Want a battery spot welder that works for £20?

[Lucifer]

Anyone want a cheap spot welder for £20

Right I was asked to start this thread off and happy to do so, as so many people have helped me on this forum. First only fair I let you know I am a complete novice at making batteries, but that said it means that if I can do this then so can you. Now this is going to take me longer to write up than it took to build the battery so I will do it in parts.

IF YOU WANT A FAST CHEAP SPOT WELDER this does have a happy ending LOL

So part one..... An overview of the spot welder.

Basically a while ago I decided to build a battery started getting everything together, purchased a cheap chinese battery spot welder on e-bay for under £20, which at the time was the cheapest one I could find. Then just before I could start I became very ill and the whole project sat in the garage for over a year, by the time I got back to the project, I had lost the instructions, and forgotten how it worked.

This turned out to be a blessing in disguise as I googled it and found very mixed results, some people saying it was great, others saying it was a complete waste of money. During this research I discovered that the device had a built in weakness that caused it to blow, if the power of the battery dropped, which it tends to when spot welding with it.

The good news by the time I got back to the project other people had found the problem and come up with a simple modification that will fix this issue, this involves soldering an extra capacitor in place.

Now this is a link to the actual spot welder I purchased

This is the actual one I purchased, though not necessarily from this seller.

There are now lots of copies of this on e-bay and come cost as little as £10, but I cannot personally comment on them having never used them.

Now if you search Youtube for "Transistor Portable Mini Spot Welder Welding" (video) you will find various You Tube videos, some good some bad.
Amongst them you will find a couple by a guy called Adam Welch, the first one was a review of the product, when he bought one to test it....... And blew it up, so thought it was a waste of money. Well Adam has his own channel, and several people told him of this built in weakness and a simple mod that fixes it.

So Adam put up a second 21 min long video where first he fixes the one he blew up. but then does the main mod of installing this extra capacitor. its clear, good audio and easy to follow. Of course if you skip blowing it up first like I did and go straight for the mod then you don't have to pay attention to him fixing his first.

Adams second video on the repair and more importantly the mod is at the link below.

This is Adams Second video, half is fixing his the second half is the modifications

The capacitor needed or the on I purchased to do the job was a Radial Electrolytic Capacitors / Value 1000uF, Voltage 25v, I bought two of them on e-bay for £2.15 p (you only actually need one, I bought a spare).

Now Adam also reinforces much of the PCB track with extra solder to reduce resistance but one of his followers pointed out that another common improvement is to use two batteries, one for the electronics and one for the weld current, if you do this you don'[t need to do any extra soldering at all (so I didn't) I went for the two battery approach.

Below is the actual post quoted exactly that tells you how to do this.

"@paulh71 also on You tube in the comments under Adams Post

You can also just use a second smaller 12V battery for the control electronics, and connect the +ve welding cable to the +ve of larger battery and the -ve welding cable to the normal -ve welding connection of the board, then connect the -ve board connection to both -ve ‘s of batteries, and the +ve of the smaller battery to the +ve of the board . This prevents the control voltage from dropping during a weld, and doesn’t need any additional soldering."
So I did that as well, while in the process I extended the leads a bit as the ones in the pack are a bit short to work comfortably with especially with two batteries. So I use a 7.5 ah Sla battery for the electronics, and a car battery on the floor for the weld current.

That's it folks. There are also some other videos on tips how to use this to get better results using this device.

One said round the end of the probes a bit (so I did that did that with sandpaper). The others are tips about technique, I'll look for them next time. but basically its a knack, at first you tend to push too hard DONT you want some resistance between the nickle strip and the battery, no resistance = no heat. Also most pro welders both probes come down at 90 degrees to the work piece. This one definitely works better one probe in each hand, both at about the angle you would have a pen or pencil when writing.

I had a practice on some scrap batteries first, once I got the weld current adjusted correct, (About 45 on mine with my setup, but will vary depending on electrode lead length and battery condition). It took me about half a dozen practice goes, then went straight into doing 1500 welds to build a battery, no problems at all, just a few tea breaks.

Well hopefully that will get the ball rolling feel free to comment, criticise or ask questions.

Lucifer (AKA Keith)

 

[Skyler]

IF YOU WANT A FAST CHEAP SPOT WELDER this does have a happy ending LOL

if you want to start a fire fooling around with garbage and burn down your house go ahead.

ME. I would

rather buy a decent AC powered spot welder. Modifications are for experienced folk but if just want to spot weld a battery without a degree in electrical engineering ; Common folk need to spend around $200 on a reliable machine and get real.

See my post here on battery technology.

18650 - 26650 0.1 to 0.3mm spot welders

Skyler

 

[scianiac]

I actually have one of these, well two since one half died in a different way as the display output is dead but otherwise works fine. That one was probably my fault as I reused some diodes that I didn't realized I previously had damaged. But the other mods I would suggest which should make it last longer would be to install large diodes and TVS diodes to protect the mosfets. A common failure mode of mosfets is repeatedly subjecting them to voltage spikes, this eventually will cause them to fail although it will take some time. Diodes between the output leads to short the voltage spike from the cabling inductance. Then TVS diodes across the FET with a lower breakdown voltage than the FETs. Also a good idea is to make sure to keep the cables far apart if possible. Safety wise a fuse would probably be a good idea too like the Kweld has.

 

[Lucifer]

I actually have one of these, well two since one half died in a different way as the display output is dead but otherwise works fine. That one was probably my fault as I reused some diodes that I didn't realized I previously had damaged. But the other mods I would suggest which should make it last longer would be to install large diodes and TVS diodes to protect the mosfets. A common failure mode of mosfets is repeatedly subjecting them to voltage spikes, this eventually will cause them to fail although it will take some time. Diodes between the output leads to short the voltage spike from the cabling inductance. Then TVS diodes across the FET with a lower breakdown voltage than the FETs. Also a good idea is to make sure to keep the cables far apart if possible. Safety wise a fuse would probably be a good idea too like the Kweld has.

Thanks, did you do the install an extra cap mod, and use two batteries?

And what's prob most important to most people reading this, how do you find it welds, I'm OTM with mine.

Keith

 

[docw009]

Purchased late 2021. One of the early designs that worked with the capacitor modification, By the time you buy a 3S RC Lipo that does 300 amps and a good charger, it's $120.

I originally had it running on a small car battery, but was doing close to full power settings for .2mm and I could see the welds burned, Also, at that power level, if I put the weld off center, it could easily blow a hole in the cans. Switched over to RC Lipo, and it runs at half power and is repeatable, Far less risk of danage, Worked well enough, I bought a second one as a spare. Probably have done over 3000 welds.

If you run Lipo, use your smart charger to put the battery to storage voltage when not in use, Those are in the battery instructions. If not done, the battery will degrade and swell up in a few months. It's also safer.

I prefer to use ,15 mm nickel in my batteries, and they're designed so 8mil x .15 is enough for series cell-cell current. Easier to weld. You can double up nickel, when necessary. If I use a pre-made case with holders, I'll buy their stamped metal interconnects, even though they may be plated steel, For that style of battery, with a 25A BMS, the nickel plate is good enough, and welds easy too.



If the Kweld guys had used a reliable US distributor in 2021, I would have bought one, At the time, you had to join a facebook page, do messaging, and poke the guy to get a response, I heard he was pretty sick and out of commission, but I needed a welder. So I went down the cheap path, Most of them don't work and.or blow up, I can attest to that, spent more on the junk that a Kweld would have cost,

 

[Lucifer]

Purchased late 2021. One of the early designs that worked with the capacitor modification, By the time you buy a 3S RC Lipo that does 300 amps and a good charger, it's $120.

I originally had it running on a small car battery, but was doing close to full power settings for .2mm and I could see the welds burned, Also, at that power level, if I put the weld off center, it could easily blow a hole in the cans. Switched over to RC Lipo, and it runs at half power and is repeatable, Far less risk of danage, Worked well enough, I bought a second one as a spare. Probably have done over 3000 welds.

If you run Lipo, use your smart charger to put the battery to storage voltage when not in use, Those are in the battery instructions. If not done, the battery will degrade and swell up in a few months. It's also safer.

I prefer to use ,15 mm nickel in my batteries, and they're designed so 8mil x .15 is enough for series cell-cell current. Easier to weld. You can double up nickel, when necessary. If I use a pre-made case with holders, I'll buy their stamped metal interconnects, even though they may be plated steel, For that style of battery, with a 25A BMS, the nickel plate is good enough, and welds easy too.

View attachment 338539

If the Kweld guys had used a reliable US distributor in 2021, I would have bought one, At the time, you had to join a facebook page, do messaging, and poke the guy to get a response, I heard he was pretty sick and out of commission, but I needed a welder. So I went down the cheap path, Most of them don't work and.or blow up, I can attest to that, spent more on the junk that a Kweld would have cost,

Thanks for the reply.

I watched a couple of videos on how to use it, and i found the tips about angle and not to firm a pressure worked perfectly, I have only done a couple of thousand welds (built a 36v 18650 battery put 6 spots on each connection, and a lot were little bits of nickle so ended up three layers thick in places with them top and bottom is a lot of welds, but it knocked it out pretty quick, when testing or learning how to use it I did manage to burn a couple of holes, but that was either too little pressure, or to high a setting, obviously that will depend on your cables, and batteries and the setup etc, once my test welding showed me 45 was optimum for my setup, it did a couple of thousand with only tea breaks for me LOL.

I saw your post in another thread, and I'm just going to check out the one you suggested there. atm I'm happy with this BUT it was cheap, its built one battery and I'm about to build another, not sure of its longevity, even with the mods, but at £20 compared to all the other components, its not the end of the world, if it dies, certainly if it completes the second battery I would think I had value for money.... Lol

K

 

[Lucifer]

if you want to start a fire fooling around with garbage and burn down your house go ahead.

ME. I would

rather buy a decent AC powered spot welder. Modifications are for experienced folk but if just want to spot weld a battery without a degree in electrical engineering ; Common folk need to spend around $200 on a reliable machine and get real.

See my post here on battery technology.

18650 - 26650 0.1 to 0.3mm spot welders

Skyler

Cama'i tang’rciqamken camiku

 

[999zip999]

I guess it means more than just goodbye. Haha.

 

[Lucifer]

I guess it means more than just goodbye. Haha.

A polite message in native Alaskan, a variety of Inuit.

 

[Lucifer]

I guess it means more than just goodbye. Haha.

But very close, good guess

 

[scianiac]

I did not do the mod (yet) and it's possible that's why I blew a FET and not the reuse of dodgy diodes. There seem to be two different versions of the red ones and they each require different mods: https://www.youtube.com/@Luca_Techy/videos

Also is seems like the purple single board ones are better and cheaper. They have faster mosfet switching.

 

[Lucifer]

I did not do the mod (yet) and it's possible that's why I blew a FET and not the reuse of dodgy diodes. There seem to be two different versions of the red ones and they each require different mods: https://www.youtube.com/@Luca_Techy/videos

Also is seems like the purple single board ones are better and cheaper. They have faster mosfet switching.

Yeah I think the purple boards are newer versions, but you think they would of ironed out the bugs by the time they bought out a new version. Much more technical review, and would need to watch it a few times if I had one of them, before doing the mod. And while technically it looks better with much more detail, it's also a more complicated fix which would certainly put many people off.

On the older board that I have at the end of the day, the mod I had to do was solder one cap in place, and connect it to two batteries (instead of one), one to runs the board and a second bigger one for the weld power, so almost anyone could easily tackle it even if they did not understand a word as to why they were doing it, Ill watch it again later, because as they are so cheap I was thinking of buying a second one in case the first dies at any time in the middle of doing a battery, its build one, If it gets thru the second one ok, then I have had my moneys worth, they are cheap enough to be disposable at that price.

Putting it in perspective I have a couple of rolls of resin core solder that I bought years ago, seem to last for ever, but I have a horrible feeling that when I finally have to buy a new roll, it would cost more than the welder LOL.

I know you can now buy small tubes with a coil of solder in them and would probably do that next time (got one somewhere if I can find it)

Keith

 

[Skyler]

I saw a new video how to mod the unit.

Cheap 18650 Spot Welder Reliability Mods and Test​

I threw my unit in a dumpster so no mod for me.

I do not see any sense in ordering something that needs upgrades when you can simply order a real machine that runs off or AC and can have a pack or two finished building in the time it takes to mod a cheap dysfunctional portable DC powered unit.

I will wait and buy a real machine next month.

Good luck with that.

You will need it.

Skyler.

 

[Lucifer]

I saw a new video how to mod the unit.

Cheap 18650 Spot Welder Reliability Mods and Test​

I threw my unit in a dumpster so no mod for me.

I do not see any sense in ordering something that needs upgrades when you can simply order a real machine that runs off or AC and can have a pack or two finished building in the time it takes to mod a cheap dysfunctional portable DC powered unit.

I will wait and buy a real machine next month.

Good luck with that.

You will need it.

Skyler.

To be honest its a valid point that most people want to buy something out of the box that works (regardless of what they have to spend)

But equally valid is the fact that there are a lot of people who do know a bit about electronics, and are on a tight budget, who will look for low cost alternatives. Should this work out of the box? Yes of course it should....... Does it, well if you are fanatical about watching your supply voltage, even during the welding then it can, but lets be honest none of us do that. So while the mod is not 100% essential to make a weld if someone can solder one cap in place (which stores enough voltage to ensure the voltage to the control components does not drop during welding then it works).

The second mod of using two batteries is basically that even then (and also with a lot of more expensive welders) the voltage going thru the PCB is too much for a PCB track in the long run, there are mods to beef it up, on this (and on more expensive welders) to make it last longer. On this one conveniently by luck you can use two batteries with no extra electronic work, so that ZAP when welding doesnt go thru that track, but straight to the spot weld electrode.

Is it perfect NO, but nor are some that cost five times this amount, will it last PROBABLY NOT as long as a more expensive one, but its done a couple of thousand welds so far, when you think how long it would take to solder all those joints (never mind potential cell damage) I kinda had my money's worth already and soon it will attempt that again when it builds the next 18650 battery.

I don't expect this to last for a lifetime, but I only intend building a very small number of 18650 batteries, I'm more interested in pouch cells which need a totally different approach.

Keith

And after your initial reaction to this I would be afraid to show you the specialised bit of kit I use on them LOL

To each his own, write up your new welder when you get it, how we learn is swapping ideas and info.

 

[Lucifer]

I saw a new video how to mod the unit.

Cheap 18650 Spot Welder Reliability Mods and Test​

I threw my unit in a dumpster so no mod for me.

I do not see any sense in ordering something that needs upgrades when you can simply order a real machine that runs off or AC and can have a pack or two finished building in the time it takes to mod a cheap dysfunctional portable DC powered unit.

I will wait and buy a real machine next month.

Good luck with that.

You will need it.

Skyler.

Nice Video, he hasn't quite got the knack of using it yet, you could tell by his hands that he wasn't using consistent pressure, there is a knack to using these. Prob the same on many more expensive units (but I have never owned one before). Too much pressure actually makes a weaker weld, too little and you can burn a hole in the nickle, but doesn't take long to get it right, then you just automatically do it without thinking.

It's the same mod in this video as in the one I put up btw, but he didn't have to fix it first, like me he did the mod before blowing it up. Also he didn't use the second two batteries mod (might not know it). But shows it works with just the cap mod, just wont last as long.

Oh and if you can solder (which isn't rocket science) soldering one cap on a board without explaining everything for the camera is literally a 60 second job, you can't count the experimental time finding the best settings you would have to do that anyway, and again explaining what you are doing makes it makes much longer even. SO even imagining you with an Arnold Schwarzenegger mini gun of a spot welder, you would not build two batteries in that time LOL.

But I would hope and accept that a more pro unit should do it quicker and neater.

Keith

PS hope you got a sense of humor............ I at least am finding the image of you dressed as Rambo........... bandana round head........... holding a mini gun style spot welder over your shoulder.......... and then letting it rip on a table full of poor defenceless cells very funny. After the first battery is finished, you can say "I'll be back" and go grab some more cells. Come on laugh

And by sheer coincidence , you now know how to say.......... " Hasta La Vista".... Baby in native Alaskan Inuit. I happens to be the end of the phrase i replied to your first post with, which was "Cama'i tang’rciqamken camiku" which isn't rude BTW, it's actually considered formally polite.

 

[docw009]

Also is seems like the purple single board ones are better and cheaper. They have faster mosfet switching.

I watched a youtube video where they claimed to have welded a copper-nickel sammich, I bought one, and yes, it was quite powerful, easily doing .2mm nickel on my 12V car battery. It blew up after a few more test welds. I ordered a replacement circuit board for $12, and that lasted a bit longer but also blew up too,

I found that there are solder pads for more MOSFET's on the rear of the circuit board, and some users add them. I used to be good at soldering SMT parts by hand. Did it in the lab at work 20 years ago. Can't even see the pads today. No thanks,

 

[rafalg]

It's psychological. I can buy ready made batteries and will not go bankrupt because of that, but it feels great when i build a functional battery for a fraction of the price (and crazy number of hours spent on soldering and stuff). Same with all kinds of diy boards and junk - yep, i can buy a proper charger and be done, but look at this ugly contraption i made in last two weekends - it can charge just as well and cost nothing (except of 100 hrs for making an ugly enclosure). Just a confirmation that im so special and clever...

 

[Lucifer]

It's psychological. I can buy ready made batteries and will not go bankrupt because of that, but it feels great when i build a functional battery for a fraction of the price (and crazy number of hours spent on soldering and stuff). Same with all kinds of diy boards and junk - yep, i can buy a proper charger and be done, but look at this ugly contraption i made in last two weekends - it can charge just as well and cost nothing (except of 100 hrs for making an ugly enclosure). Just a confirmation that im so special and clever...

LOL. On a serious note I am forced to try and save money, but you do get a sense of achievement when you build something yourself.

Don't know if you got IKEA there?? Huge Swedish furniture chain, all flat pack put it together yourself. Analyst now think that a huge part of their success is the fact that people have to struggle for hours to make a simple drawer pack, but get such a fantastic feeling of accomplishment once they finally finish it, that it becomes addictive, "Called The Ikea Effect" LOL

Bit like completing a 10,000 piece jig saw puzzle ......... Why would you do that LOL

Keith

 

[Lucifer]

I watched a youtube video where they claimed to have welded a copper-nickel sammich, I bought one,

Bet it tasted crap, don't think subway will go for it..... Sorry in a funny mood today.


But I see you are wearing out too, getting older isn't that much fun, but the alternative is worse. LOL

 

[scianiac]

I watched a youtube video where they claimed to have welded a copper-nickel sammich, I bought one, and yes, it was quite powerful, easily doing .2mm nickel on my 12V car battery. It blew up after a few more test welds. I ordered a replacement circuit board for $12, and that lasted a bit longer but also blew up too,

Was that with or without the mod in the video I linked?

 

[Lucifer]

Was that with or without the mod in the video I linked?

Assume that questions to docw009 ?

I saw video, and replied above somewhere. If its to me (As it came up in my alert box saying I been quoted, but the quote you replied to isn't mine it's D....9.) but if its to me I don't understand the question.

K

 

[docw009]

I didn't mod my purple welders. Just watched them blow up, I'm too lenient as I didn't bother with a refund. I've gotten refunds on other aliexpress stuff.

 

[scianiac]

It does seem like many of these blowing up is just down the to same design flaw(s) the mods fix. Just poor mosfet driver design.

 

[Lucifer]

It does seem like many of these blowing up is just down the to same design flaw(s) the mods fix. Just poor mosfet driver design.

I'm a bit new to mosfets TBH but from what I can make out if the supply voltage is allowed to drop, they blow, that simple really, so all the mods ..... ETC are basically ensuring that doesn't happen, of course the makers should of anticipated their use and taken it into account, and at least modified the design when the realised what was happening.