Repair Attempt - Super Cheap Spot Welder 

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.

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.

Thank you, will try same mod. Waiting for replacement mosfet to arrive. Mine also blew up shorted.

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.

Really enjoyed your video Adam, so clear and easy to follow,...look forwards to the next one, Cheers

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.

Thanks for the indepth explanation i purchased one from amazon with capitors aswell did your mods today well impressed with it. Cheers

Glad to see you decided to repair it and get it working great show of that fellow percy virance :-)

Great follow up. Thanks.

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!

Thanks Adam, I replaced all Mosfets with 300A 12V Mosfets, it works great on 5E

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. 😥

Spot on Adam, great follow up, although I am enjoying all the videos of people smoking them.

Really cool one - Thank you sir!!!

Well done on fixing the spot welder. I was hoping that you would work out a solution.

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!

great stuff men im going to try mine now again because the first time i try the pulse was to strung .

Mine had a couple extra FETs in the bag, I guess they knew I'd need them, ha-ha, happy holidays!!

Thanks that leaves me with some hope

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,I didn't expect a follow up so quick😀

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?

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!

very good video, thanks for sharing

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.

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..)

All's well that welds well.

I did the same plus I add some diodes for reverse current protection.

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.

If the display has a current limiting resistor, maybe change it out to improve the visibility of the display? Or, use a trimmer pot?

Nice solution

Some times it helps to add resistance by changing the alloy of your tips. cheers

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. 👍

Right on good job

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.

Hi Adam - I just found your excellent video. I was interested that you used a super capacitor, and I bought the same 20F one from Bangood, and am trying to use it as the only high current power supply with a 12V current limited feed. I have not been able to produce decent welds, and with a scope I found that the o/p of the supercap board drops from 13V to 4V during the pulse. So those 6 caps in series have far too much resistance to do much, and I would suspect that they have little effect on the o/p of your 12V accumulator. Did you do any other experiments with supercaps?

Been a while since I have seen an electronics video from you!

excellent Video, very informative, would it had been better just to order a new spot welder, seems like you'd get more spare parts for a cheaper price than the 5 mosfet's alone?

I ordered 10 to220 low rds mosfets from digikey mounted them on a copper bar and used the control to switch them

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

Sweet! Turned out to be an “Expensive” super cheap spot welder !

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 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

Nice work.

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.

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?

Mine came from BG in Dec 2020 with a spare MOSFET, would you believe.

You could also add some bare copper wire to the board to beef up the current handling capacity.

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

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?

GR8 Fix & NO smoke;... way cool

Resistance spot welding. Dont press the electrodes so hard.

Hi adem i spotweld a big 120 18650 lifepo4 tot gether and thanks for your inspiration

Hello Adam, how are your 3.7v lithium battery doing, any update on those? seems like you don't come around often?

Great video!!! Can you zoom in when working on board for closeup, just a suggestion

So I am assuming if the mod had been done in the 1st place before using the mosfet would not have blown? Great video now how do we scale this up to weld steel ? ;) I was just wondering if using tungsten Tig needles would be good... stupid me.. that needs the argon gas to stop it burning up in the air.

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)

Great Video Adam... Just explain pls after modification.what types of Car battery should be used..? 12v 40Ah 300 CCA or More. Pls

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.)

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?

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.

Great little spot welder as long as you use the correct battery

Just waiting on my second welder to arrive as the same happened to mine. Tried it connected to a car battery is this wise, also is it viable to remove the mosfets from the original welder and use them as spares. 👍

I may get one I saw a review of several of these and cheap spot welders and they sell one with a battery already that seemed like the best deal

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.

If you removed the faulty mosfet,would it work with the other 4 with the capicitor fitted ??

hi adam big fan i have a question about your epever dashboard , i am setting up my own for my epever UPower inverter charger . i am using ubuntu, python, influxdb, grafana and everything work fine except for the 32 bits register conversion, for example PVwatt is split in two 16 bit data high and low . i noticed that you did a bit of program to solve this issue , i hope you can share your solution . thank you adam

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

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!

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

I always try to fix a broken item before I throw it away because I know I can no longer hurt it😁

What leg of the capacitor have you fused to the diode? I used the long one on the diode and the short one on the board. Tnx. Nice video.

Thanks for the upload, enjoyed the fix process. Will it work without the capacitor bank or was that put in for protection or smoothing?

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 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.

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!

excellent!

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.

Excellent

Where did you buy that flux? Is it any good?

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.

Hello Adam. I had the same issue as you, one mosfet blown on 1st attempt. I have managed to remove the faulty mosfet, just waiting for replacements to arrive - £6 for 10 from aliexpress. Now the version of welder I have has a different control board to yours, I suspect an uprated board but it does not have the diode on like yours. There is a 10,000uF cap across the input before the supply goes through the connector pins to the control board but then the +ve goes to the switch and then directly to the SE8533 regulator. There is already a 470uF, 6.3V cap on the output of the regulator - would you suggest I connect an additional 1000uf from the output to -ve or break the circuit and insert a diode from the switch? Any help would be appreciated. Andy

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.

does a 16v 1000uf capacitor work as well?

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.

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.

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

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.

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

i was using a external power supply, working as well, but i'll give a try to Fabio's mod, seems way more reasonable

What foot switch are you using?

What is the fets # the cheaper ones🤣 to replace mine what went in smoke ? All same ? Mine is last by the cap

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

Hi Adam impressive I'm looking at getting one

I KNEW you wouldn't leave it alone!

You have given me hope. Maybe I can fix mine. Do you have a number for the mosfets?

just wondering: wouldnt the weld be better if you put pin-thingy1 on the lower strip and pin-thinghy 2 on the top strip?

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'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.