I put premium fets in mine and it still made random burn-through welds. I figured it was the circuit but Fabio's capacitor mod solved it. New fets are safe. RIP original Chinese fets. You were not to blame for what was done to you. 😥
One thing I found with this welder is that if you do not press hard on the strips (rather just touch them) the welds are much stronger at lesser 'ees' (due to the increased resistance at the probe to strip joint of course). I can blow holes in my strips (single strips) at 40E just by making an awful connection between probes and strip.
Adam and Fabio thanks !!! You gave me hope to fix my cheap Chinese spot welder. I only change mosfets but it not working, still smoke... Now I know what I must add :) Best regards from Poland.
@@AdamWelchUK the ones you have will be much better, I saw a video of a guy hacking his smart BMS with better mosfets to handle up to 300 amps from 40. I’ll link it if you want to see it?
Thank you for sharing. So lovely to fix what many others would have sent to landfill, not only for this great environmental gain, but also for the learning & understanding that came during the repair process. I have one of these units but I have been fretful to try it & now I can go ahead knowing a lot more & with some super useful mods. This type of hugely helpful video is what builds the internet & brings us all together for mutual benefits as a species. Thank you!
Mine also blew the centre mosfet. It shorted and blew a big hole in the bottom of the battery. I was running out the house hands, hair, and 18650 on fire like cracker night. Ebay seller gave me money back and i binned it. Then I saw this video, after an hour of bin diving, i returned it to the workshop bench removed shorted mosfet and now happily weld away:)
I saw a spot welder review that gave the impression that the more mosfets used, the better it welded. Would it be easy to add more mosfets (stacking?) and would it break the electron equation by adding more mosfets in parallel. Also, could two 12v batteries (in parallel) be used instead of a super-cap to increase the available amps to the spot welder? great repair and hack/fix btw, thanks for doing that.
These mosfets are all in parallel and you could increase that number yes. Physically doing that on this board wouldn’t really be possible because you need the mosfet to sit on copper to achieve the cooling. Adding more mosfets increases the potential maximum current of a circuit, but doubling the mosfets doesn’t necessarily mean twice current. Also mosfets of the same brand may still have slightly different characteristics and therefore one will always take a little more current than another.
Next mod: double-pulse weld! This is done in higher-end units (that is, >$25) -- the first pulse "cleans" the contacting surfaces, the second pulse accomplishes the melting and fusing of the metals. Can we have access to the processor for a firmware upgrade? Are schematics available? Or simply replace the foot switch with a circuit that pulses twice? (a couple 555 timers, or something more arduino-ish)
just got one from Amazon, but it does not have a diode on the control circuit all. Can you let me know which vender from AliExpress you purchased it from?
Hi Adam - be aware how much you press down will affect the weld, after all its a resistance weld. IE too much pressure and the resistance between the 2 strips will be too low. Using 2 hand held probes just use a light pressure, and be consistent from weld to weld to achieve consistent results
@@AdamWelchUK It's a modification that shouldn't have been necessary if the design was properly tested before it went into mass production. I must emphasize that the health and cold cranking amps ability of the battery is paramount! Washed up lead acid batteries just won't do. I use 0.15 nickel strip at 20E, the welds are perfect.
I think the E is for joules, I. E. The amount of energy used for the weld. Will basically be how long to maintain the short circuit, with the assumption the battery voltage doesn't drop (too much).
Good result mate. Just in case you aren't aware, the MOSFETs gate is extremely sensitive to ESD. Super easy to damage even if you don't feel the static discharge.
Hi Adam, thank you for steering us in the right direction. I have browsed many tubes and have circumtubed you once again. And my thoughts were as follows. WHY THE HELL DOES THE QUEEN NOT FOLLOW YOUR CHANNEL? And if not, I would grant you to be... The Knight of the round thing and blinking stuff, with gadgets and electronics to amuse her majesty :)
Mine is still going strong, used it to build a 14s 680p 1222ah 18650 pack. no issues. but alot of my viewers had problems with theirs. So thanks for this video. I been sending them here for the fix.
Very good - I think the super capacitor bank across the battery (or any power supply - an old PC power supply for example) would work well with this welder. Can you check the before and after volts of the bank after a weld with just the super caps Julian?
Adam, thank you so much for testing this out. I´ve modded mine also today but i was a little bit scary to use it :-P I also upgraded the bars with 2.5mm² coper wire....but the idea to conntect both psitve lugs to the same spost is just brilliant! THX to the gut with that idea! Have a nice holiday
I purchased a unit in Dec 2020 and was about to do your mod but discovered they have fixed the problem by putting a diode in series with the 1000uF (big green cap on MOSFET board. This capacitor now feeds all the electronics including the MOSFET drivers. So power supply can dip to zero volts during pulse and MOSFET drive remans at 11.5V during the ON period.
I'd caution against directing people to Aliexpress, eBay, Amazon and any other similar websites when purchasing semiconductors. Unfortunately there's a major problem with dishonest sellers distributing fake/counterfeit parts. As a general rule, it's best to purchase from an authorized vendor whenever possible. Kudos on the repair AND improvement. Having gotten a better look at the guts I may end up buying one of these for an upcoming project.
300 A is quite a lot of electrons! It is a typical starting current for an engine and lasts several seconds. If anything the battery is way too large for the lask.
Hello, this reaction might be a little late but how did you determine which mosfet it is? And what if i don't get a continuity reading but when i switch the probes i do? Regards
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.
I've got exactly the same issue, down to the 1st attempt and identical scorch marks in my wooden bench. Mine came with 2 spare mosfet so I reckon I need to do this. My initial issue (I think), is also power supply related. What's the best battery or power source and what are the parameters for a got power supply? Many thanks. 👍
I have one of these. Did the cap mod straight away. Also loaded up the tracks with more solder and shortened the cables as much as possible. Works fine on 0.15mm strip and a nice chunky car battery. Tried a 5000mAh 70C Lipo but it wasn't as consistent. Ended up making my own spot welder using a rack of mosfets controlled by an Arduino and it'll weld up to 0.4mm strip. Will happily weld a 13S 14P pack of 18650s start to finish without even getting warm. Weld time adjustable from 1ms to 40ms.
@@TYGAMatt Hi TYGAMatt. Sorry I don't know the best way either. It's not a good idea to make email addresses public. I guess I just need a bank of very low on-resistance high current MOSFETS an Arduino timer adjustable from 1ms to 40ms with a buffer to drive the gates. I can't think of any other smarts that should be included in the circuit. You may be able to suggest some. Show less
@@jamesgordon8960 yes, I used ten mosfets in parallel driven by a TC4420 mosfet driver. A couple of big ass rectifier diodes to stop and naughty spikes after firing and also a couple of TVS diodes to clamp any excess voltage. An ATtiny85 is the brain. Not much to the code to be honest. It just senses a connection from the positive probe through a voltage divider into a digital pin, and then does the firing. Its a twin pulse, so a very short 150us pulse, then delay followed by the welding pulse which is adjustable as I said from 1-40ms by twiddling a potentiometer. Have a SSD1306 display just to show the pulse time. The code is all port manipulation to ensure the fastest speed. To be honest, the actual hardware just follows what I found online on various forums with a couple of tweaks. The code is mine but nothing to it really.
FYI the new version of this spot welder which I just received has this problem fixed: they moved the FET pilot circuitry on the main board and used the onboard 1000uF cap to limit the Voltage drops so the fix is no longer necessary!
I just bought one that had the new version and the middle MOS tube burned out on my 3rd attempt at 30E pwr. I was using a LiPo 5000mAH, 3s, 90 C-discharge, w/ a XT90 batt connector. For the life of me I can't figure where I went wrong and why it fried so quickly. Any thoughts, would be greatly appreciated.
@@ttttenney was it this one: th-cam.com/video/VQR9cTcP5Bo/w-d-xo.html They implemented a fast gate switch off mod also, I checked with my scope using a limited current PSU to see if the gate voltage would drop but it didn't so that problem is definitely fixed. I did a few welds using a small 12V 20Ah AGM battery (45Ah is suggested but I have a CCA battery tester and that one gave well over 240Ah) and all went well. I suggest you clamp the 2 positive wires on the *same* positive lead to avoid any further losses (no need to go through the PCB track for that) and be sure you have good contacts. Having said this, when a FET fails usually it is the one that either has less GATE voltage or has most internal resistance (least efficient). If you remove the blown/shorted FET the welder will still work though with limited current handling but should still be able to test weld. The reason they are using many FETs in parallel is not because of FET current handling reasons but for internal resistance reasons (the more in parallel the less internal resistance but the more prone they are to be unbalanced as they ought to be all matched perfectly which is near impossibile plus their capacitance is increased which is why you would need a proper FET driver). Just be sure you batteries are well charged and can deliver the CCAs (at least 100Amps) and that your connections are solid. Of course it could very well be that you were unlucky enough to have a mismatched FET!
@@Luca_Techy your detailed response and link were more than I was expecting, so thank you. Yes, mine was the exact one shown in the link, which is even more surprising as to why the MOS tube burned so quickly. I'm an RC guy with lot's of mAh / cell variations of LiPo's on hand, and I understand the importance of good solder joints and contacts. The LiPo I used was newer and fully charged, so again that's why I'm so confused. Like you suggested, I also de-soldered the the burned out MOS tube and tried again, but it just didn't have enough umph for my .15 Nickel strips, even at full 99E. I've got another one on the way and will do what you've suggested by connecting both + wires to the same terminal. Like you, I also have a 12v 55Ah AGM, which I use for my trolling motor and will give it a try with the new one. Thanks again.
@@ttttenney There are also other issues to fix such as adding an inrush resistor in series with the cap diode. Check out my latest videos on the matter before using it!
I am a pretty green with.ic's and what not. although I have learned NEVER skimp on flux. weather installing or removing. I can see you have oxidation,flux will fix that and also help transfer heat better! I am just getting to figure these hings out more and more! .Hope it helps. though this is 3 years old? OI also use a normal brilo pad , along with tip tiner. keeping the tip covered at all times is key to not needing to 86 your tip and loose interest in soldering all together like I have in he past!t only thing is cheap store bought brilo oxidase fast, they are dime a dozen though!~ if I ever get round to it I will get a nice cleaning kit...
i had a similar issue and had to add more solder to the the pcb board to help to carrey volts as the pcb board fails to carry the volts more volts and has help or can add a bit of thick copper wire
Hi you showed that with your blown mosfet, it had blown closed which showed as continuity, how would you check for one that has blown open please? Many thanks for your Help Guys!!!!
You disconnect the power and find the GATE (single pin), Cut the track or unsolder and lift it, leaving the Drain and Source soldered. Now you must discharge the gate - short circuit the gate connections to ground (negative). Use multimeter to measure the resistance between Drain and Source - should be open circuit. Next, touch the gate with your finger which will slightly charge it. Check resistance from Drain to Source and it should be a very low resistance... that means Mosfet is working, re-connect the gate.
Thanks for the heads up. Your shortened explanation is a bit confusing, though, because: If I understood Fabio correctly, the problem actually does lie in the control circuit. In the control circuit not having enough power to keep the MOSFETs' gates open. That's why the fix is done on the controller's side.
Do you know what thickness of nickel you were using? I am considering buying this welder and getting some .15 nickel to fix up power tool batteries... tho I may splurge a little more and order the malectrics spot welder I just wish I could find one of those available in the US
Mine just blew up, but for a different reason. The one I have is a newer revision (bastards etched off all the part numbers!), on mine the entirety of the gate drive circuitry and controller are powered by a massive 10000uF capacitor fed via a series diode. The gate drive is sent through a 100 ohm resistor to what I think is an NPN transistor wired up as just a basic inverter (common emitter). That feeds what looks like a standard totem pole arrangement of BJTs and a bank of 30 ohm resistors that drive the gates. Mine blew up after a few weld attempts, too. Mine does not have the diode on the secondary logic board but instead a small LDO in it's place. I verified with a scope the voltage does not sag (with a current limited supply and the output shorted) so this mod was unnecessary. However I think I figured out why it blew up: the 30 ohm gate drive resistors are absolutely tiny, I think they were 0603 or even 0402 parts. they were all way too high resistance and under a microscope I could clearly see they were blown! I replaced them with larger 0805 20 ohm resistors from digikey. Really I think 1206 would be in order for these ones. Would have also preferred to see a proper gate drive IC rather than a dodgy implementation with generic discrete transistors. Unfortunately I think now something is wrong with the controller, it does not appear to send pulses to the gate drive circuit and does not seem to register presses. Also I'm curious why they chose to invert the signal to the gate drive, as when the controller boots up the output is enabled until the MCU is up and running which seems like a design flaw, it certainly caught me off guard.
Top tip, through away the module and just use the leads to manually use it. Only got mine yesterday and didn't manage to do anything but blow holes in everything and explode an 2016coin battery (with flames). Thought i was maybe not giving it enough current as display was dimming, then accidentally joined two motorcycle batteries in series rather than parallel and blew the fets. After abandoning it i have already welded a couple packs together with no prior experience of battery tab welding. Hold one leads contact down firmly and tap as quick as you can with the second leads contact, then I reverse leads and repeat. Quickly learned that if there is any air gap between the nickel strip and lead contact it will blow a hole in the nickel.
Hi, i have the new revised model and this one also burns mosfets, apparently you need to change a resistor this time, i did that and it keeps burning mosfets. Looks like it keeps the current open for too long.
Using too weak of a battery could cause the voltage too drop during the short few milliseconds of the welding process to the point where the gates on the MOSFETS to be only partly open and not close properly. This will cause the MOSFETS to blow.
hey Adam, do you know where to get "thick" 0,3mm x 8mm wide nickel strips? I prefer pure nickel its for high current application. Right now I just use 0.12mm strips, that is fine but I have to tripple it up, my welder can do it - its a Kwelder so. To save time.
3h ago I got mine from Amazon UK (August 2021) and the board looks identical as on the video and it does not have the cap. Haven't tried it yet as I am still waiting for the nickel plates.
You could hook up a power supply to run the MCU separately to the battery so it didn’t suffer the voltage drop. I don’t know if a power supply would suffice, I’m going to do my best not to blow it up when it arrives so I probably won’t be experimenting.
You'd need an absolutely MASSIVE power supply, something that would cost a lot more than this shitty little welder. There are far better ways to make these if you are willing to invest $$ rather than the cheapest possible solution.
When you're faced with that much solder to de-solder you'll need a hot air gun. With a temperature set to some 270 Celsius, just hover around the failed mosfet until the surrounding solder starts to melt, while your other hand holding a pair of SMT tweezers ready to lift it off the board. Once done, clean around the area a bit, place the new mosfet and heat up the surrounding solder again until it melts, add some flux to it to help the solder adhere and smoothen and the component will sit itself on its pad. Voila!
Have not seen a schematic for one of these but have a question about the FET's. How does one get an FET to work with only 2 circuit connections? I see that the components have multiple terminals yet there are only 2 buss connections on the PCB. At least it appears that way from the video.
Does your fixed welder always read 12V across the welding tips even when not welding? I made the cap modification, when I try to use the device regardless of manual or auto setting it does a small spark when touching metal and resets (powers off then on again.)
Can i use a 12v 60amp SMPS. As the retailer suggested that i can use this spot weldet with 12v 40 amp SMPS. Should i use an smps? I have made the capacitor mod as per fabio specs. Please help me. Thank you
Got mine a few days ago and used one of those car battery jump starters that I bought from costco uk. The specs were starting current 200A and a peak current of 400A. I was hoping this would work but I ended up blowing the large capacitor. What battery do you recommend using with this?
Take a proper battery, 3s 5000mAh LiPo 50c or a 12V 40Ah lead acid car battery and you are happy without doing any mod´s of the spot welder. This thing is working fine without any problems only by using a proper battery. Also you can weld 0.2mm nickel strip at 25-30E setting.
This is simple request but I’d like to see one prob on battery then second probe on strip. I’m thinking current should flow thru the strips from top to bottom not sideways. Just a thought. Mines coming Wednesday I’m gonna try both ways. I used to spot weld sheet metal and current had to pass from top (positive) thru to bottom ( negative).
I bought this spot welder. Will it work with a 4s lipo at storage charge 15.3v? I was thinking about running a few of them in parallel. They are rated at 75c
It was added because my ageing (and fairly small) lead acid battery may not be able to deliver the current or needs to. I’m yet to try it without the super capacitor to be honest. I probably should but I don’t want it to break again!
@@AdamWelchUK Looking at the battery you have, looks like an SLA battery of about 17 or 18ah used in UPS units typically. New they can discharge about 230amps but they also have a low cycle life so you're probably well under that now. If you have a second one I'd double it up or maybe pickup a lawn tractor battery, they are usually about 30-35ah and can discharge 300 amps pretty easily and are pretty cheap in the states, about $30 not sure where you are at. I just ordered one of those welders but I'm going to use it with some lifepo4 headway cells that can discharge 200 amps continuous since I have them already. I'll add the extra cap for like you did for safe measure to it.
I have a 5000 mah 3S 60P lipo I just picked up and this spot welder. It makes the noises in auto mode but nothing ever actually happens. Both the welder and battery are new. It says use up to .12 strips but at the moment I have .15 and am wondering if that's the issue.
Mine was a slightly updated version. After hearing everyone say you need a good battery I pulled the battery from my truck. First spot weld at 05 was very weak, so I changed it to 10 for the next one. This made a very good weld, but on the second weld it blew a mossfet. I followed someone else's advice and removed the blown mossfet. Next attempt was set to 10, first weld was perfect, next weld blew another 2 mossfets. Even with a good battery its still a crap product.
I removed burned mosfet, have 4 Mosfet in it, now I use two lipo batteries (3S 5000mah 35c) in parallel, and it welds at 5E perfectly, after 60-80 continuous welds - it slightly gets warm.
Being a HVAC sheet metal mechanic (tin knocker) many years ago I used a rather large bench top spot welder, pushing down on the lever it "pinched" the two sheets of metal thus compressing the point of contact giving it a good mechanical "bond" and switching the transformer on and creating a good strong weld. This is what you have to do to have a better spot weld by pushing down a little harder on the probes, it appears that you're just touching the point of intended weld - not good enough. And lets face it, most of the problems you're having is the lack of current, just go out and purchase a small car battery.
Thanks for mentioning my video, it s probably thanks to this i ve got many views, and this useful mod spreads around
I love that there was a failure first then a modification was made to make a success. Thank you for this.
I put premium fets in mine and it still made random burn-through welds. I figured it was the circuit but Fabio's capacitor mod solved it. New fets are safe. RIP original Chinese fets. You were not to blame for what was done to you. 😥
What fets did you use, or what rating did they have? im thinking of DIYing this if the fets don't cost a leg and a foot
One thing I found with this welder is that if you do not press hard on the strips (rather just touch them) the welds are much stronger at lesser 'ees' (due to the increased resistance at the probe to strip joint of course). I can blow holes in my strips (single strips) at 40E just by making an awful connection between probes and strip.
Literally happened my time to me and the solder traces gets too hot
Adam and Fabio thanks !!! You gave me hope to fix my cheap Chinese spot welder. I only change mosfets but it not working, still smoke... Now I know what I must add :) Best regards from Poland.
Mine had a couple extra FETs in the bag, I guess they knew I'd need them, ha-ha, happy holidays!!
Really? You could have got a tenner for them! ;-)
@@AdamWelchUK the ones you have will be much better, I saw a video of a guy hacking his smart BMS with better mosfets to handle up to 300 amps from 40. I’ll link it if you want to see it?
@@MistaTerps please link, thanks!
th-cam.com/video/9B6_EC85ib0/w-d-xo.html Merry Christmas.
mine came with 2 also..
As more commenters, I didn't expect to weld that well! But I'm glad this story has a happy ending. And thanks to Fabio for this fix!
Yeah I was pleased with the results. Cheers Dustin.
Thank you for sharing. So lovely to fix what many others would have sent to landfill, not only for this great environmental gain, but also for the learning & understanding that came during the repair process. I have one of these units but I have been fretful to try it & now I can go ahead knowing a lot more & with some super useful mods. This type of hugely helpful video is what builds the internet & brings us all together for mutual benefits as a species. Thank you!
And thanks to you for your lovely comments. :-)
Mine also blew the centre mosfet. It shorted and blew a big hole in the bottom of the battery. I was running out the house hands, hair, and 18650 on fire like cracker night. Ebay seller gave me money back and i binned it. Then I saw this video, after an hour of bin diving, i returned it to the workshop bench removed shorted mosfet and now happily weld away:)
Wow, glad to hear you survived that!
Thanks Adam, I replaced all Mosfets with 300A 12V Mosfets, it works great on 5E
Sweet! Turned out to be an “Expensive” super cheap spot welder !
LOL. yup. he could have got the rechargeable good on for what he has into this. although he will likely get a refund like I did.
Spot on Adam, great follow up, although I am enjoying all the videos of people smoking them.
Glad you got it working. I caved and bought a 5000mah 3S Lipo for about $25 from Amazon. Just have to buy some larger connectors.
Great. Good luck.
Glad to see you decided to repair it and get it working great show of that fellow percy virance :-)
Are you not sepost to have the probes of the welder on either side?
18:18 Aaah nevermind
I saw a spot welder review that gave the impression that the more mosfets used, the better it welded.
Would it be easy to add more mosfets (stacking?) and would it break the electron equation by adding more mosfets in parallel.
Also, could two 12v batteries (in parallel) be used instead of a super-cap to increase the available amps to the spot welder?
great repair and hack/fix btw, thanks for doing that.
These mosfets are all in parallel and you could increase that number yes. Physically doing that on this board wouldn’t really be possible because you need the mosfet to sit on copper to achieve the cooling. Adding more mosfets increases the potential maximum current of a circuit, but doubling the mosfets doesn’t necessarily mean twice current. Also mosfets of the same brand may still have slightly different characteristics and therefore one will always take a little more current than another.
I bought this welder but didn't use it because I knew it had issues and would blow up. Thanks now I can do the MOD and happy it should last!
Next mod: double-pulse weld!
This is done in higher-end units (that is, >$25) -- the first pulse "cleans" the contacting surfaces, the second pulse accomplishes the melting and fusing of the metals.
Can we have access to the processor for a firmware upgrade? Are schematics available? Or simply replace the foot switch with a circuit that pulses twice? (a couple 555 timers, or something more arduino-ish)
Don't you have to wait for the system to recharge before the second pulse?
@@johnaweiss no its instant and it can be done with a high current relay and a control board you could even make a add on board
just got one from Amazon, but it does not have a diode on the control circuit all. Can you let me know which vender from AliExpress you purchased it from?
Hi Adam - be aware how much you press down will affect the weld, after all its a resistance weld. IE too much pressure and the resistance between the 2 strips will be too low. Using 2 hand held probes just use a light pressure, and be consistent from weld to weld to achieve consistent results
Wow,I didn't expect a follow up so quick😀
I couldn’t leave it there :-)
@@AdamWelchUK It's a modification that shouldn't have been necessary if the design was properly tested before it went into mass production.
I must emphasize that the health and cold cranking amps ability of the battery is paramount!
Washed up lead acid batteries just won't do. I use 0.15 nickel strip at 20E, the welds are perfect.
Boss, I want to know what name items are exhanged
Fabio’s video showed up on my suggestions after watching your video. I was think you will probably get to it eventually.
Glad it’s working again.
Well done Adam i am curious to see what the battery voltage is during a weld. Is the adjustment you are making for voltage current or time?
I think the E is for joules, I. E. The amount of energy used for the weld. Will basically be how long to maintain the short circuit, with the assumption the battery voltage doesn't drop (too much).
I heard in fabio video that it is milliseconds, but joules are perfectly logical too.
Well done on fixing the spot welder. I was hoping that you would work out a solution.
Good result mate. Just in case you aren't aware, the MOSFETs gate is extremely sensitive to ESD.
Super easy to damage even if you don't feel the static discharge.
Hi Adam, thank you for steering us in the right direction. I have browsed many tubes and have circumtubed you once again. And my thoughts were as follows. WHY THE HELL DOES THE QUEEN NOT FOLLOW YOUR CHANNEL? And if not, I would grant you to be... The Knight of the round thing and blinking stuff, with gadgets and electronics to amuse her majesty :)
I’m expecting to be on the New Years honours list soon. :-)
Really enjoyed your video Adam, so clear and easy to follow,...look forwards to the next one, Cheers
I KNEW you wouldn't leave it alone!
Mine is still going strong, used it to build a 14s 680p 1222ah 18650 pack. no issues. but alot of my viewers had problems with theirs. So thanks for this video. I been sending them here for the fix.
Why isnt yours burning up?
Thank you, will try same mod. Waiting for replacement mosfet to arrive. Mine also blew up shorted.
Very good - I think the super capacitor bank across the battery (or any power supply - an old PC power supply for example) would work well with this welder. Can you check the before and after volts of the bank after a weld with just the super caps Julian?
Great little spot welder as long as you use the correct battery
Thanks for the indepth explanation i purchased one from amazon with capitors aswell did your mods today well impressed with it. Cheers
Adam, thank you so much for testing this out.
I´ve modded mine also today but i was a little bit scary to use it :-P
I also upgraded the bars with 2.5mm² coper wire....but the idea to conntect both psitve lugs to the same spost is just brilliant! THX to the gut with that idea!
Have a nice holiday
I purchased a unit in Dec 2020 and was about to do your mod but discovered they have fixed the problem by putting a diode in series with the 1000uF (big green cap on MOSFET board. This capacitor now feeds all the electronics including the MOSFET drivers. So power supply can dip to zero volts during pulse and MOSFET drive remans at 11.5V during the ON period.
I'd caution against directing people to Aliexpress, eBay, Amazon and any other similar websites when purchasing semiconductors. Unfortunately there's a major problem with dishonest sellers distributing fake/counterfeit parts. As a general rule, it's best to purchase from an authorized vendor whenever possible.
Kudos on the repair AND improvement. Having gotten a better look at the guts I may end up buying one of these for an upcoming project.
I think the battery still doesn't have enough amps in terms of instant output and is struggling.
300 A is quite a lot of electrons! It is a typical starting current for an engine and lasts several seconds. If anything the battery is way too large for the lask.
The paper that came with mine said 120 to 180 amps delivery range for lead
@@johnstonewall917 - the battery he is using us not a car starting battery. Also, I very much doubt that it is new.
Hello, this reaction might be a little late but how did you determine which mosfet it is? And what if i don't get a continuity reading but when i switch the probes i do? Regards
All's well that welds well.
Very punny!
😐
If the display has a current limiting resistor, maybe change it out to improve the visibility of the display? Or, use a trimmer pot?
Congratulations on fixing it. Well done! (now I know when ordering such a spot welder to include an order of extra mosfets at a decent price..)
Or just put the cap in before you use it
If you removed the faulty mosfet,would it work with the other 4 with the capicitor fitted ??
Great follow up. Thanks.
GR8 Fix & NO smoke;... way cool
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.
Maybe a capacitor would be easier...?
@@user-2uf2kr2c No... a higher capacity battery (automotive) would eliminate a lot of these problems.
Hi adem i spotweld a big 120 18650 lifepo4 tot gether and thanks for your inspiration
I ordered 10 to220 low rds mosfets from digikey mounted them on a copper bar and used the control to switch them
Great Video Adam... Just explain pls after modification.what types of Car battery should be used..? 12v 40Ah 300 CCA or More. Pls
Bigger the better really, but with the super caps I got away with an old 17ah AGM.
I've got exactly the same issue, down to the 1st attempt and identical scorch marks in my wooden bench. Mine came with 2 spare mosfet so I reckon I need to do this. My initial issue (I think), is also power supply related.
What's the best battery or power source and what are the parameters for a got power supply? Many thanks. 👍
I have one of these. Did the cap mod straight away. Also loaded up the tracks with more solder and shortened the cables as much as possible. Works fine on 0.15mm strip and a nice chunky car battery. Tried a 5000mAh 70C Lipo but it wasn't as consistent.
Ended up making my own spot welder using a rack of mosfets controlled by an Arduino and it'll weld up to 0.4mm strip. Will happily weld a 13S 14P pack of 18650s start to finish without even getting warm. Weld time adjustable from 1ms to 40ms.
Hi TGYAMatt. I would love to see your design on TH-cam or somewhere else.
Sounds like the way to go.
Thanks.
@@jamesgordon8960 hi James. Sorry don't have a YT channel. Happy to send some pics but not sure the best way.
@@TYGAMatt Hi TYGAMatt. Sorry I don't know the best way either. It's not a good idea to make email addresses public. I guess I just need a bank of very low on-resistance high current MOSFETS an Arduino timer adjustable from 1ms to 40ms with a buffer to drive the gates. I can't think of any other smarts that should be included in the circuit. You may be able to suggest some.
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@@jamesgordon8960 yes, I used ten mosfets in parallel driven by a TC4420 mosfet driver.
A couple of big ass rectifier diodes to stop and naughty spikes after firing and also a couple of TVS diodes to clamp any excess voltage.
An ATtiny85 is the brain. Not much to the code to be honest. It just senses a connection from the positive probe through a voltage divider into a digital pin, and then does the firing. Its a twin pulse, so a very short 150us pulse, then delay followed by the welding pulse which is adjustable as I said from 1-40ms by twiddling a potentiometer. Have a SSD1306 display just to show the pulse time. The code is all port manipulation to ensure the fastest speed.
To be honest, the actual hardware just follows what I found online on various forums with a couple of tweaks. The code is mine but nothing to it really.
@@TYGAMatt I use to think every youtube user automatically have a channel
FYI the new version of this spot welder which I just received has this problem fixed: they moved the FET pilot circuitry on the main board and used the onboard 1000uF cap to limit the Voltage drops so the fix is no longer necessary!
I just bought one that had the new version and the middle MOS tube burned out on my 3rd attempt at 30E pwr. I was using a LiPo 5000mAH, 3s, 90 C-discharge, w/ a XT90 batt connector. For the life of me I can't figure where I went wrong and why it fried so quickly. Any thoughts, would be greatly appreciated.
@@ttttenney was it this one: th-cam.com/video/VQR9cTcP5Bo/w-d-xo.html
They implemented a fast gate switch off mod also, I checked with my scope using a limited current PSU to see if the gate voltage would drop but it didn't so that problem is definitely fixed. I did a few welds using a small 12V 20Ah AGM battery (45Ah is suggested but I have a CCA battery tester and that one gave well over 240Ah) and all went well. I suggest you clamp the 2 positive wires on the *same* positive lead to avoid any further losses (no need to go through the PCB track for that) and be sure you have good contacts. Having said this, when a FET fails usually it is the one that either has less GATE voltage or has most internal resistance (least efficient). If you remove the blown/shorted FET the welder will still work though with limited current handling but should still be able to test weld. The reason they are using many FETs in parallel is not because of FET current handling reasons but for internal resistance reasons (the more in parallel the less internal resistance but the more prone they are to be unbalanced as they ought to be all matched perfectly which is near impossibile plus their capacitance is increased which is why you would need a proper FET driver). Just be sure you batteries are well charged and can deliver the CCAs (at least 100Amps) and that your connections are solid. Of course it could very well be that you were unlucky enough to have a mismatched FET!
@@Luca_Techy your detailed response and link were more than I was expecting, so thank you. Yes, mine was the exact one shown in the link, which is even more surprising as to why the MOS tube burned so quickly. I'm an RC guy with lot's of mAh / cell variations of LiPo's on hand, and I understand the importance of good solder joints and contacts. The LiPo I used was newer and fully charged, so again that's why I'm so confused. Like you suggested, I also de-soldered the the burned out MOS tube and tried again, but it just didn't have enough umph for my .15 Nickel strips, even at full 99E. I've got another one on the way and will do what you've suggested by connecting both + wires to the same terminal. Like you, I also have a 12v 55Ah AGM, which I use for my trolling motor and will give it a try with the new one. Thanks again.
@@ttttenney There are also other issues to fix such as adding an inrush resistor in series with the cap diode. Check out my latest videos on the matter before using it!
@@ttttenney i had the same problem.
Been a while since I have seen an electronics video from you!
I did the 1000uf capacitor upgrade and beefed up the trace with solder. I've been spot welding 0.2 nickel plated strips on 35 setting
I am a pretty green with.ic's and what not. although I have learned NEVER skimp on flux. weather installing or removing. I can see you have oxidation,flux will fix that and also help transfer heat better! I am just getting to figure these hings out more and more! .Hope it helps. though this is 3 years old? OI also use a normal brilo pad , along with tip tiner. keeping the tip covered at all times is key to not needing to 86 your tip and loose interest in soldering all together like I have in he past!t only thing is cheap store bought brilo oxidase fast, they are dime a dozen though!~ if I ever get round to it I will get a nice cleaning kit...
Resistance spot welding. Dont press the electrodes so hard.
Yes that is right 👍👍👍
I did the same plus I add some diodes for reverse current protection.
Mine came from BG in Dec 2020 with a spare MOSFET, would you believe.
i had a similar issue and had to add more solder to the the pcb board to help to carrey volts as the pcb board fails to carry the volts more volts and has help or can add a bit of thick copper wire
Hi i did this repair but it make weak spot welds even on 80ah battery and power on 99 max.. do you have any idea of what to do
Hi you showed that with your blown mosfet, it had blown closed which showed as continuity, how would you check for one that has blown open please? Many thanks for your Help Guys!!!!
You disconnect the power and find the GATE (single pin), Cut the track or unsolder and lift it, leaving the Drain and Source soldered.
Now you must discharge the gate - short circuit the gate connections to ground (negative).
Use multimeter to measure the resistance between Drain and Source - should be open circuit.
Next, touch the gate with your finger which will slightly charge it. Check resistance from Drain to Source and it should be a very low resistance... that means Mosfet is working, re-connect the gate.
Thanks for the heads up. Your shortened explanation is a bit confusing, though, because:
If I understood Fabio correctly, the problem actually does lie in the control circuit. In the control circuit not having enough power to keep the MOSFETs' gates open. That's why the fix is done on the controller's side.
Do you know what thickness of nickel you were using? I am considering buying this welder and getting some .15 nickel to fix up power tool batteries... tho I may splurge a little more and order the malectrics spot welder I just wish I could find one of those available in the US
0.15mm according to the listing.
What was the battery that caused it to fail?
great stuff men im going to try mine now again because the first time i try the pulse was to strung .
Great video!!! Can you zoom in when working on board for closeup, just a suggestion
Sorry - that’s very difficult because the camera ends up stopping me complete the task. I’ll try again next time around. Thanks.
just wondering: wouldnt the weld be better if you put pin-thingy1 on the lower strip and pin-thinghy 2 on the top strip?
Didn't you watch and listen to the video before typing that?
And please tell us how you can put one probe INSIDE the battery that you are welding.
Mine just blew up, but for a different reason. The one I have is a newer revision (bastards etched off all the part numbers!), on mine the entirety of the gate drive circuitry and controller are powered by a massive 10000uF capacitor fed via a series diode. The gate drive is sent through a 100 ohm resistor to what I think is an NPN transistor wired up as just a basic inverter (common emitter). That feeds what looks like a standard totem pole arrangement of BJTs and a bank of 30 ohm resistors that drive the gates.
Mine blew up after a few weld attempts, too. Mine does not have the diode on the secondary logic board but instead a small LDO in it's place. I verified with a scope the voltage does not sag (with a current limited supply and the output shorted) so this mod was unnecessary. However I think I figured out why it blew up: the 30 ohm gate drive resistors are absolutely tiny, I think they were 0603 or even 0402 parts. they were all way too high resistance and under a microscope I could clearly see they were blown! I replaced them with larger 0805 20 ohm resistors from digikey. Really I think 1206 would be in order for these ones. Would have also preferred to see a proper gate drive IC rather than a dodgy implementation with generic discrete transistors.
Unfortunately I think now something is wrong with the controller, it does not appear to send pulses to the gate drive circuit and does not seem to register presses. Also I'm curious why they chose to invert the signal to the gate drive, as when the controller boots up the output is enabled until the MCU is up and running which seems like a design flaw, it certainly caught me off guard.
Top tip, through away the module and just use the leads to manually use it. Only got mine yesterday and didn't manage to do anything but blow holes in everything and explode an 2016coin battery (with flames). Thought i was maybe not giving it enough current as display was dimming, then accidentally joined two motorcycle batteries in series rather than parallel and blew the fets. After abandoning it i have already welded a couple packs together with no prior experience of battery tab welding. Hold one leads contact down firmly and tap as quick as you can with the second leads contact, then I reverse leads and repeat. Quickly learned that if there is any air gap between the nickel strip and lead contact it will blow a hole in the nickel.
Hi, i have the new revised model and this one also burns mosfets, apparently you need to change a resistor this time, i did that and it keeps burning mosfets. Looks like it keeps the current open for too long.
Using too weak of a battery could cause the voltage too drop during the short few milliseconds of the welding process to the point where the gates on the MOSFETS to be only partly open and not close properly. This will cause the MOSFETS to blow.
@@sd906238 thanks, aware of that always using fully charged batteries. Issue still happens. Is yours the same exact type and it's trouble free?
Is there anywhere I can buy this welder in the USA without going to Aliexpress.
It's almost impossible to buy anything on their site
Needing help with mine. I put the capacitor on for the mod and now it only chirps when turned on and doesn’t do anything
hey Adam, do you know where to get "thick" 0,3mm x 8mm wide nickel strips? I prefer pure nickel its for high current application. Right now I just use 0.12mm strips, that is fine but I have to tripple it up, my welder can do it - its a Kwelder so. To save time.
I buy cheap stuff from Ali and I expect if I sanded it and put it in water it would rust... sorry
3h ago I got mine from Amazon UK (August 2021) and the board looks identical as on the video and it does not have the cap. Haven't tried it yet as I am still waiting for the nickel plates.
Good fix. Wonder if it would work by just using a power supply (like a 12V 5a one) and the super capacitors. Happy holidays and stay safe!
Possibly. I don’t think the super capacitors are particularly potent to be honest, but I figured they could only help in this situation.
You could hook up a power supply to run the MCU separately to the battery so it didn’t suffer the voltage drop. I don’t know if a power supply would suffice, I’m going to do my best not to blow it up when it arrives so I probably won’t be experimenting.
You'd need an absolutely MASSIVE power supply, something that would cost a lot more than this shitty little welder. There are far better ways to make these if you are willing to invest $$ rather than the cheapest possible solution.
When you're faced with that much solder to de-solder you'll need a hot air gun. With a temperature set to some 270 Celsius, just hover around the failed mosfet until the surrounding solder starts to melt, while your other hand holding a pair of SMT tweezers ready to lift it off the board. Once done, clean around the area a bit, place the new mosfet and heat up the surrounding solder again until it melts, add some flux to it to help the solder adhere and smoothen and the component will sit itself on its pad. Voila!
does a 16v 1000uf capacitor work as well?
Some times it helps to add resistance by changing the alloy of your tips. cheers
Have not seen a schematic for one of these but have a question about the FET's. How does one get an FET to work with only 2 circuit connections? I see that the components have multiple terminals yet there are only 2 buss connections on the PCB. At least it appears that way from the video.
If you look closely the lone gate pins are visible on one side.
You could also add some bare copper wire to the board to beef up the current handling capacity.
Thanks that leaves me with some hope
Hello Adam, how are your 3.7v lithium battery doing, any update on those? seems like you don't come around often?
Does your fixed welder always read 12V across the welding tips even when not welding? I made the cap modification, when I try to use the device regardless of manual or auto setting it does a small spark when touching metal and resets (powers off then on again.)
Nice solution
Can i use a 12v 60amp SMPS. As the retailer suggested that i can use this spot weldet with 12v 40 amp SMPS. Should i use an smps? I have made the capacitor mod as per fabio specs. Please help me. Thank you
Got mine a few days ago and used one of those car battery jump starters that I bought from costco uk. The specs were starting current 200A and a peak current of 400A. I was hoping this would work but I ended up blowing the large capacitor. What battery do you recommend using with this?
You could use your battery, but not connect it backwards (which is what blew the capacitor).
Take a proper battery, 3s 5000mAh LiPo 50c or a 12V 40Ah lead acid car battery and you are happy without doing any mod´s of the spot welder. This thing is working fine without any problems only by using a proper battery. Also you can weld 0.2mm nickel strip at 25-30E setting.
This is simple request but I’d like to see one prob on battery then second probe on strip. I’m thinking current should flow thru the strips from top to bottom not sideways. Just a thought. Mines coming Wednesday I’m gonna try both ways. I used to spot weld sheet metal and current had to pass from top (positive) thru to bottom ( negative).
I bought this spot welder. Will it work with a 4s lipo at storage charge 15.3v? I was thinking about running a few of them in parallel. They are rated at 75c
yes.
What happens if we replace capacitor with low/ high capacitance capacitor?
Thanks for the upload, enjoyed the fix process. Will it work without the capacitor bank or was that put in for protection or smoothing?
It was added because my ageing (and fairly small) lead acid battery may not be able to deliver the current or needs to. I’m yet to try it without the super capacitor to be honest. I probably should but I don’t want it to break again!
@@AdamWelchUK cool thanks.
@@AdamWelchUK Looking at the battery you have, looks like an SLA battery of about 17 or 18ah used in UPS units typically. New they can discharge about 230amps but they also have a low cycle life so you're probably well under that now. If you have a second one I'd double it up or maybe pickup a lawn tractor battery, they are usually about 30-35ah and can discharge 300 amps pretty easily and are pretty cheap in the states, about $30 not sure where you are at. I just ordered one of those welders but I'm going to use it with some lifepo4 headway cells that can discharge 200 amps continuous since I have them already. I'll add the extra cap for like you did for safe measure to it.
What is the fets # the cheaper ones🤣 to replace mine what went in smoke ? All same ? Mine is last by the cap
Really cool one - Thank you sir!!!
I have a 5000 mah 3S 60P lipo I just picked up and this spot welder. It makes the noises in auto mode but nothing ever actually happens. Both the welder and battery are new. It says use up to .12 strips but at the moment I have .15 and am wondering if that's the issue.
Mine was a slightly updated version. After hearing everyone say you need a good battery I pulled the battery from my truck. First spot weld at 05 was very weak, so I changed it to 10 for the next one. This made a very good weld, but on the second weld it blew a mossfet. I followed someone else's advice and removed the blown mossfet. Next attempt was set to 10, first weld was perfect, next weld blew another 2 mossfets. Even with a good battery its still a crap product.
Did you add a capacitor? I have been using mine for 2 years now with no issues.
I removed burned mosfet, have 4 Mosfet in it, now I use two lipo batteries (3S 5000mah 35c) in parallel, and it welds at 5E perfectly, after 60-80 continuous welds - it slightly gets warm.
Hi Adam impressive I'm looking at getting one
Why do all mini spot welders come broken to Europe? I have already received the third broken mini spot welder from Aliexpress.
very good video, thanks for sharing
Adam Welch - destroying spot welders so we don't need to... :)
Being a HVAC sheet metal mechanic (tin knocker) many years ago I used a rather large bench top spot welder, pushing down on the lever it "pinched" the two sheets of metal thus compressing the point of contact giving it a good mechanical "bond" and switching the transformer on and creating a good strong weld. This is what you have to do to have a better spot weld by pushing down a little harder on the probes, it appears that you're just touching the point of intended weld - not good enough. And lets face it, most of the problems you're having is the lack of current, just go out and purchase a small car battery.