DIY Battery Spot Welder - Update & Demonstration 

You sir have just built a time machine! Here's why. Surfing my way through RU-vid, this very video comes into play... within minutes i'm going back in time watching my dear old Granddad build something almost identical. He was an electrical engineer working for the Fawley Power Station. He would make battery packs for stuff he needed at work (No I know they weren't lithium modern stuff) but he also used a much bigger one to spot weld panels for heat shielding. SO on this particular day I was with him in his workshop, when suddenly he exclaimed to himself he needed to spot weld the panel seams.. I had no clue of course what the hell he was talking about as I was only 10. I then, with great interest watched him MacGyver two huge truck batteries with wires and big copper prongs, a few other bits and bobs bolted here and there and within about an hour he was spot welding panels together. This video just sent me back to a fond memory of my Granddad, and his wisdom and sheer ingenuity and resourcefulness. Thank you.

i love the job youve done. im copying it to lern the skill now. i have a tip for ya. im a mechanic. the relay may eventually fail and one of the failure modes is thermal runaway. on my nearly identical system ill build tomorrow ill put a 5.00 dorman 140a fuse between the battery and relay. those things save me on truck systems often behind a relay. cheers and thank you. i did subscribe!

I suppose, this is the best and the most reliable solution I have ever seen. Great job!

Thank you man, I was on the edge of buying one for a fortune, now I am making a parts list! Wonderfull work, great explanation. Not the fist video of your's I have seen, but this earnt my sub.

Wasn't gonna make my own batteries because I couldn't be arsed soldering and couldn't afford a welder. Thanks to this video I think I'll give battery building a go as this seems pretty simple and cheap. Thanks man.

Thank you very much! I had watched several RU-vid clips on this topic, none of them provided good explanation like you did.

Thank you for explaining this man! Im learning more about this stuff everyday, and wanting to make a alternator motor ebike/cycle using a ford 3g alternator (130amps) that ive had laying around for years. Ive got experience building 4 stroke gas motors and bikes (welder by trade), but wanting to get into electric power. Im wanting to build everything including battery, and found your video here. Thank you for going over everything for electric dummies like myself. I have an understanding of starter solenoids from being a backyard mechanic, so this makes perfect sense. Ive even used a spot welder over the years being a welder, but never anything this small. Awesome!

this is the simplest, most effective spot welder, and explanation video of how it works, i've seen. good job, and thank you.

You have explained everything perfectly I’m a trained electrician I love the spot welder kind regards liked and subbed

Very helpful and informative! Probably the best and simple guide I found so far.

Great! Thanks man! Simpliest spot welder of entire internet!

Lots of information before I start to build my own lead acid-solenoid-push on button SIMPLE YET EFFECTIVE SPOT WELDER ! Thumbs up!!

I was about to buy a spot welder from China when I found this video, instead of spending £150 I built one of these using a spare car battery and other bits sitting in my garage. Total cost was about £30 and it works perfectly :-). My battery is a Ford OEM brand rated at 700CCA and i bought a 500A solenoid (same as the heavy duty one in the link). I tried .3mm nickel strip but it was a bit too thick, 0.15mm works perfectly and gives good, strong welds. Thanks for sharing :-).

i made one of these from a 230cca. mower battery, a ford starter solenoid, a 4 ga. battery cable, a momentary push button, a plastic connector block like he uses, and 10ga. single strand copper wire for the contact points. all of the parts except the connector block were used and i had on hand, so total cost for me was about $10 for the connector block with shipping. it works great, with no issues, and i've been using it for over a year. this is the best design i've ever seen. i just quickly tap the button like he does, and presto! a functional weld.

I used the battery out of my car and an old motorcycle solenoid. It literally took 15 minutes to build. Mine's not as clean looking as yours, but it works. Good stuff.

Love U man!!! Just gave this a try this eve with a 19€ bike selenoid, half dead pickup truck battery and junkyard cables and switch! Had a dead Dewalt battery lying around for ages with 3 new cells waiting to replace the fryed ones cos a spot welder costs a fortune! Well, with 30€ and your blessed genious I saved a 120€ battery in a single eve. Jollyest hollidays friend!

Brilliant ! Now we can all have a Spot Welder... Thank you... Today I learned a Solenoid acts like a Relay.. Oh and a Cut Off.. That's excellent...

That is probably the sweet-spot in terms of simple yet effective for a battery spot welder! Gonna replicate this over the weekend, thanks a lot!

Detailed, step by step video of a working project and all the wrinkles ironed out. Thanks for sharing with first class results.

Looks like a great little spot welder, something I have needed for quite a while. Thanks for the review.

Great video and well done. To get more accurate welds, you could program the time the welder is running by fitting simple timer to the welder. I was thinking of a 555 timer ( cheap as chips ) programmed for various mSec settings of welding. The timer switches a beefy transistor (say a 2N3055) that activates the relay. You would have to play around with the welding times to find the optimum settings for the various welds you encounter. It would take the 'stab the switch and hope' out of the current configuration. Stay safe out there.

From all the videos on youtube about Spot welder. This one just nailed it simple and easy to use. I think that's my next DIY project thank you! :)

Wow, not only great videos but you even provide links to get all the gear super fast from Amazon in the UK. Top work buddy.

Simple but better than so called expensive spot welders. Nice job 👏

This worked out very well for me, THANK YOU. Believe it or not, 2 of the 3 solenoids I tried out, didn't even work, so definitely make sure those are working before giving up. What's really important that I would add here is that you have to have the terminal connectors clamped down very TIGHTLY, otherwise the solenoid will seize (not permanently). A lot of us are comfortable using vice clamps but BE CAREFUL - because if you have two (oppositely charged) metal vice clamps sticking up in the air next to each other, that's an opportunity to short the battery while un-clamping and get the $#!+ shocked out of you. Also there is some chatter about using a timer relay switch. Don't bother. The quick tap is all you need as long as the CCA isn't too high (mine is 340). I've also learned that arc-ing is a common problem, resulting in burning through the nickel. This is usually because there is a gap or some 'air' beneath the strip. Two fixes for this is to make sure that your nickel strips are perfectly flattened and to put extra pressure on the offending lead.

You sir ...are a bloody genius and true to British inventors of the past ...just ordered all this on Amazon...I have so many projects waiting for a welder which are to expensive and yours is so cheap and easy to build ...thank you from me and all the happiness my projects will bring now i can make the packs 😀👍

Awesome video again dude! I built one myself from your previous video to build my battery for my electric skateboard, worked a treat, panicked a bit when I read the comments as some safety conscious Steve was rambling about h2 gas being produced, I did it in my lounge an I'm still here but other than that great inexpensive solution to building your own battery pack rather than buying a battery spot welder, vids are great man super informative and helpful, great invention thanks for sharing dude!

Thanks for the video! I built one after studying your design and must say there is a learning curve for applying the welds effectively. I built a 7s26p battery pack using 3.7 V Li-ion batteries. I will say that pure nickel tabs are much better than the nickel plated variety. The plated tin seems to burn through easier. I twisted some approx. 1 mm diameter copper wire together in two strands for each electrode. I found that filing the electrode tips clean regularly while welding helped them not to stick or burn through. I borrowed the 12 V battery from one of our cars for the power source. I charged it with a float charger in between sessions. Your videos were very helpful, so thanks again!

Neat design, this answered a lot of my questions -- FYI: Running a motor or a light bulb from a battery isn't "shorting" it -- since there is resistance between the terminals (even if it's only a dozen ohms, it's still resistance). -- It's not a "short" unless you're approaching zero ohms (which according to ohms law, would try to pull infinite amperage).

Massive thankyou to you pal ive just made a spot welder off your idea and saved pounds just when i couldnt afford it, joys of lockdown, thanks..

Great videos, I'm making one according to your information. It looks like it welds all as good as a factory $200.00 manufactured model. Thanks for the videos.

Your first video was definitely clear enough to understand the setup but definitely appreciate the update

Simple and nice setup. Lead acid batteries only make hydrogen/ oxygen gas as a bi-product of electrolysis that is a reaction to charging/over-charging the battery. Harmless enough just sitting round on a bench though. Also a very simple adjustable 555 timer IC circuit in monostable configuration using a transistor/mosfet to control your solenoid into the uS range.

I get back on this video, to thanks for the idea, it's working great. I'v done it with x20 18650 batteries in parallel, and trigger the electromagnetic switch through another, smaller, 12v battery and it was doing it great. I'v successfully spot weld a large parck of 18650 with it, and everything went super well. So thanks again for the idea!

great video and easy to follow, spot welder working perfect with a 220 CCA battery, thank you for sharing

Your DIY is the most convincing spot welder tutorial on youtube ( I have not found anything better and easier to make). I am still waiting for 4 weeks to crate a suitable one. I have tired with a 45Ahm car battery but the amperage was too much, I have also tried with a motobike battery 12v, 5 Ahm and that welding was quite poor. Now I am waiting for a higher amperage motobike battey ( about 7-10 Ahm). I am about to make an e-bike battery pack for my Bosch 36V bike and can`t wait to have it ready in the meantime gathering old laptop batteries.

Nice and simple it just will never go wrong, well it will fail one day but I love it your springy tips are easy to make with some copper braid and some tubing perhaps I will do a drawing for you so you can see how simple it would be to make then you would have a perfect connection each time as they would be spring loaded Bob-UK

Only brilliant people can develop such simple solutions. Thanks for sharing it

Great video, and just what I need to do repairs to a load of dead Dewalt drill battery packs. You forgot to mention your 18650 battery supplier as there are a lot of suppliers ...some better than others. Any recommendations? Stay safe out there.

Simple & perfect ! Best DIY I have seen for a battery spot welder. Thank you !!!

great video, I happen to have a cheap foot pedal that's very tactile. I find using my big toe for the button and having two hands-free woks quite efficiently ;)

The best guide ever uploaded on diy spot welder dude! Your amazing!definitely gonna order the pieces and build one!

Thanks for the upgrade info as well as the failures of burnt strips if contact time is excessive. I made a crude set-up which had partial success. Copper nails may help. Timing is the key. J K

It's great that you have kept everything so simple and it works. Screwfix or Toolstation do a 30A ceramic block connector. That nickel strip will glow white hot at hundreds of amps for a long time. It is the ohmic area(lots of routes probe to probe) resistance, it is not a fine wire! Spot welding is 'resistance welding' - if there was a short circuit then it wouldn't heat up. The probes provide a localised area of contact with high resistance. For the minimum safety instead of just trying to tap the button = I suggest a simple circuit of a resistor and a capacitor that charges up to 12v, then your switch button connects that to the solenoid coil. If the pulse is a bit short, press again.

Nice build, I have built the same setup but I added a timer to the switch which is foot operated. I have timer set to lowest setting which is 0.1 second, this works out perfect every time. My only problem at moment is my leads are not thick enough and get hot with prolonged use.

Great video and I have made up my welding rig pretty much like yours. I've made one slight alteration in that I have used a lever moment switch which gives a much more consistent connection as you flick it and get a consistent weld.

The ideal solution for a tab welder is to deliver an exact amount of energy every time to the nickel strip to weld batteries. You can do that manually or electronically by charging a bank of capacitors to a precise voltage level. The energy is equal to 1/2 times the capacitance times the voltage squared (.5CV^2). So, use battery to charge caps, disconnect battery, then close switch to weld.

Great video and got me welding batteries like a king! I am using bog standard cable and a tray of ice to cool the tips. Works perfectly, your massive cables are just conducting heat from the tip rather than the current.

I am going to give this a shot. Already purchased 1/2 of the items.

Superb. I tried building one and it worked like a charm. Thanks a lot... 👍🏻

its a great setup u dont need a timer you have plenty of power just hit it quick n bam its done great job

BTW, your 1st video was top-notch for anyone that has a basic understanding of electrics. To be honest, anyone who starts banging on about exploding batteries etc., really shouldn't be attempting anything but adjusting their Warrior® armchair height, ffs! Anyway, I've not made a spot welder yet, but I was pondering whether using spark plug electrodes would be the way to go? Most have suitably sized platinum-coated tips, and are designed to last for bucket-loads of sparks. Smash the ceramic insulator off, and Robert is you father's brother! Also, I'm wondering if a 3-way automotive toggle switch set to [OC~SC~OC] would be a good way of getting the solenoid energising time perfectly tuned? As you throw/push the lever from open circuit through closed circuit, and on to the opposite open circuit. The short time that the lever closes the contacts as it passes over might be perfect?

You could use Tungsten rods for TIG welding instead of copper nails xD

So when u press the button doesnt all the 300+amps get dumped into the control wiring? So the button and the small wiring all run300 amps while they are not supposed to. Amirite?

Doing it like this makes doing it any other way look dumb.

Just built one...Works great.... Thank you for the detailed walk through

excellent craftsmanship, nice low-cost project. I appreciated the copper nails really a great idea ....... ty

I just built this, it works better than my Sunkko 787a+ on 18650's, tomorrow I’ll try the 26650's double thickness. I used a rocker arm to keep the wiring tidy and mounted the switch on it which adds weight to the electrodes but otherwise identical, Great video.

I don’t think a two to one mix of hydrogen and oxygen are toxic... just highly explosive. Great video and project description! Bought a solenoid the other day at my local auto parts store :-) have a few good salvaged/gifted automotive batteries in good shape in the 600-800 CCA range, old jumper cables, and a box of heavy wiring connectors I’ve built up over the years from various projects. Need to build one of these! Hopefully the high CCA batteries won’t be “too much!”

Nice project. Thanks for sharing. Just a quick thought. You could also insert the copper nail from the top side keeping the head on. Now you can spring mount the nail using tiny spring on top of the nail head. Because there is a little room between the two screws that are holding the terminals in place. Thanks again bro. Keep them coming.

Like your Spotts, Just an idea/question re doing 4 spots in one go ie using 4 copper nails with a spacing insulator (maybe four holes evenly spaced in a bit of wood to start with) just a very little extra wiring to 4 terminal blocks? It sounds like the battery could handle it OK ???. Nothing like cutting work in half. I think your return spring idea could also work better using a bigger four-pronged foot.

Awesome video. For a beginner, this was very helpful. Thanks.

That's pretty good. Why are we paying 100$+ for arduino welders when we can just make one of these... Thanks for the informative video...

I would make sure you have a good battery. I was working as a mobile auto mechanic and a older woman called to her house because her car would not start. I stopped by and her car was in her open garage. Now the hood was closed and I did not see any charger around. She told me she tried to start the car several times that morning but it would not do anything. Hearing this I decided to confirm the failure by trying to start the car myself. With her standing by the car and myself in the driver's seat I turned the key attempt to start. Instantly a big blam, dent in the hood, acid fumes coming out from underneath the hood and luckily the hood didn't open. Luckily she was there to see it or I think I would have some hard explaining to do. Yes I never seen anything like that before or after. I asked if she charged the battery before I came but she claimed she did not. After hosing out the engine compartment I removed the battery and replaced it everything worked fine, no overcharging or anything. All I can say is make sure you have a good battery and that if it is not sealed type, has water in all it's cells, has not been changed for several hours, you should be safe. Also have the battery tested too. Never figured out why that battery exploded or why it did not for the older lady.

This is a good Brute Force welder with proper amperage! None of that fancy electronic bs! Hehe

As soon as hit the SpotWeld Button I hit the LIKE button ,great video thanks

Thanks great video, everything clearly explained. One warning, not a good idea to work around batteries, especially high power ones wearing a metal ring. If you short out across the ring it can get red hot before you really notice and then you can't get it off before you loose the finger. Doesn't happen often, but a few people loose a finger that way each year.

Wanted to thank you for posting this build - I'm just getting into welding my battery packs for a project I'm hoping will have some retail value. I had a spot welder from when we built tube-lights for ye olde 70's disco floors but it's pressure triggered with vertical poles. Easier to DIY from scratch than try to reconfigure a 40yr old spot welder for something that may not even sell.

"Nothing sinister" Haha, man, I'm going out this weekend to get a battery and the other parts. I'm glad I waited for this update because I was only going to get a 200A.

Great video, thanks for sharing your knowledge, you explained it in simple terms so someone as thick as me could understand

Nice update thanks..

Have a Solenoid, Bat, and everything but the switch,, lot better than $300. 00 mini spot welder,,,Thanks so much, Great updates on your videos,, Thought about doing it by just hooking a Bat. up to two pins, and just touching the strip, love this way much better,,,

OK..I got it to work now. The battery CCA should be around 250 - 400. I change my battery from 800CCA to 310CCA. It work greats now, also the nickle strips needs to be real 99% pure nickel not plated. I had some plated strips mixed into my supposedly pure nickle batch and they did not stick at all to the 18650 battery. The real nickle strip were very easy to spot weld and held firm! Also I found an easy way to spot weld is to put a small strip of solder under the strip(for plated nickle strip only). I angled the tips and let it do the quick heat spark and it melted the solder and welded the strip to the battery really fast and hold firmly too! This process made the welding stronger and easier.

Thanks to you, I'm building a 5V-10V super cap spot welder. Thank you so much for the idea.

Well, now I'm regretting not grabbing that solenoid from the junk yard last night..

Another great video!! I'm definitely going to make my own diy spot welder like this one. Thank you for the step by step instructions how to do this. Thanks and take care. Aaron

You can add a 200 amp fuse, just in case if the solenoid get stuck.

After two months of search on youtube I come cross with your videos. I found your videos very useful, Clear, simple. You describe functional and cheap to built device. What else we should be looking for more... THANK YOU for your knowlewdge and experiments that you shared with us darkkevind. I already ordered my components to built my own spot welder very soon.

I love this video pure genius with very few components to go wrong great video unlike other videos on RU-vid with cheesy music

20:40 screw it up, and you're done XD

This guy is a true genius!

How about a wireing diagram. Thanks.

12V 35Ah 330A must be a UK thing. In USA, the search engine always converts A to Ah, and all the parts stores know how to do is add what car it's for into their system. None of the batteries on display show A ratings. Anybody here in the states who can help? Some truck batteries list cold cranking amps, but they usually start around 800.

Improvement Idea. I might be wrong. Add a little 12v relay. And a capacitor 4700uF or just try different values whatever works better. If you know current draw of solenoid you could prolly calculate the exact value you need. When switch is pressed it turns on relay. Relay connects positive (or negative) through capacitor to solenoid. It comes on and goes off when capacitor is charged. And use NC point of relay to short the capacitor to discharge it when switch is depressed. Hope i was able to explain my idea

If you need solenoids explaining not sure you should be making battery packs quite yet sorry 😐

If you get a large value capacitor (say, 1000uF) and a 1k resistor and put them in parallel, then put these two in series between the pushbutton and the solenoid, then you will get a short pulse.

Excellent, thanks for your detailled descriptions and explanations !

Great setup. Very simple and inexpensive.

thanks for the video really nice and simple put. but i seem to have a problem.i have the exact same battery same setup but i use slightly large gauge wire and copper nails and i get huge sparks it burns 2 mm holes in my nickel evey time. because of this i bought the same cable you suggested yet the cable linked to amazon is a 16mm cable and looking at your setup yours is not 16 mm so im a bit confused because i have the same choc block but my cable would need atleast 3 of the strands removed to fit. whats going wrong do you know? are you cutting wire strands from the heavy duty wire to fit it in the block? possible amazon sent me a smaller size choc block.mine is x24mm,y24mm or so with a hole of about 5.3mm is yours the same? thanks allot for the build.

In need of new 18650 packs, I built one like yours last night. Just wanted to say thank you. Previously, I made a spot welder from a old 900 watt microwave that regrettably let a friend borrow. He said he let someone borrow it and that guy disappeared with it, lol. No more loans to anybody from me ever!

Flippin amazin... Was looking at. Spot welders with dismay coz I'm skint.. This perfect... And perfectly explauned. Thanks

Awesome, you went above and beyond explaining everything, just what i needed to make one 👌👍

I had collected loads of batteries but could not figure out how to get a spot weld. This is fantastic. I don't know why I am only finding this now after years of searching for a simple diy method. In regard to the switch. did you consider having a capacitor and resistor to control the timing. I think a simple circuit like that could work. Perhaps in combination with a transistor.

Greetings - thanks a lot for such a detailed explanation ! I am not knowledgeable in electricity so I have one naive question if I may : why a solenoid rather than directly putting a switch on one of the cables between the battery and the welding rods ?

Good job on the video, thanks for the information from across the pond!

This is awesome! Love the simplicity. Just to add, I think a car starter pulls more amps when cranking the motor than this welding thing.

Love it! Only thing I'd probably add would be an arduino timer that you could program the length of the relay engage cycle...and maybe a secondary relay wired up as an emergency shutoff if the first relay stays on too long. (if the arduino is fast enough that is).

Very simple and effective. Well done! What you are doing is safe, but just a couple of corrections to your commentary to help others keep safe. The gases from lead acid batteries are not toxic but are explosive - so ventilate well when charging and don't do any welding for a couple of hours after charging to let the gas disperse. The battery WILL GAS WHEN DISCHARGIING HEAVILY ie. when welding! However, in a sealed AGM battery or even a low maintenance battery, this is unlikely to be a problem in this application. to be on the safe side do your welding in a well ventilated area and even use a fan to blow the gases away from the weld area. If you are using old fashioned flooded batteries then definitely think carefully about dispersing the gases (hydrogen + oxygen). A little common sense and understanding of what you are dealing with is all you need to stay safe - enjoy.

Cheers mate, I'm a newbie to your channel, I was looking for a how 2, and you gave me the guidance I needed 👍👍👍👍

having watched this video i built one, went to a car dismantlers for the battery, they sold me one for £20 with 550CA , rest of parts cost about £20 so in total cost me £40. have built 2 batteries so far for 2 friends they are very happy and look much better than my soldered battery, also soldering on wires for a balance board was much easier onto the pure nickle strips. Thank you is this vid that made me try