mega copper battery spotwelder

so i thought id start my own thread on this here, as i dont want to hijack other, "normal" battery spot welder threads and spam them with crayzness to confuse folks about whats acceptable in a battery spotwelder :lol:

i have a riba welder that i bought some time back and never used. im sure its fantastic for nickel welding but i need more current capacity from my packs than nickel can comfortably supply.

my plan is to use its timing circut and build my own power switch system.

i now have all the parts required except the fets, i have 20*irf 1324 s7pbf which i ordered, then decided to return them and get better ones, the ones used in the kwelder, FDB0105N407L.
namely because of the vast difference in the critical specs-
(1324 vs FDB0):
single pulse avalanch energy 230 mj vs 1109 mj
max pulse drain current 1640A vs 2540 A

the cost of the 2 types of fets was actually very comparable-$110 vs $125 aud for 20.

the aim is to be able to comfortably weld 0.15mm copper to cells, copper to copper, COPPER TO EVERYTHING!

so next i plan to tap threads in the copper bus bars, (i know its gonna be tough) and clamp the (20)fets to the copper bar.
i could also use the ~2mm copper sheet i have and make it broarder, do it in a wye config, but id rather save it as a surface for building my packs on :wink:

i plan to use the cable i have in the pic as the electrode cables but i want to individually insulate the strands, to parallel the inductance. so i might have 10 or so of the thick strands in each cable, and keep them short, each wrapped in heat shrink or some sleeving.

for the power source, i will first try the 3 large 150ah sla batteries i have in parallel. i dont know what their ir is like, but they weigh 60kg each, and have got to pack some kind of punch.
my diesel pickup jump starts very enthusiastically with one

the electrode tips will be 9mm copper rod with 1.5mm*10mm tungsten tig electrode press fitted in the ends. i have found this to work well in the past with coil spot welders.
i will also try doing the welding in an argon gas bath, to reduce brittling of the tungsten tips from oxidation.

though i have used AC coil based spotwelders for copper, this is my first attempt at building a fet switched welder so id be keen to hear any advice from any experienced ES folks.

ill be posting more pics with updates as i build.
Cheers

Wow ! I want to see this !!!
You will need extremly high power compared to nickel.... Basically you need a pulsed TIG welder like the Orion Sun Ev welder !

I don't have experience personally. Your like Niel Amstromg, the first man to walk on the moon! Haven't seen anyone get as serious as you with the heavy duty equipment before. Wish you success!

I will follow this tread. Subscribed!

Matador

Just when you wonder if the Sphere is starting to go soft, somebody picks up the reins and goes wholly and appropriately overboard.

Good luck !

silentflight said:

Just when you wonder if the Sphere is starting to go soft, somebody picks up the reins and goes wholly and appropriately overboard.

Good luck !

Click to expand...

Yeah, stay tuned next month for a thread asking where to procure plutonium for a home made reactor powered spot welder.

Taswegian said:

silentflight said:

Just when you wonder if the Sphere is starting to go soft, somebody picks up the reins and goes wholly and appropriately overboard.

Good luck !

Click to expand...

Yeah, stay tuned next month for a thread asking where to procure plutonium for a home made reactor powered spot welder.

Click to expand...

100 megawatt spotwelder... Plutonium powered... That should be very heavy to lift with all the lead shielding.... The trouble is how to manage such high power without melting through the cell !

I want to see this as well. I have a 10,000 amp capacitor discharge welder (800 watt second) and it didn’t really phase the copper to cell connection.......like it wasn’t doing anything. Tried glidcop, copper and tungsten electrodes and nothing worked for me. Love to find the secret to copper welding success.

Tom

Taswegian said:

silentflight said:

Just when you wonder if the Sphere is starting to go soft, somebody picks up the reins and goes wholly and appropriately overboard.

Good luck !

Click to expand...

Yeah, stay tuned next month for a thread asking where to procure plutonium for a home made reactor powered spot welder.

Click to expand...

yeah, i couldnt get any plutonium, my Russian connection said some guy from Syria just bought out their stock
looks like ill have to settle for batteries for the mo.

thanks for all the comments folks!
im passionate about this. i have used a modified dn10 ac coil spotwelder(mod was just to make a diy timing board to get better pulse control)
it does a great job on 0.1mm copper except for one thing- we could never completely eliminate the tendency to get a double pulse intermittently, as the ssr we used for switching the 240vac supply to the coil primary would sometimes switch where the ac waveform crosses the "0"point.

I tried using an old transformer arc welder too but that was not constructed correctly for the purpose, it had too much airgap in the center of the coil and poor coupling between the primary/secondary coils, so although it was huge, it was only good for 0.15 nickel :|

i finally blew that up when i tried to get the primaries to work in paralel instead of using just the one, it kept blowing the nickel wire in the fuse box so i wound extra copper in the fuse box tried again and there was a loud !BANG!
it actually wasnt the coil i think, it was the expensive high current ssr, that had blown completely open
i conclude that i had wired the coilds the wrong way.
yeah had enough of ac coils and ssr's, lets move on to mosfets

litespeed said:

I want to see this as well. I have a 10,000 amp capacitor discharge welder (800 watt second) and it didn’t really phase the copper to cell connection.......like it wasn’t doing anything. Tried glidcop, copper and tungsten electrodes and nothing worked for me. Love to find the secret to copper welding success.

Tom

Click to expand...

i almost cant beleive this. it sounds like it should have been able to weld atleast 0.1mm copper.
did you try splitting the copper or welding 2 peices to the cell with electrodes on either side?

I tried multiple ways with copper and yes I split it and tried separate pieces.

Tried brass also.....I think pulse arc is the way.

Tom

i wonder if i could use my tig welder with diy pulse timer..

I'd like to be proved wrong but I think when you get enough current to make that copper heat up enough to weld you will blow holes in the battery electrodes.

my feeling is above 0.15mm, you might be right.
the dynamics of copper welding are very different from nickel welding.
because copper conducts so well it pulls any excess heat away very fast.(also one reason its tricky to weld)
the danger is if you have not got the surfaces super clean or you hit the plastic wrap on the side
yeah, pretty big holes can happen.

why not just learn to tig weld?

so this is sort of but not really quite an update.
i have now received a prebuilt power switch and pulse control board from a webshop in china, who was making these spotwelders.

it looks very well built except for one easilly rectified detail- the bus bars that carry the current to the electrode are the wrong thickness, causing a terrible contact. the copper strip is ~1.9mm. where it should be the same thickness as the pcb, around 1.55mm thickness, to keep the surfaces aligned properly. the fix- remove the copper bus bars, and bolt on some heavy duty copper bars to both sides of each terminal, with a 1.55 coper or aluminium strip in between to keep the correct spacing.


i have already removed the stock bus bars, now just hunting round in my stash for the right thickness.

i now see the builder has put tiny ferrite rings on the gate legs, i think to even out the respective turn on times of the fets.there is also a tiny smd gate resistor on each gate, something i did not notice in his pics when I ordered it.

I still intend to build my own power switch with good quality heavy duty fets, but cuase i have so much stuff going on at the moment, i thought id try this one out in the interum.
ps. was bought from here-
https://www.yousun.org/product/spot-welding-72xmosfet-switch

Theres another thread around here where the builder put a 0.20mm copper strip on the cell-tip, and then covered it with a 0.15mm nickel strip. It welded very easily.

Theres something about the nickel sandwich that focuses the weld-pulse, instead of spreading it out...try it.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=84680&start=175#p1470809

the resistor and ferrite core is to get rif of the parasitic oscillation between the parallel mosfets so you get more stable on/off switching.
with that many mosfets you will otherwise get mosfets turning eachother off and on and blow the arse out of the entire board.

still, if they used proper mosfets they could do the same with just 1 row.

Wow, that's going to take one big gate driver.

Any updates on this? I'd love to know if this can actually weld copper reliably or not.

com'n slowly but surely
just getting all the little things to happen to arrive at welding...feels like im climbing a mountain made of honey

ridethelightning said:

com'n slowly but surely
just getting all the little things to happen to arrive at welding...feels like im climbing a mountain made of honey

Click to expand...

I know, it can be really annoying when people mess up the order or take forever to send things. I might mod my Sunkko whilst I am waiting for the results of your project.

so finally some noteworthy developments that qualify for an update.
So I have slowly been chipping away at this project over the last 14 months....
and finally, after running it on a big 150AH lead acid to weld Nickel strips to make the 18650 welder pack, i finally finished said pack and have it fully operational.

I had some odd bod cells kicking about, some spares left over from packs i built, some were from slightly toasted samsung necro packs i managed to revive, some were from dyson vacuum cleaners, cordless drills, etc etc. most are samsung 25r that got discharged flat by a customer of mine and were then left in the garage for several years..
needless to say, this whole thing is quite far from the "safe" or "good idea" range of the hobby project spectrum, and is outdoors only
The pack is 3s 80p, sitting at 12.12v.I have not capacity tested any of the cells, as i thought its not really important for this job, just the instant discharge current.
these 25r cells are still good for some punch. some were actually ok after the pack went flat, sat at ~4 volts for a year or so. others were at 2volts, some at 0.7volts, i managed to charge them ok and they hold charge, there were some at 0v, they wouldnt charge. thats what im using for weld practice.

ill be trying to push the limits to see what it can actually weld in the next few days, ill post pics when done

This'll be interesting 8)
sub'ed

Seems your big battery has alot of reserve being as large as it is. It also adds alot of resistance. You would be better off with a single 3s lipo with a 75-100c discharge for more punch. This single battery would have very low internal resistance and would cost around 75 to 100 dollars thou.

Bigdaddyhawk said:

Seems your big battery has alot of reserve being as large as it is. It also adds alot of resistance. You would be better off with a single 3s lipo with a 75-100c discharge for more punch. This single battery would have very low internal resistance and would cost around 75 to 100 dollars thou.

Click to expand...

thanks for input. i used the semi necro 18650s i had lying around as i wanted to put them to some use. the results have been very satisfying and way more than adequate for the task i need to use the welder for. i was considering ordering some lipo4 high discharge cells which would have been a little safer, but the lipo you suggest would no doubt be cheaper than that.

i would think a dozen supercaps would be a more effective solution then using batteries. also simpler, safer and more robust then lipo. and more consistent to get insane amps.