kWeld - "Next level" DIY battery spot welder

Batteries, Chargers, and Battery Management Systems.
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Re: kWeld - "Next level" DIY battery spot welder

Post by ossivirt » Jan 21 2020 3:37am

Qachi wrote:
Jan 21 2020 3:02am
Silly question but has anyone made up their own supply pack for their kweld using 18650s?
Will likely use a ~65AH car battery most of the time but it would be great to use them for a more portable setup.

On another note, drew this electrode holder up for anyone that may find it useful, shaped to be easily held, one piece and no exposed metal
https://www.thingiverse.com/thing:4117601
Hb powerwall on YouTube used his 18650 powerwall modules that are something like 100p laptop cells.. He also had similar electrode holder but that design has problem that its difficult to keep pressure equal between tips. That can cause sparks and problems..

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

Post by tatus1969 » Jan 22 2020 5:17am

Compoundbike wrote:
Jan 20 2020 2:13pm
I have some problems with my K-Weld. It stopped making welds.. it sparks but the weld is not there.
I checked the battery, calibrated again and again.. however it doesnt weld, any known issues what i can look for ?
That's not much info to diagnose :wink: Can you post all the info that the welder displays after calibration OPEN and SHORT, and after a welding attempt? When you calibrate, please make sure to have clean electrodes for the SHORT step (use fine sand paper to clean them), push the tips together hard, and make sure that you don't get any sparks at all.
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Re: kWeld - "Next level" DIY battery spot welder

Post by Compoundbike » Jan 22 2020 12:30pm

Ok i will check out at the weekend, when im in my Workshop, thank you.

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

Post by tatus1969 » Feb 17 2020 3:19am

I got notified about an ebay auction of 800x BCAP0650P (new unopened, dated 2007, mix of laser weldable and threaded posts), tempted to purchase them. Anyone interested in these? I'd test them and sell for 6€ a piece.
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Re: kWeld - "Next level" DIY battery spot welder

Post by 999zip999 » Feb 19 2020 3:58pm

You have a picture or link.

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

Post by flippy » Feb 20 2020 1:47am

tatus1969 wrote:
Feb 17 2020 3:19am
I got notified about an ebay auction of 800x BCAP0650P (new unopened, dated 2007, mix of laser weldable and threaded posts), tempted to purchase them. Anyone interested in these? I'd test them and sell for 6€ a piece.
i would buy a dozen
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Feb 26 2020 1:19pm

The Maxwell caps arrived last week, I have got roughly 800 of them and have put them up in the shop: https://www.keenlab.de/index.php/product/bcap0650/

I am currently doing measurements with them, but so far they appear to be in perfect condition. Measured internal resistance is approximately 0.5 milliohms (!) at 50A test current, which is quite a bit lower than their rated "initial max" of 0.8 mR. Scope screenshots and my setup attached to the post. Capacitance is spot on, leakage current is ongoing (I need to wait a few hours to allow the voltage settle)

Very important: this is the laser weldable variant, which either needs a bit of creativity or a decent welder to attach bus bars or cables to them. Andrew from hiketech (my AU reseller) plans to do tests with his TIG welder, but if you are fine with this hardcore DIY route then a few of them in series (4S should be optimal) would make up a very decent pulse power supply for kWeld. Or, some other kind of project that needs lots of current - the combined short circuit current of all ~ 800 cells that I have here is 2,720,000 amperes 8) 8) 8) 8)
bcap0650.jpg
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Re: kWeld - "Next level" DIY battery spot welder

Post by flippy » Feb 26 2020 2:38pm

tatus1969 wrote:
Feb 26 2020 1:19pm
Very important: this is the laser weldable variant, which either needs a bit of creativity or a decent welder to attach bus bars or cables to them.
if only there was some way to spot weld tabs on these things.... :roll: :mrgreen:
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Re: kWeld - "Next level" DIY battery spot welder

Post by Taswegian » Feb 27 2020 3:53am

The shop only appears to have the Kcap that comes prepopulated with 6x BCAP0310, wasn't there previously a board-only version for people supplying their own caps?

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

Post by flippy » Feb 27 2020 6:26am

Taswegian wrote:
Feb 27 2020 3:53am
The shop only appears to have the Kcap that comes prepopulated with 6x BCAP0310, wasn't there previously a board-only version for people supplying their own caps?
these dont fit.
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Feb 28 2020 4:41am

Taswegian wrote:
Feb 27 2020 3:53am
The shop only appears to have the Kcap that comes prepopulated with 6x BCAP0310, wasn't there previously a board-only version for people supplying their own caps?
I've dropped that from my shop because the price that I got from my EMS was too high (they'd charge 30€ just for the SMD soldered board). With my markup on that, the end price would have been prohibitive.
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Re: kWeld - "Next level" DIY battery spot welder

Post by eee291 » Feb 28 2020 7:03am

JLC PCB to the rescue :lol:

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

Post by tatus1969 » Feb 28 2020 8:26am

eee291 wrote:
Feb 28 2020 7:03am
JLC PCB to the rescue :lol:
They don't have the quality that I am asking for... And I have gone through their price calculator once for a smaller project. Not as cheap as you might think, for example they add USD2500 project cost upfront. I had been using Elecrow at the beginning, and actually moved because of that reason. The German EMS turned out to be cheaper than them.
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Re: kWeld - "Next level" DIY battery spot welder

Post by eikido » Mar 23 2020 4:39am

tatus1969 wrote:
Nov 18 2019 9:06am
bobmutch wrote:
Nov 16 2019 10:43pm
tatus1969 wrote:
Nov 05 2019 5:40am
tatus1969
A couple questions to tatus1969:

1. With the kweld the adjustment for different welds is in energy J. I'm just wondering if there will be a difference in the weld energy used in each weld when your battery is fully charged and when the battery is close to the LVC? or will the setting of 20J delivery the same energy from the first weld when the battery is fully charged to the last weld when the battery is as discharged as the system allows?

2. When you change from an approved LiPo battery to an approved SLA battery will the same 20J deliver the same energy to each weld with the two different batteries?

Bob.
Just like eee291 describes. But this is only true when the pulse duration is small in general. If current is too low, then the require pulse duration grows and more and more heat can travel away from the welding spot, causing it to cool down. That prevents the heat from staying concentrated and will eventually result in poor welds.
I came to read this thread just to look for this question and you answered it.
But i would like to know what pulse you and the rest of you find is acceptable (for let's say 0.15 mm nickel)? The longer the pulse=the lower burst current the battery provide.
Would you say, the higher the current the lower the pulse is better?

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

Post by tatus1969 » Mar 24 2020 4:55am

quick update: still haven't received the kCaps yet, since the manufacturer realized a problem with wave soldering the capacitors: the conveyor belt is slanted, causing the caps to tilt. Solving this with a clamp that will sit on top of them. New expected arrival April 3.

And I want to share a new video with you, from a fellow guy in New Zealand: https://youtu.be/DX1U3UnCej0
I'm very impressed by his video, it is such good that it can even replace my kWeld assembly document.
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Mar 24 2020 4:57am

eikido wrote:
Mar 23 2020 4:39am
I came to read this thread just to look for this question and you answered it.
But i would like to know what pulse you and the rest of you find is acceptable (for let's say 0.15 mm nickel)? The longer the pulse=the lower burst current the battery provide.
Would you say, the higher the current the lower the pulse is better?
It's very simple, the higher the current, the shorter the pulse (actually that is a quadratic equation, as P = I^2 * R), the better. When the pulse duration gets too long (from my experience, I'd say stay below 50ms), then it's no longer spot welding but surface heating.
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Re: kWeld - "Next level" DIY battery spot welder

Post by eikido » Mar 24 2020 6:04am

tatus1969 wrote:
Mar 24 2020 4:57am
eikido wrote:
Mar 23 2020 4:39am
I came to read this thread just to look for this question and you answered it.
But i would like to know what pulse you and the rest of you find is acceptable (for let's say 0.15 mm nickel)? The longer the pulse=the lower burst current the battery provide.
Would you say, the higher the current the lower the pulse is better?
It's very simple, the higher the current, the shorter the pulse (actually that is a quadratic equation, as P = I^2 * R), the better. When the pulse duration gets too long (from my experience, I'd say stay below 50ms), then it's no longer spot welding but surface heating.
Exactly the answer I was looking for. Thank you very much!! =) I've been thinking about this question for months.

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

Post by hamid120 » Mar 25 2020 5:56pm

Have a question regarding calibration.
I use 3s4p spim08hp.
The cable I use from the battery to kweld is 4 awg wire, length of 300mm, so in cable setting I adjusted it to 1.5m. But I get overcurrent during calibration, and 1563a? The voltage of the battery is 11.66v.

Is my cable setting correct, is the solution to use 16awg or 8 awg wire from battery to kweld?

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

Post by tatus1969 » Mar 26 2020 5:06am

hamid120 wrote:
Mar 25 2020 5:56pm
Have a question regarding calibration.
I use 3s4p spim08hp.
The cable I use from the battery to kweld is 4 awg wire, length of 300mm, so in cable setting I adjusted it to 1.5m. But I get overcurrent during calibration, and 1563a? The voltage of the battery is 11.66v.

Is my cable setting correct, is the solution to use 16awg or 8 awg wire from battery to kweld?
Your cable setting is correct, as is the reaction from the unit. That extra cable length increased loop inductance (please see the operating manual section regarding inductive kickback), which requires to lower the maximum allowed current. Only at 1.0m total round-trip, the unit can handle 2000A.

Using thinner gauge wire will probably add the necessary resistance to lower the current below the max, but you a) then have less current to handle thick nickel strips, and b) a new heat problem.

It is essential to keep the wiring as short as possible, so I suggest to reduce the length down to 1m. Current is then best regulated by choosing a good combination of battery voltage and internal resistance. In your case, you might want to test 2s4p, and if that doesn't work (it should!), 3s3p.
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Re: kWeld - "Next level" DIY battery spot welder

Post by hamid120 » Mar 26 2020 7:29am

Thank you very much the help! :)

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

Post by flippy » Mar 26 2020 10:49am

technically you could just set the wire length to 1m or so so it does not error out. but you will probably blow the arse out of the diodes if you use it like that. best is to change the supply side so you stay within spec.
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Re: kWeld - "Next level" DIY battery spot welder

Post by hamid120 » Mar 26 2020 10:39pm

So after disassembling the packs, and making it to 3s3p, I weirdly still get 1800amp? What could be the reason? Could it be that I soldered the lugs for 4 awg, that may make it read wrong?

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

Post by flippy » Mar 27 2020 6:18am

if you have brand new cells fully charged you might get pretty serious amps. that will reduce after a few cycles or just discharge the pack to 4v per cel or something.
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Re: kWeld - "Next level" DIY battery spot welder

Post by tatus1969 » Mar 27 2020 7:40am

1800amp is perfect, as long as the welder doesn't complain about overcurent (provided that you also have reduced the cables to 1m total!)
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Re: kWeld - "Next level" DIY battery spot welder

Post by Vbruun » Mar 29 2020 1:32pm

I am looking into the Maxwell capacitors.

Would it be possible to simply make the series connection by clamping om busbars in and enclosure or is it necessary to weld or something similar?

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