kWeld - "Next level" DIY battery spot welder

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

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

Post by ossivirt » Feb 11 2021 1:49pm

You can go to 100j but that might still not work since the reason why copper is so hard to weld is its ability to conduct the heat away from the weld spot. When you set more joules that basicly means longer pulse time and that means copper has longer time to spread the heat away so at some point you dont get any better weld no matter how many joules you select. But only way to find out is to try..

BTW what is your welding current now?

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

Post by Hummina Shadeeba » Feb 11 2021 2:38pm

ossivirt wrote:
Feb 11 2021 1:49pm
You can go to 100j but that might still not work since the reason why copper is so hard to weld is its ability to conduct the heat away from the weld spot. When you set more joules that basicly means longer pulse time and that means copper has longer time to spread the heat away so at some point you dont get any better weld no matter how many joules you select. But only way to find out is to try..

BTW what is your welding current now?
Welding current 1800amps.

Found some 18650 and it’s the same results with these as the A123s and it’s easy to weld .2mm copper to the top but can’t stick to the bottom even with 90amps.

I imagine a slit could help a lot and looking for a good tool for that. I see hole punchers for leather that might be good
Last edited by Hummina Shadeeba on Feb 11 2021 3:24pm, edited 2 times in total.

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

Post by ossivirt » Feb 11 2021 2:48pm

0.2mm copper is so close to the limit what kweld can weld. With current close to 2000A it is barely possible atleast some cases. Also 0.2mm copper for 18650 cells is usually little bit overkill since 0.1mm or even nickel is enough for most cases.

But please do post results of your work with copper thicknes, joules and current so others will know what is possible!

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

Post by Hummina Shadeeba » Feb 11 2021 3:02pm

Being America I don’t actually find metric stuff just imperial so really I’ve been doing 5mil or .005” sheet which is .127mm. No problem. Good enough and my quest for more copper is over.

I use the included probes and if they start getting stuck I file them to their original rounded point.

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

Post by leffex » Feb 12 2021 12:45pm

So I installed and set up my kweld with transparent housing.

Battery 8.8ah a123 life 6,48v or 3,225v per cell (2s2p setup) (a123, ahr32113 ultra-b orange cells)

Undercurrent at first try with CAL. at 740a and then I get about 840A when pressing down harder and about 2,41mOHM to 2,52mOHM.

Original cables assembled by kweld and additional battery connections at 10AWG and 10cm added for positive and negative from battery side.

I understand I can charge the battery full maybe and I'll get some more current?

What can I weld with these settings and get good results? I need to weld 0,15mm and 0,2 and 0,3 nickel. What A should I be looking at when doing CAL to be able to do each of these sizes?

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

Post by flippy » Feb 12 2021 4:00pm

you need to keep that pack charged up to full and keep it there. so keep a dumb charger on the battery to keep it charged during welds. still, i dont see these cells lasting very long. it would be better to make it a 3S4P at the very minimum if you want to use this setup a lot.
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Re: kWeld - "Next level" DIY battery spot welder

Post by leffex » Feb 12 2021 6:23pm

tatus1969 wrote:
Apr 06 2020 8:27am
It depends on your work piece. 0.1mm nickel doesn't require much current, but 0.3mm nickel much more. kCap is limited to 0.2mm, and for 0.3mm a battery should deliver at least 1400A.
I found the answer earlier in the thread.

flippy. I will try that. Also setup a different battery for 0.3mm when doing more serious series connections.

Thanks for the welder tatus1969 . I think it will work great. Much appreciated!

UPDATE:
So I tested with a fully charged battery and then I tried to weld at 10J and. even 1J but I got error message "undercurrent" so I guess I need to up the battery size to get it working.
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Re: kWeld - "Next level" DIY battery spot welder

Post by Silvaticus » Feb 19 2021 7:39pm

flippy wrote:
Feb 03 2021 7:41am
in NO WAY the bond wire "tric" should be used or copied by DIY people thinking its "the best solution because tesla uses it".
the reason is because tesla uses bond wires is simply because its the fastest and cheapest way to connect a thousands of cells per hour on a single processing station. the simple fact that tesla's wire bonding machines uses a ultrasonic head on itself costs about a solid quarter million a pop should give clue as to why.

even tesla wont use it in their new 4680 batteries...
Tesla uses wire bonding not because it is easy, but because it is easy to reproduce a thousand times with the required length. In addition, each of the segments work as the fuse. Also, it takes about two seconds per sell to attach two wire links.

Where did you get so much confidence about Tesla's plans? Nothing prevents Tesla from using multiple conductors per cell. Or even one or more ribbons. One 2000 x 400 micron ribbon is equivalent to four 500 micron diameter round conductors.

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

Post by Silvaticus » Feb 19 2021 8:01pm

ossivirt wrote:
Feb 11 2021 2:48pm
0.2mm copper is so close to the limit what kweld can weld. With current close to 2000A it is barely possible atleast some cases. Also 0.2mm copper for 18650 cells is usually little bit overkill since 0.1mm or even nickel is enough for most cases.

But please do post results of your work with copper thicknes, joules and current so others will know what is possible!
The electrical conductivity of copper is 5+ times better than nickel.
Even tungsten or molybdenum is better than nickel as a conductor. their conductivity is about 1.6 times better than that of nickel.
If I remember correctly, then for 0.15mm copper needs about 600 J. For 0.2mm copper you need much more. And this despite the fact that mentioned 600 joules require a higher current than 2kA.

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

Post by Hummina Shadeeba » Feb 20 2021 11:50am

Can weld .2mm copper if it’s slotted. Depends on the cell but the 30q 18650 were no problem at 80j.

Can do .1mm copper no problem with much less joules

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

Post by flippy » Feb 20 2021 11:56am

Silvaticus wrote:
Feb 19 2021 7:39pm
flippy wrote:
Feb 03 2021 7:41am
in NO WAY the bond wire "tric" should be used or copied by DIY people thinking its "the best solution because tesla uses it".
the reason is because tesla uses bond wires is simply because its the fastest and cheapest way to connect a thousands of cells per hour on a single processing station. the simple fact that tesla's wire bonding machines uses a ultrasonic head on itself costs about a solid quarter million a pop should give clue as to why.

even tesla wont use it in their new 4680 batteries...
Tesla uses wire bonding not because it is easy, but because it is easy to reproduce a thousand times with the required length. In addition, each of the segments work as the fuse. Also, it takes about two seconds per sell to attach two wire links.

Where did you get so much confidence about Tesla's plans? Nothing prevents Tesla from using multiple conductors per cell. Or even one or more ribbons. One 2000 x 400 micron ribbon is equivalent to four 500 micron diameter round conductors.
you can see the difference from the old S pack to the newer 3/Y pack. bigger cells, thinner connecting sheets (so the welder has less Z axis travel to move between welds) and so on. with the next cells there would be no reason to do wire welds as they can just weld the series plates to the cells as it will help in structual strength. the goal is to use every part of the battery as structural support so they need to weld the plates on the cells directly. it allows for faster processing and greater structural support. in the current packs the cells are basically treated as dead weight so wire bonding was the way to go. in the new pack design they will not do wire welding simply because it wont add any structural support. musk also said he wants to get rid of the wire bonds sooner rather then later a while back.
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Re: kWeld - "Next level" DIY battery spot welder

Post by charlie hepler » Feb 22 2021 9:43am

Hi yaw I just placed an order for the K-weld from Frank on the 12th and can’t wait to get it! Like a kid waiting on Christmas
About how long does it take to a package from Germany to the US? I opted for the 2nd option that gives your package the Air ride vs the water ride but just curious how the COVID thing is changing the shipping times?

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

Post by flippy » Feb 22 2021 9:46am

charlie hepler wrote:
Feb 22 2021 9:43am
Hi yaw I just placed an order for the K-weld from Frank on the 12th and can’t wait to get it! Like a kid waiting on Christmas
About how long does it take to a package from Germany to the US? I opted for the 2nd option that gives your package the Air ride vs the water ride but just curious how the COVID thing is changing the shipping times?
the plane part is pretty fast. the real issue is the shitty postal service used on the US side.
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Re: kWeld - "Next level" DIY battery spot welder

Post by Hummina Shadeeba » Feb 22 2021 2:38pm

charlie hepler wrote:
Feb 22 2021 9:43am
Hi yaw I just placed an order for the K-weld from Frank on the 12th and can’t wait to get it! Like a kid waiting on Christmas
About how long does it take to a package from Germany to the US? I opted for the 2nd option that gives your package the Air ride vs the water ride but just curious how the COVID thing is changing the shipping times?
Just got shipped from Germany and im in California.

What temp is acceptable to be running it?

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

Post by lamaatje » Mar 04 2021 9:55am

Hummina Shadeeba wrote:
Feb 09 2021 8:28pm
I’m saying if i shorten my battery wires too much I get “over current”, but when I lengthen them, to like 2meters including probes now, I have too much inductance to do more than maybe 1200 amps as shows on their posted chart. I want to do more. How?
https://imgur.com/a/qu13QBy
Somehow nobody mentions that inductance depends on loop area. Frank calculates that area from the total cable length which is rather worst case, especially if you twist the wires coming from your source and are able to twist some more on the electrode side the loop area can be reduced considerable. Would be nice if the kweld is able to measure the actual inductive voltage from creating or opening the current loop (or you could use a scope). I do not have the schematics but I suppose there are some components extra to avoid damage to the MOSFET's.

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

Post by Daruben » Mar 04 2021 3:54pm

The electrode wires can be zip tied in parallel to cancel the magnetic field. Same with the battery wires. I don't think they need to be twisted since its DC. This reduces the back EMF. This is safe to do but is not necessary with a stock Kweld. Increasing the diameter of the wire will also lower the inductance, thereby less back EMF. A larger diameter wire will will have less resistance, and therefore less heating. No burnt fingers from heat. With less resistance there will be more current shown when calibrating. More current, within limits of the Kweld will generally produce better welds at less joules. Know what you are doing before changing your setup.

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

Post by Daruben » Mar 04 2021 5:14pm

Hummina Shadeeba wrote:
Feb 09 2021 12:29am
if i shorten my battery wires i get an "overcurrent" when calibrating. i need to add resistance but not inductance somehow. ive gone back and forth adding and cutting trying to find a sweet spot but if i go shorter than maybe a meter and a half ill get the overcurrent and cant weld. from what i read the welder alters the output time period and not the current and the current is fixed when you do the calibration based on the resistance of the whole system.
I recommend you use the standard length cabling and AWG that comes with the Kweld. No longer. If your over current, lowering your kweld input voltage is the best choice. A 12v car battery or 3S lipo voltage should be plenty. Alternatively, but not the better choice, you can use a smaller wire size (same length) on the battery side to increase resistance and lower current.

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

Post by john61ct » Mar 04 2021 7:39pm

A voltage adjustable lab PSU would be better than swapping out batteries, right?

Sorensens can go for cheap on eBay

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Re: kWeld -

Post by Daruben » Mar 04 2021 7:51pm

john61ct wrote:
Mar 04 2021 7:39pm
A voltage adjustable lab PSU would be better than swapping out batteries, right?

Sorensens can go for cheap on eBay
If you are talking about using the supply to charge Kcaps or a supercapacitor, yes that would be ideal for testing different voltages as long as they can charge into a dead short (uncharged capacitor). Most lab power supplies cant supply the huge current alone, and require supercapacitors.

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

Post by charlie hepler » Mar 04 2021 9:25pm

Got my new tool (K-WELD)and put it together today!

Tried to test weld on some .15m Nic and the welds were not good. I increased the Joules from 10 up to 60 doing test welds along the way and never did get good results? I am sure it is probably battery related but wanted to get some response back from the group.

My setup is with 2 Starter batteries in P.
Auto Craft Gold 850 1000 cranking amps. Used but hold a good voltage and I thought together they would do a good job.
Welding info shows:
E = 60J
I = 1036A
R = 1.37
T = 20.5
M = 0000017

I think this is the correct info I got while holding the foot pedal down after a weld.

Anything wrong or odd?

charlie
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flippy   10 MW

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

Post by flippy » Mar 05 2021 7:15am

onyl 1000A?

put the batteries on a lab power supply and keep the batteries floating at 14.4V and when it finishes charging recallibrate the kweld.

that should spruce things up a bit.

ideally you would get be in the ~1500A range.
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Re: kWeld - "Next level" DIY battery spot welder

Post by ossivirt » Mar 05 2021 7:29am

I first saw only one battery connected but at second look you have both paralel. 1000A seems little low for thouse batteries so that could be the issue. I have used 110Ah starter battery and it welds around 1500A so yea..

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

Post by nuxland » Mar 05 2021 9:53am

You can use 1000A when you only weld 0,1mm nickel that has this splitting.
I figured out that I need 200J with my DIY ultracap module (calibrated to 1800A with 11,8V) to weld 0,3mm nickel good.
And I think reason was that I needed to weld it to A123 ANR 26650 positive side and I needed to split it also.

Here is video how I welded 0,2mm nickel for paralleling my cells to already splitted and welded 0,3mm nickel also using 200J.
kWeld is cnnected to Ultracaps (Outside of the video) and laboratory power supply is feeding voltage and current to Ultracaps.
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Re: kWeld - "Next level" DIY battery spot welder

Post by john61ct » Mar 05 2021 11:15am

AGM would put out faster current than FLA.

LI even more so of course.

Also going bigger Ah capacity works too.

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

Post by Hummina Shadeeba » Mar 05 2021 12:18pm

I’ve got way too many a123 cells at batteryhookup that are in great shape I’ll sell for 1.25 a cell. I use 5s15p and weld at 1800 amps

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