J and when I tried to weld it a huge spark with smoke occurred right at the cell since it was still covered in flux. And that is how I fried the welder.

Also, it seems that Digikey and Mouser currently don't have this diode stocked. Is there a chance that you have one? I can only find some from China, and those have a slightly different part nr. SMDJ28CA

Here is a link:https://lcsc.com/product-detail/Others_ ... 24072.html

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

Post by tatus1969 » Oct 03 2018 4:25am

eee291 wrote:
Oct 01 2018 2:14pm
So I set the power to 50J and when I tried to weld it a huge spark with smoke occurred right at the cell since it was still covered in flux. And that is how I fried the welder.
You cannot fry the welder from bad contact to the weld spot and the resulting sparks, all what happens then is that you get excessive electrode wear. If the diode breaks, then this is either caused by a production defect, or by a too high inductive kickback energy. The latter energy level only depends on the flowing current and the total length of the power wires (counterintuitively, it does not depend on the weld pulse energy). This is why I asked for the type of battery (determining the current level) and the power wiring (determining the inductance). As you wrote in your other email, you are not using extended cable lengths. This means that inductive kickback is withing acceptable limits, because the welder has an integrated overcurrent protection that didn't trip. This means that this is a production defect, and I'll be happy to send you a replacement diode, or repair the unit if you send it back to me.
eee291 wrote:
Oct 01 2018 2:14pm
Also, it seems that Digikey and Mouser currently don't have this diode stocked. Is there a chance that you have one? I can only find some from China, and those have a slightly different part nr. SMDJ28CA
Here is a link:https://lcsc.com/product-detail/Others_ ... 24072.html
That is a bidirectional diode, but you need the unidirectional one for the welder. Digikey shows me stock for this one : https://www.digikey.de/product-detail/d ... ND/2095367
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Oct 09 2018 3:44am

Another video from a customer, if you like to support me please share: https://www.youtube.com/watch?v=Z0j17LVNm3s
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Re: kWeld - "Next level" DIY battery spot welder

Post by eee291 » Oct 09 2018 5:01am

Thanks for the replacement Diode, everything is working again.

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

Post by kocetoMR » Oct 29 2018 1:13pm

kWeld Chinese copy :shock:
https://youtu.be/vOf8Vaf_UMg
have good welding pen
FB_IMG_1540717468678.jpg
spot welder pen

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

Post by tatus1969 » Nov 25 2018 5:35am

kocetoMR wrote:
Oct 29 2018 1:13pm
kWeld Chinese copy :shock:
https://youtu.be/vOf8Vaf_UMg
He copied my mechanical setup, but it doesn't show what that thing is capable of. And I don't see kWeld's benefits: a) energy metering, b) production quality c) reliability.
kocetoMR wrote:
Oct 29 2018 1:13pm
have good welding pen
FB_IMG_1540717468678.jpg
I have tested a similar one, they are not up to the task for kWeld. You can use them as a plasma cigarette lighter ;-)
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Nov 25 2018 6:08am

I've made finally found time to redesign the charger module for the supercapacitor / kCap. (https://endless-sphere.com/forums/viewt ... 0#p1323810 - it's a shame but I had to go back 12 pages in this thread.)

I have just ordered components and boards to make test builds, and if I don't find any new mistakes I will run a first production batch.

The solution is very powerful and charges the ultracapacitor module with 70A, which allows for a very high welding rate. This might be overdone (and overpriced) for people who only use the welder casually, and prefer to use a weaker charger and accept longer recharge time. Therefore I'm thinking to split this into three different variants:
a) (65€) full power version with 70A (peak) output current. You need a specific HP server supply to power it (~20€ used at ebay)
b) (41€) low-cost version with reduced 35A (peak) output current, and without mating connector for the HP supply. This model is to be used with a standard 12V PSU.
c) (17€) optional heat sink kit. This is not included above, and allows a much higher continuous current.

I have to take measurements with the final design, but I think that the heat sinks won't be necessary for operation with kCap, as the average current draw is much lower than 70A even with intense high-energy welding.

Guys, please let me know what you think about it.
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Re: kWeld - "Next level" DIY battery spot welder

Post by spinningmagnets » Nov 25 2018 1:02pm

Frank and I came up with two slightly different designs for electrodes, but they both follow the same design principles. You must use thick copper, and any connection must have a solid copper-to-copper connection. I'm not saying that my electrodes are best, or that Franks are, but lets take a look at those electrodes from China.
kWeld13.png
B
kWeld13.png (126.17 KiB) Viewed 1707 times
The joint at "A" appears to have a silvery connection pressed against the copper flat-bar. I have used Cembre connectors that are pure annealed copper, but they have a thin plating of zinc to eliminate any corrosion and oxidation, so I will assume the connection at "A" is copper to copper. (The bolts appear to be brass, they can be steel which is cheaper and stronger, because the connecting bolt doesn't really perform any of the conductivity of the current)

At "B", the blocks that hold the electrode tips are clearly brass, which is common. Copper is soft, and difficult to drill to any appreciable depth. Brass is copper with 25% added zinc. It has roughly 28% the conductivity of copper, so it has a 3-1/2 times the resistance of copper. It does conduct electricity, but it will be much hotter than the copper parts of the system.

If you are thinking about using thicker copper conductors to reduce the heat from welding, be aware that any brass parts will be 3 times hotter. When copper is out in the weather, corrosion is a serious issue, but indoors it is not a problem. Copper may turn a little brown instead of bright reddish, but the conductivity of a solid connection is still MUCH better than brass.

The electrode tip holders that frank and I have used is C14500 "Tellurium" copper. It has 93% of the conductivity of pure copper (so they run cooler) but they have a tiny amount of alloy that makes them easy to machine/drill. I approve of cylindrical electrode tips (the replaceable part) because we can find those in copper, tungsten, and carbon.
kWeld10.jpg
A
kWeld10.jpg (130.03 KiB) Viewed 1705 times
kWeldHolder1.png
C
kWeldHolder1.png (951.76 KiB) Viewed 1705 times

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

Post by Megavvolt » Nov 26 2018 6:10am

tatus1969 wrote:
Nov 25 2018 6:08am
a) (65€) full power version with 70A (peak) output current. You need a specific HP server supply to power it (~20€ used at ebay)
b) (41€) low-cost version with reduced 35A (peak) output current, and without mating connector for the HP supply. This model is to be used with a standard 12V PSU.
c) (17€) optional heat sink kit. This is not included above, and allows a much higher continuous current.
I'd go with a)
Got a question though. The 20 euros HP PSU's on eBay look really dirty inside out - are they still ok to buy and use?

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

Post by tatus1969 » Nov 28 2018 11:33am

Megavvolt wrote:
Nov 26 2018 6:10am
Got a question though. The 20 euros HP PSU's on eBay look really dirty inside out - are they still ok to buy and use?
I would only buy them from professional ebay sellers. I bought two HSTNS-PR01 so far, and both were in good nick.
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Re: kWeld - "Next level" DIY battery spot welder

Post by Megavvolt » Nov 28 2018 5:03pm

tatus1969 wrote:
Nov 28 2018 11:33am
Megavvolt wrote:
Nov 26 2018 6:10am
Got a question though. The 20 euros HP PSU's on eBay look really dirty inside out - are they still ok to buy and use?
I would only buy them from professional ebay sellers. I bought two HSTNS-PR01 so far, and both were in good nick.
Could you post a link please?
P.S. Of course if I get a dirty one I won't hold you responsible. :D It's probably just my bad luck.

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

Post by tatus1969 » Dec 01 2018 6:10am

Megavvolt wrote:
Nov 28 2018 5:03pm
tatus1969 wrote:
Nov 28 2018 11:33am
Megavvolt wrote:
Nov 26 2018 6:10am
Got a question though. The 20 euros HP PSU's on eBay look really dirty inside out - are they still ok to buy and use?
I would only buy them from professional ebay sellers. I bought two HSTNS-PR01 so far, and both were in good nick.
Could you post a link please?
P.S. Of course if I get a dirty one I won't hold you responsible. :D It's probably just my bad luck.
This is ebay in Germany, which wouldn't probably make much sense. I just typed HSTNS-PR01 / used, and get 5 local plus 15 international results. https://www.ebay.de/sch/i.html?_from=R4 ... c&LH_BIN=1
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Re: kWeld - "Next level" DIY battery spot welder

Post by Megavvolt » Dec 07 2018 11:29am

Thanks!
I ordered this item. I made an offer of 25 euros and the seller accepted it. The PSU is VERY clean, I can see a tiny bit of dust inside but overall it looks like a part that was inserted into the system but never really used.

I will order kWeld+housing kit and will use it with a lipo, till there's a chance to buy a fatter kCap and your HP PSU full power adapter.

P.S. It's probably a stupid question (because it's your business and not mine) but how come you recommend an XT90 terminals battery but the only connectors available at your store are XT150? :)

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

Post by spinningmagnets » Dec 07 2018 4:14pm

The XT150 's have less resistance, and work better.

Edit: XT90's work fine, it's just that the 150's are better, and would run a little cooler.

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

Post by Megavvolt » Dec 07 2018 4:29pm

spinningmagnets wrote:
Dec 07 2018 4:14pm
The XT150 's have less resistance, and work better.
Didn't think about it. :(
I ordered XT90 connectors along with the hobbyking battery recommended at kWeld page.
Should have probably ordered XT150 connectors instead to replace the battery connector...

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

Post by tatus1969 » Dec 10 2018 4:51am

Megavvolt wrote:
Dec 07 2018 4:29pm
spinningmagnets wrote:
Dec 07 2018 4:14pm
The XT150 's have less resistance, and work better.
Didn't think about it. :(
I ordered XT90 connectors along with the hobbyking battery recommended at kWeld page.
Should have probably ordered XT150 connectors instead to replace the battery connector...
It depends on the "intensity" at which you are going to spot weld (joules, repetition rate), the XT90's might limit you a bit more there. Just check temperatures on a regular basis, and also include the battery and its output leads as you don't want that to overheat. Most batteries have "only" 10AWG wires anyway, even the ones with very high current rating. That's as much as a bottleneck as an XT90. I'm still looking for one with 8AWG at an affordable price, and Hobbyking had started advertising one but then drew that back again.
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Re: kWeld - "Next level" DIY battery spot welder

Post by eee291 » Dec 28 2018 10:16am

I have a question for the users here.

I have made about 3000 welds with this thing and am experiencing some accelerated tip wear when comparing it to the other one.
The electrode connected to the B+ fuse has been reshaped twice while the one connected to the MOSFETs looks almost like new in comparison.
I am using a 3S2P 30Ah NMC Battery since it can output ~1800A, unlike the previous Lifepo4 which could only output ~1100A.
Also, the B+ electrode sticks all the time which I guess is causing the accelerated wear but for some reason, the other one doesn't.

Some other details: 35J welds which take about 10-12ms. 0.2mm slotted Nickel strips.
It also gets too hot to touch after 60-80 welds at these settings.

At this rate, I will have to replace the B+ tip every ~5000 welds and the other one maybe every ~20000 welds

Does anyone else experience this or know why this is happening?

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

Post by spinningmagnets » Dec 28 2018 11:41am

Using copper electrodes, and designing the tips to be replaceable is the most cost-effective option.

Expensive Tungsten electrodes would not get soft and stick to the work, and they are well known to industrial spot-welding machines.

However, they would get MUCH hotter than copper tips.

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

Post by 999zip999 » Dec 28 2018 11:46pm

You find a tig welder who has old tips and try one. But the old tips can be recycled so still have value.

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