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- เผยแพร่เมื่อ 23 พ.ย. 2024
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Testing and explaining the cheap mini battery spot welder. If used incorrectly it will cause damage.
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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...
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.
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!!
your post put a smile on my face thank you very much sir😁
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.
Thank you, you will enjoy this little spot welder 👍
there are several versions, depending on what version you got, there are different issues needing care and mods.
Same here. Ordered it halfway through the vid after my thoughts were reaffirmed. Its the truth for most stuff you buy. Use it right and it works. Try to cut corners or use it improperly and itll be crap. Same issue people have woth fluxcore migs. It wont work if you dont use it right lol.
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
Thank you for comment and the clarification. I keep several tubes of magic smoke on the shelf, it's just a pain to get back in the component sometimes 😁
@@tetradgroup Weird... I do the same (putting it back into component) thing too 😳 Except, instead of tubes of magic smoke, it's jars of my fart
So sorry I'm very new to all of this stuff just fiddling with mine. I just had a little go with it to see if it worked with a 12 volt 12ah battery is this considered dangerous or stupid or both 🤣
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.
a BHVR might help (Big Hairy Voltage Regulator)
@@johnswoodgadgets9819
Really, a half Farad capacitor as mentioned by one commenter is all that's needed.
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.
This tutorial is dare I say it, spot on.
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I somehow lost my login password. I would love any help you can offer me!
@Nova Silas Instablaster :)
@Manuel Justice I really appreciate your reply. I found the site thru google and Im trying it out now.
Takes quite some time so I will reply here later with my results.
@Manuel Justice it worked and I now got access to my account again. Im so happy:D
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@Nova Silas You are welcome :)
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!
Thank you so much for the reply. Do you have a video explaining your mods by chance? I would definitely order some fets just to have on stand by.
@@tetradgroup I don't do videos but tried to make it clear that the board design could have been improved significantly by just add the capacitor that other videos have described. I did not investigate the board to find out that they had already used a diode to isolate or protect the circuit; if I had, I would have also just added the capacitor. I did not desire to use a large and heavy battery since I already have the supercapacitors to supply the welding current. I have also ordered a stack of 6 500F (2.7V x 6=16.2V max) capacitors to see if this would be a lightweight solution to the heavy battery problem. I would also add the capacitor with these smaller supercapacitors. The probes being delivered with these units also seem to vary from video to video. My probes have an offset machined smaller diameter tip; some use what appears to be a crimped copper pipe with a small tip.
@@tetradgroup
Here’s a video of the mod:
th-cam.com/video/fdnO0Z-scjA/w-d-xo.html
I just now got my little welder in the mail. You have just saved me from blowing it up. Thank you.
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.
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.
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!
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.
Is it possible to provide a link to the above referenced video?
@@Animatronicbear th-cam.com/video/6j-FcRLQrYs/w-d-xo.htmlsi=I19h5f866orUa6oh (Diy Mini Spot welder capacitor mode)
100% correct of the operation and requirements for the mini battery spot welder. Excellent explanation!
I bought one worked fine full battery set welded perfectly, two months later went to use again same set up but blew the mosfets instantly.
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.
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.
Same here! This is a very common mistake for people.
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!
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.
The problem with the design is no low-voltage protection for the mosfets. But, if you ALWAYS use the welder within the guidelines, you won't need the protection. As you said, having a battery with a current capacity greater than recommended is no problem. In fact it's good, as batteries deteriorate with age and the and no longer make the advertised specs. There's a video out there that shows the fix for the problem by adding a 1000ufd capacitor in the circuit.
Thanks. Two questions. Can i use 18650 battery in 3s Xp? how many parallels do i need for 30A discharge rate.. and.. can i use a transformer? how many watts do i need in 12v output? thanks in advance
th-cam.com/video/6j-FcRLQrYs/w-d-xo.htmlsi=I19h5f866orUa6oh (Diy Mini Spot welder capacitor mode)
you are perfectly correct regarding the battery usage on this mini spot welder on other youtubers. who are using small batteries .
I bought a brand new lawnmower battery 250 CCA and it's not working at all..
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!
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.
Just needs more gate capacitance
Great video I have found the fets get too hot, and i have to limit myself to 10-15 welds then rest to allow to cool for a few min. Afraid I will melt the solder around the fets . Then I have to repair or wait 2 -3 months to get a new one from china. Also try SPIM08HP batteries from battery hookup in 3s cheep and easy .
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.
The difference between this and a mig or tig welder is that the operator can select the current for mig and tig; but these cheapos rely upon the "touch" because all you can change is the time the current flows. That's the setting everyone is talking about adjusting. >>>NO real Current control at all
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!!
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.
Thanks for this explanation. There seems to be a lot of debate wether or not a 12vdc battery with extreamly high current can damage the mosfets. I plan on testing that theroy with some extra units I purchased.
@@tetradgroup I agree and look forward to your outcome! My hope is the current will prove to be appropriately limited by the welding site itself using adequate welding probe pressure/technique no matter the quantity being made available in excess. If true, providing higher available current will just be unnecessary overkill, no need to buy a bigger source battery. Still, if someone wasn’t careful and applied excessive pressure at the probe/contact landing sites, that overkill current could be destructive to the battery cell. This last remark is akin to using a sledge on a nail where a hammer would be plenty. The sledge would certainly drive in the nail but at what collateral cost to the surroundings! Thank you for studying this, sorry I tend to write too much.
Looks like you got the second version of it what the problem is is the controller chip dying keeping the feds open circuit well dying by adding a capacitor and circuit with the controller chip make sure it doesn't die well the spot weld is in progress protecting the feds
Awesome explaining the batteries
Thanks for sharing
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.
Thanks for the clear explanation, you are spot on, just go get a lawn mower battery and happy welding. So many people try to over complicate this. Sounds like your a fellow aVe fan 👍
@@tetradgroup Yes Sir! One of the first 50k subsribers to his channel if I remember correctly. And just to let you know, after commenting I watched a 'capacitor fix' for these units and I have to say it looks like way more effort than just getting the garden tractor battery and using the leads provided, or using the same wire gauge or larger (smaller ga. number) to add short extensions as you did. That's the best options for a bench unit, and I think in the rare circumstances where you need to take the welder to the batteries instead of the other way around that lithium pack you have will be fine. The only reason that I wouldn't suggest using it all the time is because of their finite life measured in charge cycles combined with the higher cost of the pack.
If you were using it full time out in the field and could justify the expense for the most compact form I would say get three of the 5000mah lithium cells (I have some that are the 2650 size cells, so 26mm diameter vs 18mm diameter for the 18650) tab them in series (3s1p) then shrink wrap them. Velcro them to the unit and done. If you went 3s2p you could more than double the expected life of the pack and cut the peak stress in half (which would lessen the butt-clench factor for me), but that's assuming they make it to end of life without being unintentionally 'decommissioned' by any of a million things that can (and do) go wrong when a tool is out in the field.
Best wishes
I bought one of these in September. Blew it up, I guess. What you are saying about low voltage makes sense. I ran across the capacitor repair video first, and then this vid, but I think you are saying the same thing. One problem I had was I thought I had a 35 aH battery. It was a bit old and it tested as 10 AH. I got a second welder. I don't understand having a battery that is too big. The current should be a function of the circuit, but maybe this circuit is messed up. Seems like they are close and would have a decent welder with a bit more work. Nice to see people working together for DIY. Big thumbs up!! You have some beautiful weld and I appreciate the tips on how to make contact. Little things like that could make people give up.
George, he's talking about current not voltage, in regards to needing high/more current.
A weld is almost like a direct short. The only things that limit the current passing through the weld is the internal battery resistance, and the resistance in the metal of the weld. But the MOSFETs have a maximum current rating. If too much current is pulled through them during a weld, they will burn up. A big battery that can deliver too much current is bad.
If the battery is too small, then the large current draw will cause the battery voltage to drop. If the voltage on the mosfet's gate is below its saturation voltage, the mosfet goes into a region where it has more internal resistance to current flow. This is called the linear region where current is proportional to gate voltage. If too much current passes from drain to source, the internal resistance will heat up the mosfet and cause it to fail.
Thus the battery should not be too small or too large. The li-ion batteries with the high current rating will have very little voltage sag and will not cause the problem of too little gate voltage. However choosing a battery of any chemistry that can supply too much current can blow up the mosfets. This is because the circuit does not limit the current.
There are videos that describe adding a capacitor to supply voltage so the gate voltage doesn't fall below the saturation threshold. That seems like a good idea.
Here is a video that explains the linear and saturation modes of mosfets: th-cam.com/video/5eG6CvcEHJ8/w-d-xo.html.
@@eideticgoone7035 -- if the MOSFETs were passing their max, you would be right, current would be limited by batt int. resistance and weld; but they aren't. Here, MOSFET current is determined by the adjustable gate voltage NOT how much current the input can deliver. So battery being 'too big' cannot ever be a problem with this device until you had the power level set to maximum by which time you'd have welds burning and lots of other problems.
@@a.lexiconn9387 I'm currious how you know that the MOSFET's are operated in their linear region by adjusting the voltage. I would have thought that the power levels would have adjusted the duration of the pulses. i.e. their timing, not the voltage on the gate. But I don't really know. The auto mode already is turning on and off the welding so it just seemed likely that it was working in the MOSFET's current saturated region by timing the pulses.
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.
Great tip on not pressing too hard ! ( Too much pressure = too low resistance = no heat = no weld)
That's incredible, there's so many amps you see the wires repel each other as the current flows.
Outstanding illustration of inducing resistance (localized hot spot) by not jabbing the probes into the nickel strip and battery! Thanks for the video.
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.
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.
This by far is the best video I have seen explaining on how to use this device. Thanks and God Bless you.
You are correct. If the battery has a high enough internal resistance (undersized battery), during high discharge, the battery voltage will drop below the threshold required to keep the FETs out of the linear region (between off and on). When this happens, the FETs are conducting but the voltage across them is significantly higher than the ideal 0V.
Thanks, now i see why i randomly having bad welding, i was focus more on tip distance , but pressing too much.
Thanks. I'm going to upgrade to welding my zinc strips. no more soldering.
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.
I’m a automotive technician with a lot of electrical experience I know what ur saying about using the small batteries. There are so many electrical failures due to things like ur talking about. For instance take my vw golf diesel I work on a whole fleet of these for my buddies delivery business if you have to small of a battery the starter will spin too slowly taking longer to start making the solenoid get super hot and eventually ruining the solenoid, the battery will not last long. Many people that put an amp and subwoofers in their cars will blow up an amp and/or speakers complaining that the brand they bought sucks but then you look at their set up and it says on the amp the ohm limits for for how you have it set up and they have the speakers hooked up to where it’s half the ohms that the amp states it can handle which is like trying to drive 100mph in 1st gear and they don’t adjust the eq and gain levels so when it’s turned up the speakers are super distorted ruining them. This is something huge that even many auto technicians don’t even know I’ll give you an example of a time I dealt with this before so I have a car come in with a misfire I check it out it needs a ignition coil, ignition module and spark plugs, the manager comes out with the customer saying he had all of this stuff replaced at 3 different shops and did it himself last time and he just replaced the spark plugs this morning so it’s got to be something else. So I tell the manager to go get a factory spark plug and come back. I get my multi meter out and I measure the ohms on the factory plug and then the Bosch triple platinum plugs the customer used so the customer could see the crazy difference in ohms and I explained to him when the ohms are that different it’s like trying to drive 100mph in first gear the coil and ignition module are designed for the factory spark plugs resistance (ohm’s). Think of resistance as a funnel the less resistance the bigger hole in the funnel the higher the smaller the hole so when the aftermarket plugs have half the resistance the funnel drains much faster so the aftermarket plugs are letting the electricity fly through the coil and module over heating and melting the electrical parts inside. The customer said I don’t think you are right but if you guys are going to guarantee this will fix it then go ahead and do it. I said if I am given spark plugs, coil and module all factory acdelco it will fix the problem. I replaced the parts and he came back a few months later for an oil change said it’s been running great and he can’t believe the spark plugs were the problem and asked how I knew that, I said well I worked at the dealer and we would see this all the time and most regular shops don’t know stuff like this.
Oh and you can use as big of a battery as you want that will not be a problem at all. A battery doesn’t force current into a device the device pulls it out. Just think of it like the recommended battery is ur gas tank half full and a big battery is a full tank.
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.
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.
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)
Great video that gives justice and restore some value to a great product. Please stop apologizing to those engineers. They are well aware of their goofs. You've analysed and spotted the problem dead on: The gate voltage of the MOSFET must always be stable and high enough to decrease the resistance from the drain to source junction so that it drops as low as its specified by the "RDSon". This will allow the large current needed for the weld to not develop a significant voltage drop across that junction and heat it up to blow it off. MOSFET will allow current in excess of 200A without problem BUT only for a fraction of a second with a minimum cooling period in between surges. Oversizing the heatsink and smearing coumpound will decrease the time required for that cooling period to a couple of seconds. Adding large ouput stages capacitors will also help decreasing the required current capacity in Ah that is needed from the deep cycle backup battery although a LiPo battery would be by far a better solution in my opinion.
you have to understand that this device is just managing a short-circuit by usng a switch (the transistors).
The only parameters you can change here is the length (time) of the short circuit.
But once the circuit is closed (short-circuit) , there is no way to control the amount of current passing.
So if you have a battery with some oompf (over 200A) and the cables are thick (allowing the current to freely flow), you could exceed the rating of the transistors.
That is why the instructions suggest to use a battery with a capacity that will self limiting the inrush current.
On the other hand, using a too small battery can create another problem.
Since the small battery won't be able to provide enough current, you will naturally increase the time of the short-circuit.
Since the transistors are not totally transparent and still have a low resistance, increasing the time of short-circuit also increase the time allowed to the transistor to heat. After a few solder, you could reach a very hot temperature if you do not add a heatsink to the transistor or allow them to cool a bit.
another problem (that is fixed by modifying the circuit) is the transistor are like a mechanical switch.
They can be open or close, but also be in-between. when a switch is in/between, on a mechanical switch you get a big spark.
With a transistor you get the equivalent of a resistor. so if all the power of the battery is passed trough a resistor, the resistance gets hot. The pupose of a MOSFET like those is to go from infinite resistance (switch open) to almost no resistance (switch close) in almost no time, so almost no heat is generated. This is the SWITCHED MODE.
Another mode is LINEAR MODE (variable resistance).
If the transistor is not triggered enough, (low voltage on the trigger pin), it is just stuck in-between and a lot of heat is generated, enough to burn the transistor.
This cheap spotwelder is know to exhibit this problem (in both versions) and there are fixes for that.
The first version has a bad design, the diode and the capacitor are mounted the wrong way, so they have no effect.
(voltage drops in the circuit, then trigger voltage also drop and transistor goes in linear mode and overheat)
On the second version (capacitor and diode installed correctly) but have a resistor on the trigger that has a too big value (around 1k).
It must be replaced by a smaller value (0.50k), so the voltage that trigger the transistor is bigger and ensure the transistor change from the non conductive mode to the full conductive mode, instead being stuck in linear mode.
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!
I bought one of the spot welders that have a battery on them. Cost 16$ i think.
Works fine, i've rebuilt 2 complete ebike battery packs with it. No problem. Although it does have a tough time with thicker nickel strips.
Nice vid ;)
Do you have a link to your welder?
It is very simple to blow it up.
1) Plug it to a battery, then use the switch to turn it on
2) You can use it or not. Then turn it off by using the switch.
3) Unplug the input from battery and short (maybe by accident) the two plugs that were connected to the battery previously (but not now).
You will have a spark then your device will be down.
The only way to prevent spark and damaging, is to power on by the switch after disconnection until there is no current left.
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!
That's a known issue with many of these and there is a modification that can be done to prevent it. It involves adding a capacitor to the board to prevent the voltage to the driver from dipping too low. I did the mod to mine with great success. There are videos about it on TH-cam.
Nailed it mate. The difference between a low draw and high draw battery. CCA vs Ah is important.
Great video I was putting too much pressure with the leads on the strip and did not get a good weld. Thanks
It would seem you are right sir. Use a car battery and just have no issues. Thanks for the video. No more "take a chance soldering".
When your not pushing hard the current it focused on the small area of the weld. When you push hard the surface area of the plates is more which means less current per give area which mean no weld. Your technique makes complete sense.
I don't understand the probe pressure, but I'll take your word for it. That seems opposite to what I would guessed; probe separation distance would have been my guess.
This does not work like an arc welder. It is a miniature SPOT welder. The weld occurs when the probe sends current through the nickel strip into the battery cap, through the battery cap to the other point of contact and back into the other probe cable. Current flows from the negative probe through the load and back into the positive probe. The better contact, the higher the current AND better the weld. If the current is too high, it will melt holes in the nickel strips and maybe even burn holes in the battery, worse case. To low of current, the nickel strip will not stick to the battery because there is not enough heat.
Thanks for the directions on using this welder. You can really over due it with a car battery and pushing on the tips. Works was better at 15 and a soft touch.
Thanks for the electrode 'pressure' tips, and all the other explanation. Really useful.
I agree with your theories here. Never had a use for this unit but what you have shown looks to be correct.
Say it simple cranking AMP is what you look for spot welding. So I highly recommend cranking AMP is the factor because this is a split sec AMP draw pull. So 2 things are major on those units. CONNECTION is the MAIN one. 10gauge wire with solid connection is best for those devices. On the display do not use over 50 because the board can't handle it and blows up the mosfets. And get yourself a manual switch and apply it to your foot so you can put the leads in place and with the food pedal you can trigger the weld. Works like a charm, because if you do automatic it can be a problem if you don't have very steady hands and the plate is slipping around.
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
Fire hydrant and garden hose. Yup. Kind of like a AAA battery versus a D cell. They both put out 1.2 volts but the D cell will do it for much longer without dropping below a half volt. Some of those guys with failures were probably doing an assembly line worth of battery packs. At eight welds per cell and 3, 4, 5 or more cells per battery pack and several battery packs to do, it wouldn't take long for a small battery pack power supply to wear down (sag down in voltage) and not turn off those MOSFETs. Pretty soon - mystery smoke. I'd still like to do the recommended modifications suggested in another video. Every design can be improved upon and made better. That's why everything has revisions. As a product gets used the weaknesses that were overlooked during the design phase become apparent.
Your 100% right. I boy burned up to saws using a 50' extension cord. The cord would not carry the current to run the saws right. Not enough current will make it fail.
The short answer is that with an insufficient battery, the high current discharge causes the battery voltage to drop below the operating voltage required by the control circuit. That causes the MOSFET to go to a higher resistance on state. Heat is generated and MOSFET fries. Using a separate supply for the control circuit would prevent that. However, this unit has no provision for that.
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'm about to do the same, I figured it can be backup to my car/truck battery lol.
@@JMGeranimo It's still working and have built several battery packs for my drills. One thing I do is not to work it to hard. After a few welds I let it cool before doing more. I think if you were to use it a lot without cooling it probably will damage it.
what’s the cap mod
cranking amps is basically that that spot welder needs, so they need 120-180 amps to spot weld, so a lead acid that can provide that amount of cca isn't going to blow up the spot welder.
This is great information, and likely the power source is a big part of peoples' problems. Just one small detail - A battery's Amp-hour rating doesn't demonstrate how much continuous current the battery can provide. The internal design of the battery cells themselves determines this. For instance, some LG 18650 cells are designed to deliver 30 Amps continuous, while most other 18650 cells are designed only to provide 430 mA or 1A continuous. As it happens, the higher-current LG 30-Amp cells actually have a significantly lower milli-Amp-hour rating, at 1,500 mAH, while the 1 Amp LG cells are available in 2,200 mAH up to 3,800 mAH. To achieve the required 150-Amps for this machine, one would need to stack many many standard 18650 cells in parallel, or be sure to use the special, high-current rating ones, also stacked in parallel, like the ones in the 50C pack you show. The Amp-hour rating refers ONLY to how long the battery will maintain its rated voltage when supplying its rated current... that is, it's storage capacity. If we're using the fluid analogy, the Amp-hour rating is, "The size of the tank." So, for the spot welder, this means a battery with a larger Ah rating will simply last longer before needing to be recharged, like how a tank with a larger volume capacity will be able to feed a hose of the same size at the same pressure for longer before running out of water, when compared to a smaller tank. Amp-hour rating has no bearing on the strength of a single pulse, unless it has a very, very tiny tank. The internal battery design itself will determine that - the size of the internal conductors, etc. - and a battery that can't effectively deliver a 150A pulse (which standard 18650 cells cannot, unless you stack many many in parallel, or use those special high-current rated ones) will suffer a voltage drop when the welder attempts to deliver the high-current pulse, which can cause the loss of the machine's ability to maintain control circuit voltage during the pulse. If the voltage drops too low during the pulse, the control circuit may not be able to hold all the FETs open, which could end up feeding too much current through the FETs that do remain open, which could cause those open FETs to fail.
So, don't worry too much about the Amp-hour rating, but pay very close attention to the C-rating, or the continuous current rating. Even stacking 10 typical 18650 batteries in parallel in, say, a 4s10p configuration, would only deliver a 10-Amp continuous rating with a burst rating of 30-40 Amps. They'd need more along the lines of a 4s60p battery using standard 18650's, or use the special high-current / high-C rating ones.
Excellent video. Seems to me that for the average Joe, a good rule of thumb would be if the battery has enough grunt to start your car, it can run the spot welder. The battery in my truck has a spec of 800CA/650CCA, so it's plenty good. By the same token, I would think that the Li-ion jumper pack that I have in the truck would also be adequate if it will start my truck.
Man i've got 2 spotwelders and just now learned how to spotweld, i was using way to much force because it sounded logical. Thanks for the explanation
If I understood your water analogy, it's actually reversed. The welder is a large hose, and you want to fill a 10 L bucket in one second. If your source - the hydrant - has an output of 1 L/s, it will take 10 seconds to fill the bucket even if the hose can carry 10 L/s. That's what the capacitor in the mods do: it's like a second bucket that stores enough water from the hydrant to satisfy your need for a large amount of water in a second. It fills up in ten seconds and it empties in one second, because its output is large enough.
Amperes/hour just means how much water the hydrant can deliver before running dry. What is relevant here, assuming a constant pressure, is the diameter of the output valve: how much water the hydrant can deliver in the second you need it. The cranking amps are definitely the number we need, if it actually means "how much current the battery can deliver at the nominal voltage for 30s" - CA seem to me more a marketing mumblejumble than a real technical characteristic, but if it's a real number, a 400CA battery is a battery that can push out 12V at 400 Amperes, enough to drive a few of those welders simultaneously. Then it probably dies, but your car is up and running and the battery's work is done.
So, a big reservoir sure can give you a lot of water, but if its output is a soda straw, you'll have to wait a long time to fill your bucket. A bucket contains less water, but once it's full it can deliver it in an instant.
Hope it makes sense, I'd use a more technical jargon if English were my language :D
Oh, and dividing by 7.25 in your mind? Boss!
It's not just the battery size but that is part of it. These mini spot welders have a fatal design flaw where if the input voltage drops too far during the weld the microcontroller can crash or lockup and the MOSFETs will clamp on hard to make the weld but then the microcontroller doesn't have enough power to strongly signal the MOSFETs to turn off. So it's not that the MOSFETs turn on slow, they turn on fast and hard but the lack of power due to the voltage drop on the input doesn't allow the MOSFET to turn back off and so they keep conducting well beyond the 15-20ms needed for the weld and they overheat and burn up. I have been through 4 of these little welders before I realized what was happening when I looked at the trigger signals going to the Mosfets and the voltage at the microcontroller. One solution is to add a large 1000uF or larger capacitor to the control board after the diode to help filter the power during the weld. Another solution is to power the control board with a separate supply so that it stays on even if the supply voltage drops. If you make a lot of welds, it is also a good idea to add a heatsink to the MOSFETs to cool them down.
I was using a 4s 25Ah LiFePO4 pack and these little welders tend to fail after anywhere between 20 and 200 welds depending on that input voltage. This was not continuous but 4-8 welds and then the welder had a minute or 2 to cool down. If it started to get too hot I would stop and let the unit cool down. I burned one of them up because I beefed up the cabling to 6 gauge going to the unit and flowed more solder with copper bar onto the traces to try and decrease the voltage drop. This helped with the voltage drop at first but it didn't completely fix the issue and after about 6-8 welds the Mosfets blew as the battery voltage at the input terminals would still drop quite substantially during the weld and the decreased resistance meant even more current was flowing through the Mosfets. The voltage at the battery terminals would drop a little bit but nothing like the drop at the input terminals.
Good information, thanks for sharing you knowledge of this little spot welder 👍
I just told someone on another video, this same thing. I use my red one every day and it works great. The guy didn't even set it up he didn't even try one shot he's like, "oh it doesn't work." And it just made me think about all these comparison videos, and how wrong they could be. But thank you buddy I sub to your channel because someone like me out there that really likes this thing, because it works💯💯💯💯💯
You can go over the amp hour rating, and that's fine. Your wires won't pass enough current because they're not big enough anyway. You run o gauge wires to this thing, you may be pumping too much amperage. But the Red Top Optima I run, has no problem getting the job done.
As far as I understand, having a battery that can supply more amps is fine. The amps (current) is limited by the voltage of the battery and the resistance of the weld circuit. Also, the length of time of the weld will limit the heat.
hi,and wish you all the best for the futur i made my own spot welder months ago, and like a lot in the comments it would,nt weld. i,ve watched all the advice on youtube and tried them all but nothing worked. today i came across your advice and thought i,ll try this as well as the others, and i have to say putting my welder on an angle makes a perfect spot weld on my replacement batteries in my cordless battery packs. i would like to thank you for the information you gave.
Thanks for this vid dispelling all those myths about this unit. Very helpful.
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.
great video and info....so many people fried this thing by using moped battery than they complain cheap thing didn't work.
Thank you. Not only that everyone thinks you have to do the low voltage capacitor mod, which is cool but I don't think it's needed if you have the right battery and keep it charged. Im sure I've done over 1000 spot welds with not a single issue.
Best review of The Spot welder I've seen. I'm convinced I'm buying it.
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
I rarely comment on videos, however this one is worthy of a big thank you for an effective explanation, demonstration and review
Glad it was helpful!
as a engineer of 30 years DUDE you nailed it ! most fools should watch and learn from you
IOW, the small 12V batteries suffer Voltage sag under heavy load. Those batteries (when NEW) have an internal resistance of about 10-15mΩ. but this increases with age and use. It's not uncommon for them to have 40mΩ and still be considered "good". If we assume even the lowest level of 100A discharge, the voltage of the (brand new) battery will drop by 1.5V. Then you have to consider the contact resistance of the welder Input Power wires to the battery... which could easily be another 10mΩ, causing another 1V drop.
Car batteries typically have 1mΩ internal resistance... so with that same 100A current draw, you'll only lose 0.1 Volts.
RC lithium packs, can still have 5-10mΩ internal resistance... unless you get GOOD brand, and multiple "P" (parallel) cells.
This battery internal resistance reduces the MOSFET applied Vgs voltage, which is the voltage that turns the MOSFETs ON (called Gate Drive voltage). If a MOSFET is not COMPLETELY enhanced (turned ON), then it will act more like a resistor... which will VERY quickly heat up, and in extreme cases... explode due to the fast heat buildup. Many MOSFETs require up to 8-10 Volts to reach their absolute minimum ON voltage... called "full enhancement". If that 12V battery is not able to maintain NO LESS THAN 10+ Volts during the spot weld cycle, then the magic smoke gets released, and the unit stops working.
Example: 4N04R8 MOSFET is rated at 300 Amps, and has a Vgs threshold rating of 4V... but guess what? In every high energy test shown, they use 10V Vgs. In their Vds test (Volts across the MOSFET when switched ON), the part drops 2 Volts at only 200 Amps when 5V is applied to the Gate, but if the same part has 10V of Gate Drive voltage, it only drops about 0.6V at 1200 AMPS.
Could this spot welder device be designed to prevent this? ABSOLUTELY... it would only require buffering the Gate drive power with a sizeable capacitor that had enough energy storage to drive the Gates of the MOSFETs during the weld cycle.
If the small 12V battery had a set of ultra-capacitors across it, then there would be no problem.
BTW... Using a battery that has a rated CAPACITY of more Amp-hours is NOT a problem... the only problem is if the battery in incapable of supplying the required Voltage without the voltage drooping under load. The battery can not "push" Amps... you could have a 1000 Ah battery sitting there powering it, and it would NOT cause any problem... just like on a car... you can always use a larger Group size battery without a problem... just don't try to use a 12v 7Ah battery in your car.
I've also seen where self-proclaimed "experienced electronics" people replace the wires provided with the unit with LARGE GAUGE WIRE... because "they only used xx gauge wire, and that's not enough". Well, did they ever consider that the gauge of wires used is part of the OVERALL SYSTEM RESISTANCE that limits how much current can flow??? NOPE... so "let's just swap out the wires for 4 gauge and make it work better"... now the current limit is gone, and POOF!! (some people have just enough knowledge to be dangerous)
purchased one because of this video and followed all your specs and blew on first use!
Not enough juice in a voltage source causes the MOSFETs to blow, they won't switch fast enough and they overheat. There is a fix for it by adding a capacitor to the board......but too late for that now. I'm sure you've seen all the videos on it by now. For a couple bucks you can replace the fet(s), thats what I'd do just cuz I hate adding more shit to the landfill. Bummer it blew on you first time around.
The "range" is a suggested number, and you really do not want to go lower than the recommended low. You are correct on that point. A device like this wont consume more energy than it's asking for and just because the battery is higher rated than recommended doesn't mean it will deliver more energy than the device needs. No worries on that particular point. If "extra capacity" being delivered to a device were a real problem, light bulbs, toasters and refrigerators would be dying every time you plugged them in. Electricity just doesn't work that way to a resistive load.
Besides that, those little UPS batteries are rated at much lower output and the internal physical makeup of these types of batteries aren't even the same as a high current battery for use in motor start applications. Do a little reading about the differences in car batteries vrs deep cycle marine batteries, if you are really interested. Needless to say they are designed different for completely different applications: slow long discharge or fast high current draw. Anyhow... your observations are pretty spot on.
I would also like to mention a few simple aspects of MOSFETs in general. You are also correct in your assumptions of what happens to a battery when you are trying to draw to much current from it. How does the affect an FET though? First off, understand I am going to speak in generalities. Typical MOSFETs "turn on" fully at a certain voltage but they also turn on partially at lower than "whatever it's max voltage is." When a MOSFET is not turned on all the way it is considered to be in the linear range. As an example (this is not precise) lets say the full turn-on voltage is 10v and here it will deliver very close to a full 12v (or whatever voltage you are applying) and you will enjoy the ultra low resistance of the MOSFET, that being no excessive heat from a resistance that can be measured in milli ohms (like 0.004 or lower Ohms). Now apply 5v to that MOSFET and it only turns on partially (for simplicities sake) to like 6v or so, this is not correct because the scale of output voltage is not a nice straight linear line. Where is the excess 6v going? Well that right there is a resistive load so the missing 6v is going into heat.
Keep in mind, there is likely some small amount of circuitry that knocks down the 12v to the (whatever) voltage to turn on the MOSFET. Now imagine a huge voltage drop in the battery and what this does to the turn on voltage for the MOSFET. You get a shit load of wasted energy in heat from the MOSFET and I certainly didn't see any beefy heatsinks on those MOSFETs, you would probably want something rather large made out of aluminum to dissipate that kind of heat, likely hot enough to give you a nice burn, or temporarily erase a finger-print (we've all done this haven't we?). This "linear range" where the MOSFET isn't turned on all the way is what is destroying them because there is not enough heat dissipation. This is why other's devices were dying on the 4th weld, simple heat build up beyond specifications.
As a side note I went and looked at a fix from Maker Fabio just now and he has it mostly right. Adding the capacitor to the control chip (this turns on the MOSFETs) keeps the voltage up to an acceptable level so it doesn't drive the MOSFETs in the linear range. This is not a "complete fix" IMO though because MOSFETs are a bit more complicated than that and you want to maintain a certain level of voltage difference between the pin that turns on the MOSFET and the pin that is sending voltage thru it; this is not as destructive as a MOSFET being in the linear range but it will have an impact eventually. Without understanding all the specific "why for's" your solution is by far the best, use a battery that is well above the required current draw so the voltage never dips below any required thresholds. You will allow the device to last MUCH longer and have greater performance out of it.
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...
I'm familiar with "maker fabio"'s capacitor mod but not any "positive terminal mod". Can you give more information please?
@@321tryagain Yeah... Put both Red wires (Bat and Probe) on the same Screw Terminal to not use the Positive PCB Trace.
I got a 10$ one from China
And rebuilt 3 of my streamlight flashlight batteries
It took some time to figure it out but once i got it dialed in it’s easy
I love it
I used 2 different batteries 95amp
And 45amp
And the small battery worked better
They were blowing them up because the main diode was in the wrong place. Newer versions have the capacitor downstream from the diode so it actually holds up the gate voltage of the MOSFETs. The newer version has the diode next to the capacitor on the main board.
For that price I plan to order one and play with it. I have several of those 38120 Headway cells that can easily discharge 200amps, I think a 4s2p pack with those would run this guy with no problems, similar to the Lipo packs and in that config would only place 100amps on the cells. 4s3p if I want to give it plenty of headroom.
Just a thought, but to be extra safe you could attach 2 batteries in parallel. I think it would then draw 1/2 C from each.
That is true, but really any tractor or car battery should easily supply 100 amps. I would buy a tractor battery at Walmart for about $30 and a cheap trickle charger to top it off.
@@ianbutler1983 it's not the cranking amps it's the continuous discharge rate which normal lead acid batteries physically can't provide
@@dylan-nguyen Who said anything about cranking amps? "Normal" L/A batteries, such as in a car, can provide hundreds of amps. It is far from continuous, merely a pulse of a second or so. I have no idea what you're talking about. Providing large currents for short times is exactly what L/A batteries excel at. doing. Starting engines, for example.
@@ianbutler1983 that's the problem it doesn't have the continuous discharge rate which is why as the video mentions lots of ppl have problems
you only crank your car a few then it starts up and the alternator kicks in.
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.
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.
I also bought a welding pen, two probes hinged together, sounds like the supplied probes will be better, as the probes of the pen are both parallel just like you say doesn't work well!
I have bought it 3-4 years ago :)
Connected it to a 12V battery (3s LiPo, capable of 250A :) the same as the one you are showing :) ). First weld, some of the mosfets just smoked and didn't weld at all after that...
So yeah, it is, it is garbage... Back in the day 7 out of 10 that would review this spot welder would get the same result as me. And yes, those 10 people had appropriate power sources... 3 out of 10 would just get a working unit. 7 out of 10 wouldn't. I didn't buy another one, 20€ were enough waste for me...
Best how to use it video that I have found so far. Thanks for the great work.
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.
Exactly right.
By his calculation , it would be between 188 and 300 CCA but I bought a brand new lawnmower battery 250 CCA and it's not working
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?
This fix to these blowing is so simple, all they have to do is add a big capacitor which can keep the voltage up for the mosfets.
Much appreciate the clear product overview along with the very informative best-use insights.
Thanks, everything you said makes sense, especially it needing resistance to generate the heat to actually weld, otherwise it just passes current to efficiently. At least that's the way i understand it.
Low voltage kills MOSFETs
Batteries internal resistance drops supply voltage as current increases
These welders use a lot of amps so the wrong battery will drop supply voltage during use and blow MOSFET. The battery will show full 12 volts after as it wasn't discharged it just can't supply high current and high voltage at the same time.