kWeld - "Next level" DIY battery spot welder

[serious_sam]

Thanks again. That actually gave me an idea. Would tungsten electrodes be an option since they have higher resistance? That may put me under the 2,000A limit but still provide enough current to weld copper strips. What do you think?

Sounds promising. They'll get hot much quicker than copper electrodes, so your holder will have to have good insulation.

[garolittle]

I'd say your theory is spot on, the copper strips have significantly less resistance and push the current above the limit. I'd also try using partially discharge batteries first.

Thanks Sir and thanks again for making such an awesome product!

[garolittle]

Sounds promising. They'll get hot much quicker than copper electrodes, so your holder will have to have good insulation.

I will try and report back. Thanks for the response.

[No_Shorty]

I doubt it, Al melts at 1221C (2230F). 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.

Not that I know anything about it, but I had been Googling Aluminium melting temp earlier today for another reason and the answers I got were 5-600deg for most Al alloys.

[garolittle]

Would the resistance reading after a spot weld be a good proxy for the resistance of the material being welded (assuming the strips are identical in size and are being spot welded to the exact same battery)?

I had success in spot welding two different materials (SigmaCLAD and “Nickle Silver”) using the Kweld. The materials are similar in thickness so I obviously want to use the one with the least resistance. I tried to measure the resistance of both materials using a multimeter but could not get a good reading. It may be an over simplification but it seems like the resistance reading after each weld would answer this question. Thanks for any suggestions or responses.

[ossivirt]

Would the resistance reading after a spot weld be a good proxy for the resistance of the material being welded (assuming the strips are identical in size and are being spot welded to the exact same battery)?

I had success in spot welding two different materials (SigmaCLAD and “Nickle Silver”) using the Kweld. The materials are similar in thickness so I obviously want to use the one with the least resistance. I tried to measure the resistance of both materials using a multimeter but could not get a good reading. It may be an over simplification but it seems like the resistance reading after each weld would answer this question. Thanks for any suggestions or responses.

You can also try spotweld pulse with long strip. Like 10-30cm or so with electrodes on oposite ends without a cell. That could give most accurate results regarding resistance difference of different materials. I did this with 0.1 and 0.2 copper but I did not compare the readings, just felt how hot it would get . However that "new" antispark function that was added after that test may kick in and not give good results

[garolittle]

You can also try spotweld pulse with long strip. Like 10-30cm or so with electrodes on oposite ends without a cell. That could give most accurate results regarding resistance difference of different materials.

Very clever idea. I will try it. Thanks for the suggestion

[garolittle]

You can also try spotweld pulse with long strip. Like 10-30cm or so with electrodes on oposite ends without a cell. That could give most accurate results regarding resistance difference of different materials.

Very clever idea. I will try it. Thanks for the suggestion

Yep. It worked. It makes sense because the only variable is the material being spot welded. Here are the results:

Setting for each spot weld: 50J
Length of each strip: 3”
Width of each strip 9.1mm
Results:
“Nickel Silver” .25mm thick: 1.70mR
Nickel plated copper .25mm thick: .65mR

Basically the same results after several attempts.

[tatus1969]

You can also try spotweld pulse with long strip. Like 10-30cm or so with electrodes on oposite ends without a cell. That could give most accurate results regarding resistance difference of different materials.

Very clever idea. I will try it. Thanks for the suggestion

Yep. It worked. It makes sense because the only variable is the material being spot welded. Here are the results:

Setting for each spot weld: 50J
Length of each strip: 3”
Width of each strip 9.1mm
Results:
“Nickel Silver” .25mm thick: 1.70mR
Nickel plated copper .25mm thick: .65mR

Basically the same results after several attempts.

Interesting idea Don't expect too accurate results please, as kWeld isn't a precision istrument. I use to measure low resistances with a bench power supply and a multimeter: set the supply to as much current as possible and connect it to the ends (I have decent crocodile clips for that). Then use the multimeter in millivolt range and probe across a known length, anywhere on the nickel strip that is carrying the current. Divide measured voltage by given current, and you have the precise resistance for that length.

[garolittle]

Interesting idea Don't expect too accurate results please, as kWeld isn't a precision istrument. I use to measure low resistances with a bench power supply and a multimeter: set the supply to as much current as possible and connect it to the ends (I have decent crocodile clips for that). Then use the multimeter in millivolt range and probe across a known length, anywhere on the nickel strip that is carrying the current. Divide measured voltage by given current, and you have the precise resistance for that length.

I will try that. I really appreciate the suggestion. I appreciate the Kweld even more. It is simply awesome. Thanks again.

[Alex_uppfinner]

Hello!

I would just like to say that I am very happy with the results of using the kWeld, even just with a LiPO-pack as power source.

All welds (most at 35J for 0.15mm some @ 85J for 0.25 mm) were good. Built my first own battery (5P16S) without any issues.

Se relevant build thread: viewtopic.php?f=6&t=107007

/Alex

IMG_20200613_185436.jpg (408.89 KiB) Viewed 1125 times

[garolittle]

It is an amazing product isn't it? Welcome to the Kweld World.

[SubnetMask]

It is an amazing product isn't it? Welcome to the Kweld World.

Absolutely. I haven't used mine much yet because I've been awaiting the delivery of a MegaCell Charger to allow me to do better charging and testing than my LitoKala charger can do before I build more packs, but what I've done, right out of the gate, it was orders of magnitude better and more consistent than the Suckko spot welder I had tried before. The Suckko welder COULD NOT do .2mm nickel. Look at it hard and it would pop off. Even .15mm nickel plated steel was somewhat iffy. The kWeld? No problem. It is rather amazing that something powered off 120v mains is junk and something powered off (in my case - I charged my 3s packs, which I ran in a 2p config, up to 3.8v per cell in order to provide ample current but try to minimize the abuse to the cells) 11.4v batteries blows it out of the water.

[garolittle]

Yes sir. That’s the difference. Excellent engineering of the Kweld

[dejanc]

I would like to ask users of kWeld, how is the status of heat, working temperature?
I do not see any sink heaters, or fan?

Thanks for answers...

[ossivirt]

I would like to ask users of kWeld, how is the status of heat, working temperature?
I do not see any sink heaters, or fan?

Thanks for answers...

Never had any issues with the unit itself. Electrodes on the other hand get too hot to handle without gloves if pulse energy and time between welds dont allow enough cooling.. Unit has temperaturesensor and will protect itself if needed.

Edit: Next time I have to try with welding gloves

[garolittle]

I would like to ask users of kWeld, how is the status of heat, working temperature?
I do not see any sink heaters, or fan?

Thanks for answers...

Wear a good pair of gloves and point a fan at the pack and the cable holders while welding. Take short breaks to let things cool off. Also, some people use electrode cables a large as 4AWG which reduces heat.

[agniusm]

Ordered this unit for the odd jobs i have. Was wondering how many weld you get out of 5ah lipo?

[flippy]

Ordered this unit for the odd jobs i have. Was wondering how many weld you get out of 5ah lipo?

just keep a dumb charger on it and keep it floating at 4V per cell.

[agniusm]

Received mine:





Thanks

[garolittle]

Received mine:





Thanks

Looks good. Get ready for the best spot welder you have ever used:-)

[ridethelightning]

Looks great!

[agniusm]

Have to confirm that the welder is brilliant. Very minor thing, but would be nice to have welded studs for input output wires(nut on top)
Welds are very good and i like the "charging" pitch audio feedback on Auto.

[Portugaline]

Hello people,

I made an order on the website, anyone knows how many days it usually takes to be sent?

[eee291]

These are unusual times, also it depends on where you live.