kWeld - "Next level" DIY battery spot welder

[tatus1969]

What about putting copper braid between the terminals, wouldn't that allow better electrical contact under less force ? But it would maybe oxidize over time ?

(first post here, I've been lurking for a while, so... hello! )

Hi could be worth a try. Anyhow, at the moment I'm also only giving educated guesses with this regards 8)

 

[panozguy]

I love this idea but I can't quite seem to find the answer I'm looking for. The unit gets the highest praise in the 18650 community, which is what led me here.

Apologies if this has been asked elsewhere - I've done a lot of searching. Even in this thread

I have a dedicated 12V AGM, 100AH battery, practically brand new (4 cycles). Is this adequate to power the K weld 'as is'?

I also have 2 x dedicated 12V LiFePO4 Valence U27-12XP, 138AH apiece. Would those work adequately in parallel to power the K weld 'as is'?

I also have 2 x 12V HP server power supplies HSTNS-PD19, capable of 12V/75A each. I can dedicate one or both of these to the K weld. Will some combination of these power it adequately? Must I also acquire a K Supply? I can modify the power supplies myself easily.

Will there be caveats to using any of these? Increased time between welds, etc?

Thanks in advance! Just needing to make sure I have adequate power supply to run the device before ordering.

 

[tatus1969]

I have a dedicated 12V AGM, 100AH battery, practically brand new (4 cycles). Is this adequate to power the K weld 'as is'?

I don't have sufficient references with regards to AGM batteries. If that battery has a CCA rating, then it should be at least 700A. Deep cycle batteries are optimized towards cycle life and not internal resistance, therefore starter batteries work better. A regular 12V car starter battery of 65AH to 100AH works well, but it should be new and at room temperature.

I also have 2 x dedicated 12V LiFePO4 Valence U27-12XP, 138AH apiece. Would those work adequately in parallel to power the K weld 'as is'?

Do you have internal resistance ratings for the cells, so that the current can be estimated? It might well be that they are too strong.

I also have 2 x 12V HP server power supplies HSTNS-PD19, capable of 12V/75A each. I can dedicate one or both of these to the K weld. Will some combination of these power it adequately? Must I also acquire a K Supply? I can modify the power supplies myself easily.

They can't charge the capacitors by themselves, as the initial short circuit of the empty caps will cause an overcurrent hickup. That's where kSupply comes in place, it regulates current until the capacitors are topped up.

This solution is recommended only for intense use, e.g. when welding larger packs and high firing rate is important. Otherwise, kCap can be charged with almost any kind of current limited source with 8 to 12V output.

Will there be caveats to using any of these? Increased time between welds, etc?

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.

 

[john61ct]

Seems a pain that the spec needs to be goldilicks just right, but varies from job to job.

Which lab-style PSU say (Sorensen) specs would cover the gamut?

Or if I had a "too powerful" LFP bank, wouldn't there be a cheap way to limit the current?

 

[panozguy]

I have a dedicated 12V AGM, 100AH battery, practically brand new (4 cycles). Is this adequate to power the K weld 'as is'?

I don't have sufficient references with regards to AGM batteries. If that battery has a CCA rating, then it should be at least 700A. Deep cycle batteries are optimized towards cycle life and not internal resistance, therefore starter batteries work better. A regular 12V car starter battery of 65AH to 100AH works well, but it should be new and at room temperature.

I also have 2 x dedicated 12V LiFePO4 Valence U27-12XP, 138AH apiece. Would those work adequately in parallel to power the K weld 'as is'?

Do you have internal resistance ratings for the cells, so that the current can be estimated? It might well be that they are too strong.

I also have 2 x 12V HP server power supplies HSTNS-PD19, capable of 12V/75A each. I can dedicate one or both of these to the K weld. Will some combination of these power it adequately? Must I also acquire a K Supply? I can modify the power supplies myself easily.

They can't charge the capacitors by themselves, as the initial short circuit of the empty caps will cause an overcurrent hickup. That's where kSupply comes in place, it regulates current until the capacitors are topped up.

This solution is recommended only for intense use, e.g. when welding larger packs and high firing rate is important. Otherwise, kCap can be charged with almost any kind of current limited source with 8 to 12V output.

Will there be caveats to using any of these? Increased time between welds, etc?

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.

Thank you! The AGM battery is of deep cycle type, not starter. That's OK, I can get a starter battery if needed. The LiFePO4 I have a complete engineering sheet on, but it doesn't have internal resistance figures. Also OK.

In light of all this, I think that your initial recommendation of a high C rate LiPo is probably the fastest and easiest method for me. I was just looking to avoid extra cost when I had existing batteries and power supplies lying around

Thank you!

 

[ChrisFullPower]

Excuse my ignorance but would you be able to weld thin strips of 304 stainless steel to aluminum with this welder? I know nickel strips fail to adhere to aluminum but perhaps something with a little more resistance might have some luck? Thanks.

 

[spinningmagnets]

I doubt it, Al melts at 660C (1220F). Stainless is roughly 1440C / 2624.

Once you get up to the temps to make Al plastic, the stainless is still only warm. If you get the stainless to melt, the Al will likely blow out much sooner.

Most of the 18650 cells have a shell that is nickel-plated steel, so the nickel bus-strips are welding nickel-to-nickel. Of course, there might be a method or technique that might work with the right tools. I just don't know.

 

[ChrisFullPower]

That makes sense. Thank you.

The cells I have have aluminum lids and I'm running out of ideas how to attach anything to them.

 

[Seakane]

If I am posting in the wrong forum, kindly point me in the right direction.

I recently received and assembled a kweld unit. I have a used 750 CCA lead acid starter battery that I connected to the kweld via automotive grade, 4ga wire and typical lead battery clamps. My 4ga to kweld input wire connectors are EC5s.

My calibration test process indicated "Timeout"

I tested the CCA of the battery at 715 CCA. It has not been recently charged.

My 4ga cables are 10" each. That puts my total length at 1.1m. I will likely shorten my cables to get within spec.

With my consumer-grade meter, I get 0 or 0.1 ohms between the battery post and my EC5 connectors.

The kweld reported 1233A after the short and a duration > 200 msec.

Does this point to my battery being insufficient, or perhaps my EC5 connections are poor for high amperage?

Should I check for voltage drop across the EC5s while load testing the battery?

Thank you for your time and patience. I know these are baby questions / concepts for you guys. I appreciate the help.

Aaron
Spokane, WA USA

 

[tatus1969]

My calibration test process indicated "Timeout"

That is the expected result from the SHORT calibration step.

The kweld reported 1233A after the short and a duration > 200 msec.

The current is perfect, but are you sure that it reported 200msec timeout during the calibration SHORT step? The programmed timeout here is 10msec.

 

[Seakane]

I went ahead and did the calibration again so that I could get proper numbers for you.

Post calibration info:

Timeout
n=000004
E=-23.4J
t200.00m
I= 1340A
R=-0.02m
T= 29.4C

I have never tried more than a half a dozen calibrations in a go, but those flexible 8ga wires and pens sure do warm up. I cannot imagine doing too many welds without gloves!

My current came up a little from the other night. Battery must have been cold before I brought it into the house.

Thanks for looking at this for me,
Aaron

 

[tatus1969]

Timeout
n=000004
E=-23.4J
t200.00m
I= 1340A
R=-0.02m
T= 29.4C

That is a result from a regular welding pulse with shorted probes, which is why the cables get hot quickly. This also represents a huge demand from the battery and could damage it.

Please revisit the kWeld operation manual to ensure that you run the calibration procedure correctly.

 

[jonyjoe303]

"but those flexible 8ga wires and pens sure do warm up"

What kind of wire are you using, is it copper clad or pure copper? I recommend you get 6 gauge pure copper welding cables, its what I use. When I was using 8 gauge copper clad the probe cable were getting too hot to hold after a few welds.

When I went with 6 gauge pure copper wire, I was able to reduce the welder power setting and was getting good welds without heating up the cables. Pure copper makes a big difference, I use copper nails as probe tips.

 

[garolittle]

So it has been a while since I posted on this discussion forum. I am the proud new owner of a Kweld unit and I want to make sure I have the proper power source. I will be spot welding .20mm or .30mm pure nickel strips to 18650 batteries. Is the following a good power source for this purpose? Thanks.

https://hobbyking.com/en_us/turnigy-graphene-6000mah-3s-75c-lipo-pack-w-xt90.html

 

[Seakane]

I have read and reread the operation manual --particularly the calibration section as it is pretty much step one.

The manual says I should see an "Offs" value between 50 and 100, typically. When I run the calibration I get no Offs value. After I press the knob, the "Open" prompt goes to "Short" without any information being displayed.

According to the manual, post short test should yield a resistance value of 2.5 - 3.0 milli-Ohms. I am getting an R value of -0.02m. (My value must be an error =/ will this prevent me from making good welds that are safe for the welder?)

Perhaps all is well and I should shut up and go make a battery pack now, but /because/ I have read the operations manual, I am concerned that I am operating out of spec. I do not want to toast my fancy kweld machine.

FYI, my machine is rev3 with 2.9 software.

Thank you for your time.
Aaron

 

[Seakane]

What kind of wire are you using, is it copper clad or pure copper?

I am using the kweld wires and probes found on the kweld website:

https://www.keenlab.de/index.php/product/kweld-cable-electrode-holders/

It was represented to me by the boss that by I am generating much more heat in the calibration process than I will when performing actual welds. Makes sense. No added resistance with probes shorted directly. I have not tried any welding yet due to my concerns about my display values not aligning with values in the manual.

 

[tatus1969]

The manual says I should see an "Offs" value between 50 and 100, typically. When I run the calibration I get no Offs value. After I press the knob, the "Open" prompt goes to "Short" without any information being displayed.

According to the manual, post short test should yield a resistance value of 2.5 - 3.0 milli-Ohms. I am getting an R value of -0.02m. (My value must be an error =/ will this prevent me from making good welds that are safe for the welder?)

It could be that the pedal is wired up incorrectly. Please check with a multimeter if you measure open normally, and short when pressed. You can also try to run the calibration with the pedal disconnected, by using the dial knob to step through the process:
1) push button to enter menu
2) turn knob until "CAL" is displayed
3) push button -> "OPEN" should be displayed
4) push and hold button -> OPEN test executes and results are shown on the screen
5) release button -> screen stops displaying results and shows "SHORT" instead
6) push and hold button -> SHORT test executes including 10 millisecond test pulse and results are shown on the screen
7) release button -> screen stops displaying results and should return to the startup screen displaying "E= ..."

 

[Seakane]

You can also try to run the calibration with the pedal disconnected, by using the dial knob to step through the process:

This is the only way I have operated the kweld unit. I have not connected the foot pedal.

4) push and hold button -> OPEN test executes and results are shown on the screen
5) release button -> screen stops displaying results and shows "SHORT" instead

5#!t. I never /held/ the button down. I will try it tonight when I am home.

6) push and hold button -> SHORT test executes including 10 millisecond test pulse and results are shown on the screen

I typically get the "Timeout" message with a 200.0 msec pulse

7) release button -> screen stops displaying results and should return to the startup screen displaying "E= ..."

will run the Cal test again when I get home. Thank you for your time

Aaron

 

[garolittle]

So it has been a while since I posted on this discussion forum. I am the proud new owner of a Kweld unit and I want to make sure I have the proper power source. I will be spot welding .20mm or .30mm pure nickel strips to 18650 batteries. Is the following a good power source for this purpose? Thanks.

https://hobbyking.com/en_us/turnigy-graphene-6000mah-3s-75c-lipo-pack-w-xt90.html

Sorry. Here is the picture of the battery I am considering. Will this work well for my needs? Thanks.

 

[BVH]

I use two of the exact above Panthers in parallel when welding but calibrate using only one as two causes an over-current issue when calibrating.

 

[garolittle]

I use two of the exact above Panthers in parallel when welding but calibrate using only one as two causes an over-current issue when calibrating.

Thanks. Have you ever tried just using one Lipo like this? Do you parallel them just to get extra capacity? Thanks. Gary

 

[BVH]

Yes, I've used one and it works fine. I'm just trying to be "nice" to the batteries by sharing the load.

 

[Seakane]

Okay held the knob for the "open" part of the test and got the following values:

Offs: 62
Std: 5.6
And: Ok

Still don't know why my resistance value was off from spec at -0.02 milli Ohmes, but judging by the lack of concern here, I think I will forge ahead.

Sorry for wasting your time with my open calibration gaf earlier.

Best regards,
Aaron

 

[tatus1969]

Okay held the knob for the "open" part of the test and got the following values:

Offs: 62
Std: 5.6
And: Ok

No problem And what was the result of the SHORT part?

Still don't know why my resistance value was off from spec at -0.02 milli Ohmes, but judging by the lack of concern here, I think I will forge ahead.

As I said, that was the result from a welding pulse, and *not* from a calibration step. Of course it measures zero then, as you were holding the probes together without anything inbetween. And of course it cannot push energy into 'nothing' which is why it terminated the pulse after 200milliseconds of attempting.

 

[Seakane]

No problem And what was the result of the SHORT part?

Timeout
n=000001
E=-23.2J
t200.00m
I= 1344A
R=-0.02m
T= 29.4C

On a lark I made a couple welds on a dead cell and am getting pretty excited about using this thing in earnest. First pack will be for my 6 year old daughter's Oset trials bike. The stock lead acid batteries weigh more than she does!