6pence Resistance Spot Welder

[pguk]

+1 for kapton tape.
I work for a large defence company and we use it all the time. When building a wiring loom I will cover the wires at a junction with kapton tape. They are thus protected from heat damage when joining braided shielding over the junction using solder. It is tough stuff.

[Valld]

I wish this topic about the extra insulation came up 2 weeks earlier... I did read a ton of information before building my battery and this never came to my attention. I just hope my battery holds with no problems for a long time. But I really doubt with all the nickel, hot glue, foam, heat shrink (x2) and 2mm thick aluminum shell there can be any friction between the cells. The battery fit very tight in the aluminum box, so tight that I had to use some pressure to fit it in the bike triangle and then after installing the lid it felt very, very tight. I believe if you use a soft battery bag the chances for friction and stress between the cells is much higher, that's why I decided to go with the hard shell. Bike completed, tested and I can say I'm pretty satisfied. It's amazing how a 30 kg fat bike feels so much easier to ride than the 10kg carbon everything MTB that I build a few years ago. Picture of the complete bike below:

[Storapa]

The bike looks great Valld. You must be pleased with it.

I wish the subject of Kapton tape etc had come earlier. Several packs that I have taken apart have just been hot glued though. I've noticed that when I was gluing cells together, they don't touch as the hot glue is solid before the cells come completely together. That being said, I will still use a Kapton tape layer in future builds.

[pguk]

A builder in New York state (Lindley) has got in touch:

Hello Paul,

The reflow went fine, I used flat 24 ga sheet copper, 6mm wide, instead of round wire. I fired it up today and it works great with the default settings! The hardest part was building the cables. I'm using a single 85AHr RV battery.

Thanks for making the kit available, it saved me a lot of time.

Regards,
tosa8

If I understand correctly, he has used a toaster oven as a makeshift solder reflow oven. Instead of my method of building up current carrying busbars with copper wire, he has cut flat sheet copper, 24 ga for the busbars and let the oven do the heavy soldering. Genius Thank you Scott !

Here's a web page showing how to do it:
http://reprap.org/wiki/Toaster_Oven_Reflow_Technique

[sacko]

Just ordered

Will have a look at re-flowing.

Looking forward to getting the kit running.

[jerome_speedy]

After some overdue procrastination, I finally finished my build. At first, the welder wouldn't send the pulses. It was because I used a Barrel jack>RCA adapter for connecting the foot switch, but the adapter didn't work Initially, I bought that adapter to save me some work, but in the end, had to cut the foot pedal cable to solder a RCA connector anyway. That taught me a lesson for cutting corners ... Hooked the device to my Marathon 85 Ah solar batteries (yeah, I know they're not meant for that) and a homemade 12V LiPo Pack. First tests on a piece of nickel strip: it didn't survive the surge whatever the settings. After pushing the nickel strip firmly onto the cells, and reducing the settings to the minimum (something like P1=0.1 P2=0.2 D=5), the welds happen, and the result is pretty ! Very very satisfied, I now have all the tools to get my project going !!
The power-on LED doesn't light up, probably because it's a blue one, and needs a higher voltage. Will fix that if I find the time.

All in all, thank you pguk, for selling this spot welder (and power board) on ebay cause it prevented me from buying the chinese MOT welders that have very bad reputation I would never have thought there would be such a project on endless-sphere ! So useful ! And takes little space

[Offroader]

Would you consider this the best DIY spot welder on the market right now?

[Animalector]

don't know if it is the best, as i haven't tried the others, but it's a good kit, easy to build, and works well. Also does not cost a fortune. I'mm happy with mine. .

[smurphy]

After i melted my Sunkko welder i got this DIY welder from Paul.

Easy to assemble and works like a dream. No loud noises like the 709A and always perfect welds.

Highly recommended.

IMG_20170711_162243 (Small).jpg (108.93 KiB) Viewed 3288 times

[mxer]

Looking closely at the fets out of the 6 pins only 5 are soldered is this for a reason or can you just run solder over all 6 pins?

[Animalector]

One is the gate. The signal to activate the FETs. This must be isolated from the rest.

[mxer]

One is the gate. The signal to activate the FETs. This must be isolated from the rest.

Thanks

[pguk]

All 6 pins are soldered, but the leftmost pin is the gate. It goes to the underside of the board where all of the SMT gate resistors are located.

So chuffed to see folks results, thanks again all for posting.
Just to say, after sales of 40 plus of these kits I haven't had any folks get in touch to say 'It's broken - help!'. Apart from one guy in Belgium last week who put +12v on the foot switch by mistake. He said the unit still booted up, but would no longer trigger a weld because the I/O on this pin on the chip had blown. I could have re programmed it to use a different pin, but he was in a hurry so he requested a fresh chip.
Lesson: probably best to use different connectors for the foot switch and +12v input if you want to be sure not to have the same thing happen.

[yosemite]

I need some advice/ help
I need to connect copper automotive cable to brass terminals to rebuild a vintage motorcycle wiring harness.
in the past I've used various means, solder, aluminum crimp type crimp brass , and have had problems with all of them either through corrosion or vibration, as the bike will be ridden in all weathers, seasons, and states of salt and mud on the road as well as prolonged periods of wetness (Scottish border weather is to say the best not good)
the only type of connection that seems to survive for a reasonable time is the original Japanese type where the connector(brass )is welded to the cable (copper)
so my question is has anyone tried this with this type of welder? I would guess that the electrodes would need to be changed from copper and that the current would need to be high to get the material to fuse but these are just guesses so if anyone has any experience of this type of welding any information/suggestions/advice would be extremely useful
Thanks
Yosemite

[fechter]

I don't think a pulse welder like this would have enough energy to weld a big copper wire. One made from an old microwave oven transformer might. If you search around you can find several topics about rewinding old microwave transformers.

[coolbobjoe]

what do people think of using a capacitor bank combined with a lithium ion cell bank together to power this unit? trying to get it all worked out before it arrives in the mail soon. I could make a 5 x 2.7V 400F bank for about $70 brand new unless i can scavenge some parts. I have plenty of old li ion cells to power it mainly but I want to make sure there are no large low voltage fluctuations due to their age and random stages of abuse.

[spinningmagnets]

I need to connect copper automotive cable to brass terminals

I believe a resistance soldering unit (RSU) would work in this application. This is where current is passed through the work-piece to heat it. One of the jobs that an RSU is used for is thick copper plumbing joints where a torch cannot be used. Of course the thicker the piece, the higher the amps that are needed. A high-current RSU can be made for under $100.

"Resistance Soldering Bus Strips to 18650 Cells"
https://endless-sphere.com/forums/viewt ... 14&t=88965

"DIY MOT-based [home] Resistance Soldering Unit (RSU)"
https://endless-sphere.com/forums/viewt ... =2&t=89289

[Pedrodemio]

Just finished mine

I have two problems, but both are easily mended

First, apparently my battery isn't up to the job, it's a 3S 5000mah 35-70C Turnigy nanotech, i preferred to teste with it since car batteries are not cheap around here. First i need to charge it since it was sitting for more than 2 years at storage voltage, i was too impatient to test, if that doesn't work i have another one i can put in parallel

The problems are that the 0.15mm nickel sticks very bad to the cell, 1ms first pulse and 20ms second was as far as i got, and it made a little holes in the nickel

Second are my welding tips, i'm using TIG electrodes ofr steel, i thought they would be better than cooper due to the higher melting point, but they stick pretty well to the tab

[Alan B]

The steel probes are higher resistance than copper, so they will limit the current.

[Pedrodemio]

Everything works perfectly now. Switched to copper and two batteries in parallel, using 1.5 and 6ms I can weld 0.15mm nickel with no problem

[coolbobjoe]

And down goes the spot welder....

Finally got everything assembled and sourced and started getting work done on the 22s7p battery I have been waiting forever to build. First night was a total success. Got almost half of the battery done and a couple thousand welds put into the unit. Put everything away for the night and week and come back to nothing. about every ten peddel presses i get a small little arc and thats if its feeling happy. Not sure what the hell could have gone wrong while sitting there for less than a week with no power to it..... Any ideas? Havent gotten any responses from OP yet

[pguk]

A little testing will help us find out what has failed.

If you can disconnect the gate wire between the two boards we can test if we have output from the control board. If you don't have a 'scope, next best thing is to try to light an led. Put and led in series with a resistor (200 ohms or so) and put this across the control board gate output to ground. Increase pulse time to something you can see, and fire a pulse. If led flashes, the gate drive chip is likely good and your problem is on the power board. If no flash, driver chip can be easily replaced as I made it socketed.

It's a bit rum that you have raised a PayPal claim against me I have no control over how folks build the power board. Eg If you put too much heat for too long on the fets, they may have been weakened. How can I be liable when I have not built the power board? This is why I offer no guarantee.

[Buk___]

6pence Resistance Spot Welder (brain board)

Will a device like this reliably and safely attach the 0.5mm lead of a component (polyfuse) to the top of an 18650 cell?

Thanks, Buk.

[SMC -highly recommended]

Hi there am new here and I would like to know how much would it cost to ship one of this spot welder kits to the USA?

[Animalector]

I recommend this kit. Postage to Australia was very reasonable. Like $15 or $20.. anyways it's not like it's hundreds....

Good luck

Andy