At last, someone who reads the notes and watches the Vids, so many reviewers using the wrong batteries, not just back up batteries, thanks for an objective review...

You'll be fine going over mah. What matters is the discharge rate (50c on the lipo / CCA on the car battery). If the battery can't discharge quick enough, the voltage will sag and the mosfets won't fully turn on (saturate) which can cause them to heat up and let the magic smoke out. Mosfets have a spec called RDSon which is a curve of resistance as it relates to gate voltage. When the battery can't discharge quick enough, voltage drops so the mosfet gate voltage drops, and resistance through the mosfet goes up. Resistance = heat = smoke. Good video by the way and good explanation for people aren't familiar with electronics

This tutorial is dare I say it, spot on.

I spent a couple of days researching this little piece of kit before I buy one. This is by far the best and most informative review I've found. You confirmed my own thoughts and I'm now happy to buy one of these. Well done and thank you - keep up the good work.

Awesome video. I'm using a 45Ah AGM deep cycle battery and setting 30E, using .15T nickel strip, on 18650 cells. Works great. And this is coming from someone who uses a $10k dual-pulse battery spot welder professionally. I absolutely recommend this little thing to DIYers and enthusiasts.

I have a cheap unit similar, my first few welds (tab to tab) were useless but like you showed us, I was holding vertically and pressing hard. Getting much better welds now, thank you.

I watch this video twice. Once before buying the welder and now after I bought it, just need some practical info on how to use it properly.Thanks for sharing !

Your advice worked on my welder which I just received (Feb 2022). I tried it with a 30A radio power supply (didn’t work) before buying a 200 CCA riding mower battery which works fine. Still, I had to re-learn what you said about not pushing too hard on the leads. Every instinct is to crush them down and that just doesn’t work. Just short of firm gives a bit of spark and a useful weld. Fortunately the circuit is robust enough to support a learning curve. Very helpful video!

OMG, you're my friggin hero! So, I bought these little battery powered spot welders off Amazon, and was super excited to test them out. They have decent reviews, so I was expecting them to work. They're similar to what you've got there, but different in the fact that they have their own internal battery/power supply. I have tested them over and over, medium strength, max strength, thinner nickel, still I couldn't get a proper weld to save my life. Even when the strip stuck, I could easily peel them off, no good at all. I was getting pretty sad, about to just give up and send them back to Amazon, but I decided to do some more research first... In watching your video, you just hit the nail right on the head for me! I was pushing really hard, and even harder when it wasn't working. I was trying my best to get the probes straight up and down as well, thinking that a nice firm, solid contact would be best... Jesus, was I wrong!! I decided to try your advice, pushing less hard, using the corners of the probes, just being gentle with it... For the first test, I also turned the power down to a medium range. Holy sh*t, what do you know, after trying and failing dozens of times, I just got an AMAZING weld for the first time!!!! I can't yank this strip off at all, it's on there gooood!!! 😊😊 I am so happy man, thank you so much for the informative video!!

I just now got my little welder in the mail. You have just saved me from blowing it up. Thank you.

Thanks. I'm going to upgrade to welding my zinc strips. no more soldering.

Based on your review I ordered one. Experimented with various AH batteries and found the higher the AH the lower the weld # required. Stared with a 18AH AGM motorcycle battery, good welds at a setting of 60 I settled with an 80AH deep cycle battery. Perfect welds at a setting of 10. Great little unit, especially considering the price. Thank you for your efforts.

Thank you for your great instruction. After watching you video at least three times, I just finished using the spot welder to assemble 15 Sub-C batteries to rebuild a Dewalt 18-volt battery pack. Everything worked just as you described.

Thank you. The best informational video on this spot welder so far! I'm excited for mine to get delivered.

Much appreciate the clear product overview along with the very informative best-use insights.

Great video I was putting too much pressure with the leads on the strip and did not get a good weld. Thanks

Sir. You clearly understand this very well, I keep trying to explain to people about C rating or just the amount of amps a battery can safely dump... many are not really clear about that.

yea nailed it. there is a vid on adding a capacitor to protect the mosfet from low voltage and that is a good thing to do. i use a 2200 80c lipo.

A good easy to understand review, well done. What I gleaned from other videos about this welder was that being made in China, it does depend on luck a little bit in terms of quality. The mods other videos talk about are to address that uncertainty in quality. The typical problems are too thin and uneven PCB traces making the MOSFETS not truly parallel, but putting an unfair proportion of the current through one or two of them. Also lack of voltage maintaining capacitor over the control circuit is a serious design oversight. It is that absence of the capacitor that requires powerful batteries to operate this welder reliably. A smaller battery drops its voltage during the welding pulse. That results in the drop of voltage on the gates of the MOSFETS bringing them out of saturation regime into linear one and blowing them as a result, as no MOSFET can survive the currents involved when in the linear regime. By inserting the capacitor (Fabio's fix) the voltage on the control circuit and correspondingly on gates of the MOSFETS is maintaned high during the welding pulse, so you can safely use a smaller battery. Aslo reinforcing and evening out the PCB traces improves reliability and hopefully reducing the heating up this video poster reported.

Appreciate you taking time to make this video, all of my questions we're answered in this video. Gave you a thumb up and subscribed to the channel. Keep doing what you do best and enjoy the day.

Outstanding illustration of inducing resistance (localized hot spot) by not jabbing the probes into the nickel strip and battery! Thanks for the video.

Spot on, yes you are correct. The battery voltage drop causes the mosfets to blow up. I have seen modifications that would help but the key as pointed out is a battery that can delivers enough amps to do the weld with minimal voltage drop.

Thank you bro. Well explained. I have purchased a simpler version than what you used but have not yet used it . You have potentially saved me a headache of blowing mine upon first use. Thank you - a great video.

100% correct of the operation and requirements for the mini battery spot welder. Excellent explanation!

Sir you have gave me the best advice ever thank you so much I was pushing down way to hard on my maletronics(best spot welder ever imo)probes, welds looked crappy and burnt looking and I had to dial that sucker to 60ms to get the welds to stick which I now no was ridiculously to high.But since I have been applying less pressure man what a difference my welds look clean and almost machine like now and I'm only using 15ms of power now and have to use pliers to get that sucker off now.I'm glad I stumbled upon your video because god knows how long I would have been welding the wrong way,so thanks again for this amazing and in depth video.

Thank you Sir... Excellent, down to the barest of bare explanation of what's needed to make this product work like it was designed to do

Thanks for the electrode 'pressure' tips, and all the other explanation. Really useful.

Thanks, now i see why i randomly having bad welding, i was focus more on tip distance , but pressing too much.

Wow, what a great video. And reading the manual...I love it!

That's incredible, there's so many amps you see the wires repel each other as the current flows.

Love the fact the welder will auto weld, no trigger needed. I DiY mosfet welder last year with car battery. Works great, but I use foot switch. Had this been available would of bought this. Would like to compare with one I built.

Thanks for clarifying issue about that stay safe.

Lots of practices even as a hobby mig welder for few years but hard to weld until I heard that "just barely touching it to keep that strip". Many thanks mate.

Thanks for the video! It’s truly amazing the amount of current a LiPo can put out. If you were planning a busy day you could run a small balance charger i the LiPo. Have a great day and be safe out there!

What you need is a battery that has a maximum current (rated in A) equal or larger than the current requirement of the welder. Because the welder pulses are so short, the battery capacity (rated in Ah) only matters for how long you can use the battery before recharging. As you explained, these two battery parameters are related by the discharge rate (The number before the C). There is absolutely no problem in using a battery with higher discharge current than the specified in the welder manual. The welder should never be operated with a battery with insufficient discharge current capability, but on the other hand, using a weaker battery should not result in blowing the Mosfets. If that happens, that's an indication of a poor design.

Thank you for explaining everything so well, now I'm going to try one of these welder!!

as a engineer of 30 years DUDE you nailed it ! most fools should watch and learn from you

Thanks for this very informative intro to spot welding. Freakin' sweet little gadget too.

Thanks for the review

In other words, he is saying that the source battery is sagging in voltage under load, and that puts the MOSFETS in the device into their linear region rather than saturated, and the heat dissipation kills them. Can be hack /solved.

What a great video man!! I thought i knew what i was talking about spot welding but now i realize i really didn't understand everything. Thanks so much for the information and for the heads up about that sweet little spot welder!! I'm ordering that bad boy next payday. Great vid !! Aaron

Great tip on not pressing too hard ! ( Too much pressure = too low resistance = no heat = no weld)

appreciate your explanation. best video on battery tab spot welding.

Awesome tips. I definitely would've just pushed too hard and not got a good weld. I've definitely seen videos of people doing similar things on youtube. Some reviews even say they burned a hole without getting a good weld and this explains it perfectly.

Like the video, I think your analogy between voltage and pressure, current and water flow are spot on. The problem could be the design of the circuit and a weak battery being the single source for all power. Car batteries are designed for this type of work, consistent voltage at high current loads. I wonder how many welds you can perform before you must recharge your battery?

stunning video tutorial !!! Thank you so much for the video !!!

Wow man! Great video! You obviously just started your channel not to long ago ( I’m guessing). Great audio, great voice, great at explaining shit. I’d recommend you crank out as many videos ASAP. I could see people really liking you. Much appreciated and once again, 👏. Looking forward to seeing your channel take off.

Great video, thanks for making it!

One of the best videos on a tech issue I have seen. Thanks!

Thankyou much. I was going to spend close to 200. On what I thought I needed in a battery spot welder. Going to save big.

Its all connected to the internal resistance of the battery. High battery IR=big voltage drop within the battery itself which means the voltage across the load (spot welder) drops very low during the weld process.

Your assessment is correct. Technique is key, and there is a certain “bandwidth” the welder needs to be within to operate correctly (produce good welds) and not burning up MOSFETs/damaging battery cells. I’ve seen a schematic of this handy tool. There is no built-in current limiting in the welding circuit current loop. Once triggered by the control circuitry the MOSFETs close the remaining “open” in the current loop between the battery terminals and the welding probes (assuming the probes are making contact on the nickel strip). Assuming ideal MOSFETs and battery, the “high” resistances in the loop are the contact landing sites between each probe tip and nickel strip. Resistance causes heat with the passage of current (in this case it’s a heat spike) in each of the landing sites. That’s what we want as long as it is NOT TOO LITTLE OR TOO MUCH battery supply current. Hence, the published battery operating current range given in the instructions! If the current capacity of the battery source is within bounds: 1) Damage to the device won’t occur by pressing too lightly with the probes but the resistance will be too high and yield high visual sparks. Welds will also be inadequate. 2) Damage may occur to the device by pressing too firmly because making a circuit path with high pressure contacts reduces resistance of the contact points. This means inadequate heat is generated/no heat spike at the contact landing sites, no (or maybe very little) melting/welding AND you may damage a MOSFET or two if the higher allowed current (of your chosen battery) is beyond the limit of the MOSFET(s). I don’t know for certain but it may be the upper limit given in the instructions is what will save them in the event probe contact resistance is too low. This is why you won’t want a battery with higher op current as it may provide too easy an opportunity at too hot a heat spike or blowing a hole in your battery can (neither of which anybody wants!!!). If you have a battery with too high current capacity: See final statement above! If you have a battery with too low current capacity: Lack of adequate current will cause voltage droop. A droop in voltage is likely to cause a malfunction in the MOSFET control circuitry, the severity of which will cause improper control of the MOSTETs and one of them (or more) will likely blow. I’ve seen this lead to no more welding capability (MOSFETs blown “open”) to permanent current path closure (MOSFETs burned “closed”). This is extremely dangerous as the current path will not cut off until one of the welding probes is broken away from its landing site. By this time the nickel strip will be glowing orange or yellow and battery cell likely damaged if it didn’t already initiate signs of self destruction. Attempting another weld will immediately result in another burn. Disconnect the welder from the battery source. If one dares to return and test the welder again it should be done touching the probes to a 12V automotive lamp with tungsten filament. If it turns on immediately at least one MOSFET is burned closed.

Nice job explaining everything! I still put the mods into my version 1 red welder. Maybe not needed in my case, but sure works well,

You are an awesome instructor!! Thank you! This is the most informative and practical video on these little spot welders, so far. I was backing off from giving it a go.. until I saw your common sense observations. Thanks again!!

This by far is the best video I have seen explaining on how to use this device. Thanks and God Bless you.

Awesome, and great video! Regarding battery current supply: are there capacitors in the welder? Also, the battery clamps used have *good* clamping force.

I have always found that if I want and need something to work I can find a way to make it work. But for 25 bucks if I had to blow one up to get past tge learning curve id say it would be worth it. I spent 250 on my welder and its bad ass but I'm also going to pick up tge cheapo for the money thanks to your video it will be nice to have a spare laying around

thank you bro, i was gona send it back till i see the technique. whats the best deal on 18650's?

you are perfectly correct regarding the battery usage on this mini spot welder on other youtubers. who are using small batteries .

Nice info. Thanks. What about using a server power supply with big capacitor in parallel?

Thank you brother! I have a different unit, and was frustrated that my new scooter battery didn't seem to have the umph. Your breakdown was very useful to help me understand. While it's enough to crank a scooter, the 6ah isn't enough potential for the welder to do its job. Unfortunately, my directions were 100% Chinese, but you came to the rescue!

Best how to use it video that I have found so far. Thanks for the great work.

I just ordered one and I have welded before both arc and mig, I have a long background in soldering and most of my electives in college were electrical engineering classes. That being said I hooked mine up to a less than optimal Optima I have hooked up to 2 solar panels on my shed. This spot welder did nothing but beep and twitch from 10 - 85 increasing in increments of 10 up to 70 and then to 85. I finally put it at 99 and it popped pretty loud burned a decent spot on my 2x4 but didn't weld the 2 strips. Now the leads are constantly hot and whatever microcontroller is no longer working. I may order another one after I get my refund for this one just in case. I'm really wanting this to work as well as yours does.

I agree with your theories here. Never had a use for this unit but what you have shown looks to be correct.

Like the analogy!!! Makes perfect sense!

Very good information. Do you have a link to that exact welder?

Thanks dude good job im going to buy one of them welders now .

Thank you, saved me. I really appreciate your effort to help me!

Spot on... Don't forget to also do the Capacitor and Positive Terminal Mods. Those mods will put even more reliability on your side. Great Info on the weld probes contact pressure...

Nice explanation. Really appreciate the demo on contact pressure. I understand now why the other video I watched had the unit fail. As mentioned by others, the battery voltage drops if not enough capacity or wiring resistance not low enough. The FET's will not have enough voltage to keep them on hard. That could be solved with a separate source for the FET control but understand for the price, using a good source works. Not sure if anyone noticed but if you watch the wires going to the battery, especially on the higher power setting, they move slightly during the pulse. There is high current and resultant magnetic field moving those wires just in case there are doubters about the current capacity needed. The small LiIon battery worked because it has much lower internal impedance and higher current capacity as you stated. With a lead acid battery, it needs to be much larger to provide that high current. Thanks for the video!

Seems like a task specific welder? What else would it be good for, especially needing such thin metal? Thanks!

I like to add a few more comments, although the practical aspects were already made very clear. My belief is that thew Energy setting is plain time. Higher number = longer time for the applied current (heat). The current is determined by the total loop resistance, which includes the battery internal resistance, the MOSFET resistances, the cable resistances and finally the contact resistance at the weld location. Now, a little of basic math. The current is = Battery voltage divided by the mentioned loop resistance. The same current is applied through the entire loop. And then the "secret" -- the heat at any location within the loop is the Current Squared times local resistance. So, this says, if the local resistance is Zero, no heat is generated at that place. Remember the demonstration with high probe pressures --> no weld! All the heat was generated in the cables, the MOSFETs and inside the battery. The destruction of the MOSFETs is likely to be caused by DROP of the Gate Drive, if the the battery voltage drops. That is where the Cranking Amperes come to play. Basically they tell what the battery internal resistance is. Bigger batteries tend to have lower resistances and higher cranking amperes, but the ampere-hour number is only a rough guidance. The cranking amperes is the most relevant figure. And one final point -- the gate drive for the MOSFETs is taken from the same voltage that remains for the control box after drops in the battery internal voltage as well as the input cables. If the weld location resistance is very low, with near zero drop there, more of the drop happens inside the battery and in general before the point where the gate drive voltage is picked. The typical MOSFETs operate best with 14 to 18 volt gate drive. The 12+ volts is OK, but under the cranking conditions the battery voltage and thereby the gate drive is likely to drop below 10 V or maybe even below 8 V. At that reduced gate drive the MOSFET resistance is much higher. And more of the desired heat for the welding is instead heating the MOSFETs, which blow up sooner rather than later!

I set up my welder similar to yours except for I used automotive battery clamps and I did the Cap mod on it. I used a regular car battery rated at 800 CCA. Built a battery pack about 60 welds set at around 10 on the screen. No problem once I got the hang of how much pressure to use with the leads. Just to be on the safe side I let it cool for 5 minutes after 10 welds.

I am glad that you pointed out the problem that some other reviews have created. Spot welding is an incredibly current demanding application, and those 7.5ah lead acid batteries used for backup batteries and trail cameras just won't produce the number of "angry pixies" that are needed to run a device requiring 100 amps. The lawnmower battery is the best bang for the buck for about $20-25, where the car battery is more than capable of providing that current but at a much hight cost, say around $100. You can use bigger capacity batteries with no ill effects, so don't worry about using the larger car battery, or even a truck battery for what thats worth. It is only a concern if they are higher voltage or less current (Amperes) than demanded by the device. Some devices provide for overvoltage protection, others have undercurrent protection (to keep motors, etc. from being damaged), and others provide for both overvoltage and undercurrent protection. With spot welding, low voltage and high current are the name of the game, and that means big fat conductors from the battery all the way to the leads. Now here's where this enginerd is thankful that those other people ONLY had the $20 device let out the magic smoke: IF the MOSFETS did not get burned up and cut off the flow of current but instead failed in the closed position, the people could have had the battery they were using possibly "explode" like short circuiting a car battery or they could of had the battery they were welding tabs onto sink all that heat and then "explode" by getting them too hot for too long. Oh, I have a thought on how those backup batteries could be used with this welder (which is really just a programmable timer from 10 to 90 milliseconds), which is to have several of them wired in parallel (+ to +, - to -) so each battery only has to provide a part of the current required. Dependind on the size it could be six all the way up to 12 (possibly more if really small backup batteries are used). A capacitor bank could also be used. But I digress because either of these options is much more expensive than getting a $20 battery from Walrus-smart and just getting on with the welding. You got a new sub here. Well done.

Thank-you for postng.I've been leery of these welders because of the high failure rates in the reviews. I'm like you,only interested at the hobby,tinker level,not building a solar power system.Guess I'll pull the trigger.Thanks again.

A well-reasoned and practical review. Subbed.

Make sense. One of the reason MOSFET prematurely burn out is not the drain current, but insufficient gate-source voltage. MOSFET needs to be turn on hard, provided that gate voltage doesn't exceed specified limit. I suspect low-power battery will have significant system voltage drop hence not enough gate voltage, that cause MOSFET to burn out.

great video and info....so many people fried this thing by using moped battery than they complain cheap thing didn't work.

best video on UKposts with this welder THANK YOU! :D

3 mins into the video. And now I'm a subscriber.

I am an Electrical Engineer and had problems initially because the seller sent me the unit with NO instructions. Your explanation is very good, especially the recommendation of using a slightly lower pressure on the probes when welding. Before going to the internet (UTUBE), I blew up and removed two of the FETS that were shorted out. I solved my problem with using two separate power supplies, one for the weld (8V) and another for the control circuit (12-14V). Other solutions on the internet are good as well. Adding the 1000uF capacitor to the control circuit AFTER the onboard diode is another good solution. I am using 3 series 3000uF supercapacitors as the welding supply (8V) using the positive probe straight from the "welding" supercapacitor supply. The 8V supply was not sufficient when powering both the control circuit and the welding circuit. The FETS need at least 7V at their gates in order to provide their low resistance for proper welding. I do not have to worry about any voltage drops through the PC board. The negative onboard probe connection works fine and my board has only 3 FETS still switching after removing the two shorted devices. The lighter pressure you suggest allows a better heat buildup under the probes just as you described with your analogy of the mechanical switching/arcing points under light pressure. The bad FETS on a damaged board can be identified by measuring the resistance from each of the gate input (pin 1 on the FET source side) to the source (or drain) and identifying the ones with lower than 10 Ohms resistance. Remove the bad ones with a lot of solder and replace if desired but the board will still work fine with 3 FETS if you are careful with the "welding" supply. I have ordered some FETS from AliExpress and will be offering them on Ebay shortly for those interested in replacing some or all of them. Very good explanation on your video!

Brother you're great. Simple and efficient info in how to get the right results. Thank you.

I love your video and your plain simple explanation. It really works, thank you.

Could you post some purchase inks for the welder and the cables you recommend/use?

Thanks for this vid dispelling all those myths about this unit. Very helpful.

This is perfect for a few dozen battery. Thanks

Thanks for this. I figured that all the people giving bad reviews don't know how to properly hook things up, especially not trying to put that much current through hobby alligator leads or however they had their setup. Great how you kept it simple and on point! How often do you recharge that car battery if you don't mind me asking?

Thanks, that's a really useful video, I just ordered one of these then hour on loads of the doomster videos! I have about eighty stainless steel iButton canisters to weld solder tabs to, as I am rebuilding some temperate data loggers to have replaceable batteries.

Another name for "spot welding" is "resistance welding". Same thing that happens to a wrench when you span the terminals of your car battery with a socket or combination wrench, trying to loosen the terminal bolts/nuts. The very small contact of the round wrench edge with either the other post, pice of sheet metal on the frame or disconnected(dangling ground terminal cable). The contact surface area is extremely small, less than a mm^2, and that battery has as much as 400-650 amps of instant power. It takes a cable the size of your thumb to handle that many amps and not melt, even then it can only handle the current for 30 seconds befor the installation jacket melts. I work on the electrical power grid and you are right on the money. Press harder + better contact + less resistance = no weld. The other problem with those tiny batteries are that they heat up fast due to low specific thermal mass. Hot batteries have higher resistance, which means less amps leave the battery, which causes lower voltages, those add more heat to the system, cooking the mos fets. Voltage is your like your RPMS, amps is your torque. Amps x volts = watts, 746 watts = 1 hp, rpms x torque = hp. (Electrical resistance) or Ohms = mechanical loss or (vibration/friction/heat)

I was wondering if it would be ok to use 5 2.6v super capacitors in series powered by a power supply with the welding machine.

excellent explanation, I was skeptical based on the reviews, but your video definitely sold me.

Thank you very much for the excellent information you explained it perfectly for me, really appreciate it!👍

Thank you! You saved me so much money and trouble

I hooked one of those (not exactly the same but similar) up to one of my 100AH LiFePO4 batteries (2C) and blasted the traces on the PCB of the welder apart. I'd been trying to get it to work, starting with a small Li-ion pack and it wouldn't make a weld even on the highest setting, tried a 12v lead acid car battery with poor results as well. So I hooked up to the LiFePO4 battery but forgot to lower the settings on the spot welder. The first weld blasted the nickle strip I was using (a .15mm thick strip) nearly in half and melted the traces of the welder's PCB apart, around the contact pad for the +out. The unit still powers up and I can adjust settings and everything but it won't recognize contact being made in automatic mode and with no +out it can't weld anyway. I think I'm going to try to solder the traces back together. If that doesn't work, I'll probably build one of the microwave transformer versions. All in all, those little spot welders are great for hobbyist use, as long as one doesn't get stupid using it.

with the low CCA batteries during the welding pulse the the battery voltage drops and the FET gate voltage drops so they are not driven to saturation so they over heat and blow up. Thats the real cause.

EXCELLENT Explanation!!

Thanks for sharing your knowledge. Excellent video.

45 degree angle for electrodes is best as you mention. Cold cranking amps implies the battery's internal impedance and does not directly relate to battery capacity in Ah. You are correct that the reason the MOSFETS blow is because the supply voltage sags and there is insufficient MOSFET gate drive to keep the MOSFETS fully "on". When that happens they dissipate a ton of power, get super hot, and blow. So you are right...using a wimpy battery with too high of an internal impedance will cause the supply voltage to sag and thus kaboom. My solution: 12V 7Ah battery in parallel with 0.5 farads of capacitance. Works fine! Most people don't have a 0.5 farad capacitor laying around unless you have one of those kick butt stereos in your car. Nice video!

Thanks for the explanation. Clear as a bell.

Thank you for that great video