TNP #14 - Teardown & Analysis of a Somewhat Dangerous LiPo-Based Mini Spot Welder

[@xDevscom_EE]

These things also useful to stress-test power components and high-power resistors. Also nice for PCB shorts troubleshooting, since any shorted component will be burned away promptly. Beware, eye protection is mandatory :D

[@Thesignalpath]

I like that idea. Now I have to find a short somewhere...

[@tmmtmm]

and hope it burns the component and not the PCB traces :)

[@xDevscom_EE]

@@tmmtmm Lowest resistance loading will win the firework award. :)

[@kevina.4036]

Good for testing the 1st mixer in your analyzer.

[@BruceNitroxpro]

Best idea was that of EYE PROTECTION.

[@KerryWongBlog]

I just tested a couple of smaller ones before, they were not as powerful and the maximum welding current was in the 300-400A range. If you measure the current waveform with higher resolution you will likely see one or two short pulses preceding the main pulse.

[@mmpiforall5913]

1 or 2 short pulses before the main pulse is called 'prewelds' this provides a current path for the main pulse, without it, the main pulse could eject molten metal as 'weld splatter' or even burns.

[@jj74qformerlyjailbreak3]

Now I know how to fix mine. Not the same brand. But same design. Yours actually has Low Resistance with that extra copper and solder. Mine will today then I’ll test it. It would weld before, but after about 10-15 welds. It needed charged again. Once battery drops below 4.10v it’s worthless unless you’re welding foil. Thanks for the upload. God Bless.

[@efdawahfan]

How did your mod turn out ??

[@jj74qformerlyjailbreak3]

The battery swole. But I took a much bigger cell from a Lifepos4 motorcycle battery and it seems to handle the welds longer. It was a little tricky cause the cell tabs are on opposite ends. I haven't finished the 555timer version yet. Work. 😂

[@lazerusmfh]

I bought one of these, its awesome! Built several 12s packs already and it works really well

[@poptartmcjelly7054]

Car batteries are also good sources of welding current. I made use of a new-ish car battery i had that had a shorted cell so it couldn't be used as a car battery anymore but worked wonderfully for my spot welder. I connected my electrodes with 6 sqmm wire to limit the current to about 900A. The only downside is that they're bulky and heavy but they also last forever.

[@Zodliness]

I don't know if you're aware, but you can use salt water to reduce the current, when welding with a car battery. See this video for one example: kzbin.info/www/bejne/sJzHpKRnjMl-b8k

[@2xKTfc]

Conversely, a (regular) welding machine also makes a good starter pack for pretty much all diesel equipment with weak batteries. Just gotta make sure you have the voltage and contacts right...

[@BH4x0r]

​@@2xKTfcand have to make sure it is a DC welder instead of AC

[@jimomertz]

So now I know why the USPS asks if you are shipping batteries when you hand them a package. 🔥

[@darkknight145]

They're assuming you tell the truth. I just bought one of these of eBay, the delivery docket said it was a Tobacco Grinder.

[@EpicHardware]

That was the shortest signal path video i watched until now

[@artursmihelsons415]

Thats why I always opening and verifying new noname devices before powering up, especially, after shipping..

[@McTroyd]

Thanks for making this video! I only just realized my Amazon cheapie spot welder is probably the only electronic tool I have that I haven't yet taken apart. No issue so far, but never hurts to look. 👍️

[@AntonioBdeJesus]

Thanks Mr. Shariar, very usefull video!

[@wolfiexii]

I now know of a new tool I need. Thanks mate!

[@ginbot86]

I have this exact same model and was pretty impressed with its welding performance. I'll definitely have to take it apart to do similar touchups and shortening those tabs like you did on your unit.

[@graealex]

Actually the performance is crap. The capacitor-based ones running on mains have an order of magnitude shorter pulses. And thanks to Ali, these aren't that expensive either ("HT-SW01" for example).

[@ginbot86]

@@graealex Good to know, I'll have to look into those. To be fair this was the first time I've spot-welded battery packs so I didn't have a frame of reference to compare against.

[@arekx]

@@graealex Google and aliexpress search fails to find any welders with HT-SW01 symbol. Is this symbol correct?

[@BruceNitroxpro]

@@arekx , Hmmmmmm

[@graealex]

@@arekx Yeah, I noticed. Actually needs HT-SW01A or HT-SW01B C D etc and then you'll find the spot welders with 60J to 240J energy.

[@earlbucklin8323]

thanks for the time

[@KeritechElectronics]

Kinda nice device, and pretty compact too. I could get one.

[@paulpaulzadeh6172]

😁very funny when you say " nothing fancy" ,there is CPU here, but you need three guy with PHD to design that little tiny CPU😂😂

[@lolvivo8783]

Nice video. I would have liked if you could have measured practical current during welding at various battery voltages too to set a benchmark for current requirements. As the battery discharges the max current it could deliver would drop. And so this might be unusable below a certain voltage.

[@JerryBiehler]

Can you take pliers and pull off the tab and see if nickel strip is left on the battery? The one that Kerry Wong tested did not do a very good job and just left a couple marks where it was welded.

[@power-max]

I went with a cheapie on ebay that was around $20 to $30, the unanimous red PCB ones. They have major design flaws that results in them exploding the MOSFETs after like 20 welds at higher power. For one thing, they usually use comically-large capacitor to maintain a high voltage to the gate of the MOSFETs, and also lack any protection for inductive kickback. All the energy that goes into the loop inductance of the leads will backfire into the MOSFETs. I think the only thing that saves them is their drain-source capacitance due to large junction size? If they made the design into a half bridge with another MOSFET that shorts the output following the pulse, or simply a big beefy diode, it would probably be a lot more robust.

[@tookitogo]

Did you mean “the ubiquitous red PCB ones”?

[@power-max]

@@tookitogo maybe lol

[@T3sl4]

Solder a TVS diode across the MOSFET(s), SMCJ5.0A for example, anode to source, cathode to drain. Clamps the inductive kick. The MOSFETs probably die of repetitive avalanche (causes progressive internal damage). Greatly slowing gate turn-off is also an option; this increases turn-off losses, but it need not be much energy in comparison to the bulk of the pulse. Also, the losses include the inductive kick energy, handling that with less need for TVS.

[@power-max]

@@T3sl4 I considered it. Just putting a big fat reverse-biased diode across the MOSFETs turns it into sort of a one-shot buck converter, which should clamp the output spike. A TVS would attempt to dissipate the energy rather than recycle it, not sure which one would be better. I ended up getting a Kweld instead, much nicer welder, if a bit pricey.

[@BruceNitroxpro]

@@tookitogo , Probably.

[@dtiydr]

Interesting, thanks for the info.

[@ChibiKeruchan]

5:02 you forgot to mention the thickness of that nickel strips. anyway that part on 2:59 dan easily be first with liquid electrical tapes no need to cut them off. I was wondering if we can mod it to just direct it to a power supply rather than getting the power on a battery.

[@IanScottJohnston]

Looks a great wee unit, i have been eyeing them up for a while but put off, in general, by cheap chinese Lipo/Lithium-Ion battery/charging circuits (already had a strimmer battery fire!). Hmmmm, might be a candidate for a motorcycle battery conversion!

[@Adam-gi1yl]

Nice work n video 👍

[@marcinp.8108]

Shahriar, is your cat ESD-safe?

[@IanScottJohnston]

At the very least we know it has a CAT rating so good for a few hundred volts anyways.

[@Thesignalpath]

Only when wet.

[@sdp8483]

I double checked mine and it seems to be a different model with the batteries bolted to the PCB so no issue like you have.

[@ericklein5097]

OLED screen?

[@rickoneill4343]

These are becoming popular in the iPhone repair industry as you need to transfer the battery mainboard to a new battery for full oem functionality. I find whenever a new tool is required to fight the right to repair it speeds up the creation and sales of devices like these.

[@seldompopup7442]

I think iphone and any other phone batteries are soldered to PCB. Only batteries with steel case need these welder.

[@rickoneill4343]

@@seldompopup7442 they are mostly all soldered. Usually you would just buy a new or referb battery and install it without welding by clipping it in. However in the case with Apple they embed a serial number and other data that may require the pcb be transfers to a new battery.

[@jfbeam]

@@seldompopup7442 Maybe on the current gens, but the 5/5S/5C I've worked on have tiny connectors.

[@jfbeam]

People have had need of "battery welders" for many years now. Building your own battery pack has been a common DIY thing for years. Started out with RC toys, then moved up to solar systems ("battery wall"), RV's, and even traction packs for cars.

[@Zodliness]

@The Signal Path - Trusting the electrical integrity of most Chinese manufactured lithium powered products... 🤨 Is like sleeping with a live hand grenade under your pillow for a sense of added personal protection. 🤣

[@Flamenawer]

In china is made the good and the bad, you get what you pay,.in any country

[@PapaMike23]

That burglar will never get me alive!!!

[@bansci]

Great video, thanks! I wonder what the precision of this measurement was? The clamp meter is very fancy, but even measuring with shunts is challenging at high currents.

[@christianloria329]

i am using the cheaper version bare version (no casing) using 3S-4000mah 60C Lipo 2 in parallel configuration, it has setting up 1 to 8 and no 4 is so much sufficient for spot welding 18650s

[@peterlekkerkerker4482]

I wonder if te postman realizes what's in these packages bouncing in the back of his truck.

[@xwatchid]

How many welds can be done in it's lifespan?

[@davidbarker3591]

I've got the newer version. Cleaner assembly, large LCD screen, 88 gears, 10000mha. Welded .20 thick nickel..no issues

[@ericklein5097]

pure nickel or nickel plated steel? Because I own both versions and the older one actually has a battery with lower IR than the newer one (0.54mΩ vs 0.67mΩ). I found it to be roughly at the same level as the old one except my pens heat up very quickly and I suspect they were assembled poorly. Both welders could never really do a real weld with 0.20mm pure nickel even 0.15mm nickel requires being the kind with the slits in the middle to get a proper nugget left on the cell terminal. The board on the newer unit is definitely much more refined and the way they attach the lipo is far superior. If you haven't taken yours apart I would carefully slide the board and battery out just to check to make sure your bolts are tight. Be super careful not to short anything if you need to tighten them.

[@losaminos59]

Did you just touch the lead probes while shortening it? I always thought my hands would fry if I do this

[@Aexorzist]

Very low voltage and lots of resistance of the skin vs. super low resistance of the copper probes. I still would be scared haha.

[@TheHuesSciTech]

^ As Axel said. TL;DR: Current and Voltage are two very different, orthogonal things (and Power is sorta another thing).

[@alexsuykov]

@@Aexorzist it's not about skin resistance, he was shorting copper to copper. The point of contact between the leads could potentially get very hot and he was holding it with his bare fingers.

[@jfbeam]

@@alexsuykov The point of contact is very small, and there's a large amount of mass to sink that heat. Unless your finger was right on the contact point, you won't even notice it.

[@Zodliness]

You won't feel anything through your bare hands at such low voltages, unless you decide to unwisely try it on your tongue. Even then the above unit (not all brands) only power up and fire the pulse, once the unit detects a direct short across it's probes. I personally do not trust the electrical integrity of anything manufactured in China.

[@ericklein5097]

I have one of these and my board recently died. Can't find any blown components. Any idea where I should start probing? I had opened mine prior to seeing this video and my first wtf moment was the size of the lipo tabs. The seller has been absolutely useless.

[@ericklein5097]

Follow up, I couldn't get a new board for this so I bought the "upgraded" unit with the OLED screen and the XT90 probe connector....yes it is a slightly smaller battery with two 5Ah cells in parallel vs two 5300mAh cells in parallel in the Seesii model shown here...but the Seesii battery pack gives me an AC IR of 0.540mΩ and the new one gives me 0.670mΩ. Trying to find a way to parallel the two packs together and hopefully it won't be too powerful for the new spot welder which does have a much better looking board. They got rid of the stupid slots the tabs go through and went with a large pad that the tabs are bolted down to with a hole through the tabs and the board pad. Seems like a much better connection (and obviously safer) so maybe the difference in pack IR is a wash after you take the connection on the SeeSii into consideration. I didn't care for the cable and electrodes on the SeeSii unit but the new unit pens heat up VERY fast. I have a feeling its related to how it is assembled but I haven't taken the pens apart because its my current only working welder. I finally got my LSUC caps in from Korea after they did a tour across the Pacific with stops in Mexico, Panama, up to NYC and then getting off the boat in Virginia. Jesus that was brutal to watch. I also bought a CNHL 5000mAh "120C" Lipo from their racing line since it was cheap and I want to try some of the PCB boards. Perhaps I'll end up finding a 1S Lithium spot welder circuit I like and I could turn my Lipo into 3 parallel cells and then combine the four 5/5.3Ah cells from the other welders with it....or create a second 3S lipo out of the best cells from the spot welders if I stick with 12V who knows. Going to take a little bit of money to put the parts together for my cap welder and honestly I now believe 2S isn't enough and I need to go 6S but most of the control boards I've seen are for 2S and 3S configurations so 3S2P might be the way to go?

[@karlbesser1696]

When welding with direct current, the electrodes will wear out unevenly.

[@Flamenawer]

I have the same one, but it is rebranded, mine says DX10. I tested it when I bough it, with the included strips, just worked fine. After six month without use, but battery in storing charge , it doesn't weld nevermore, no idea if due it lost some mosfet (is that possible and carry on working?) or the new pure nickel strips are too much good, but I bough 0.15 and 0.10, and it is no able to weld. I tested the battery and it has 9000mah so it looks ok. I cleaned the probes, and improved little bit the first pulse. So sad, they are cheap, but even that is quite a lot of money for me. Just made 1s4p packs and needed weld them with iron solder

[@efdawahfan]

I have the dx10 too ...have you been able to fix it??

[@bfx8185]

Did you take a part your welding "probes" ? :D

[@supernumex]

Any idea what kind of spot welder Dan Gelbart built? Building Prototypes Dan Gelbart part 5 of 18 Spot Welding

[@d.a.nordquest3082]

Or of an up-to-date control circuit for spot welder similar to his?

[@d.a.nordquest3082]

In Dan's new "Workshop Tour" video at 32:08, he refers to a "miniature spot welder" that "works exactly as the big one" you reference. The miniature one is made by Weltek. It looks like a WELTEK 410E PRECISION WELDING HEAD, with a separate Weltek solid state power supply.

[@supernumex]

@@d.a.nordquest3082 Good find, although, I'm not sure if "works exactly as the big one" means that the internals are the same architecture or just that the principles of spot welding are the same, just in a smaller package.

[@ecospider5]

Having those connections short to the case would have been really bad. Surprised they haven’t had issues in shipping.

[@TheHuesSciTech]

The case looks anodized, which creates a thin insulating layer. Which is obviously not a good thing to rely on, but would probably reduce the actual incidence of issues enormously.

[@dfgoui]

at 3:34 it looks like he touches them at the same time with his fingers, so my guess is they're insulated

[@TheHuesSciTech]

@@dfgoui It's only a few volts. He can touch both terminals at the same time perfectly safely. It the terminals were shorted out by contacting metal, the result would be a huge arc flash or battery explosion. If you can't understand that the previous two sentences can both be true at the same time, you need to learn about the difference between voltage and current. Also, I don't think Shariah would have made such a big deal out of the issue if "they're insulated"...

[@Thesignalpath]

They are not insulated. They only sit at 4.2V. But they can deliver 1000A.

[@francisconotengo3477]

best choice......2 super capacitors 3000F in parallel.....12v spot welder board connect to external power supply....positive directly to the positive side of the capacitor.....is good?

[@johncoops6897]

Nope. Super Caps would not give enough current. People have tried it, and it doesn't work.

[@Thesignalpath]

Why do you think this? In fact, the thing super capacitors are really good at is extremely small output resistance and therefor high current capability. This system would work only better with super capacitors.

[@phuang3]

Mine copy is powered by two 3000F super caps in series. Each one is rated 0.5m ohm ESR. It's very easy to reach 1000 amps. The welder consists of four 300A mosfets in parallel.

[@gacherumburu9958]

👍👍

[@PushyPawn]

I bet the duty cycle of this thing is tiny. Using it for commercial or industrial applications will result in its quick death. (possibly with fireworks)

[@GTechno13]

Does anyone know if, given portability is not an issue, if a contactor would work or is there too much bounce?

[@Stumper52]

Minimal pulse length might be a problem...

[@lukahierl9857]

And you have to use a big one so that the contact dont Weld themselves shut. I have tried it with a old 20A 3ph ABB contactor and a car battery, with all contact in parallel, it did work for a few times and then the contacts diddnt open up and it wrecked the cell I Was welding on and gut the cabels nice and hot before I could react. I would not reccomend unless you go with one rated for 40A or higher, and even then I would Still recommend being care full.

[@doooofus]

sorry for noob question - so that lipo pack looks like 4 or 5 cells, which i guess they wire in parallel since no need for high voltage and we just want to maximise current... but if i wanted to make my own one of these but with LTO cells for better safety, how many more than that would i likely need? i am aware both chemistries are much more capable of short burts of ultra high current output than other lithium based chems but no idea what specs to check to calculate this myself. any ballpark figure would be appreciated if anyone reading this knows

[@km5405]

im guessing best way would be to take one cell and estimate what its short circuit currrent pulse capability was , maybe using one of these spot welder control boards for that even. You put in 1 cell, test the short circuit current. Then another cell in parallel to see by how much it went up ... hopefully that will let you null out the internal resistance and calculate the ESR for short pulses per cell.

[@Mueller3D]

You need to find out the "C" rating of the batteries you get. Search for "battery C rating" for more info.

[@km5405]

@@Mueller3D jup, youd wanna get very high C rating batteries, the ones they put in those crazy RC packs that can do 200C or something silly.

[@johncoops6897]

You need to consult the data sheet of the specific battery cells that you intend to use. Note that they have lower voltage as well.

[@JigilJigil]

The build quality looks like if it doesn't kill you highly likely it won't last long.

[@thekaduu]

But it may make you stronger in the process :P

[@Flamenawer]

In my case lasted the first test, it was ok, but stored it 6moths and it wont weld nevermore, no even 0.1 strips (pure nickel)

[@jcims]

Folks in here that use these, does the portability add that much value? I think I'd rather just run something off of mains or a car battery than worry that the lipo is going to go nuclear on my workbench or in a toolbox.

[@madinatore]

I would wager that the LiPos are cheaper than a supercap setup that would require more than of the shelf components on the power management side.

[@cda32]

@@madinatore The problem is lithium batteries are not designed to repeatedly be short circuited so eventually they will short internally and catch fire.

[@johncoops6897]

@@cda32 - Those cells are more than capable of coping with that sort of current.

[@sarahjrandomnumbers]

Inputt current is the best current. 🤣

[@hightechstuff2]

Do you like butter?

[@Thesignalpath]

It is alright. Why do you ask?

[@ReinoGoo]

Lithium-Polonium? (LiPo). Should be Lithium-Phosphorus-Oxygen (LiPO).

[@Thesignalpath]

Ha!

[@thenickdude]

LiPo stands for Lithium Polymer

[@wahyutriwibowo1803]

New nuclear/radioisotope battery? Nice

[@tamaseduard5145]

🙏🙏🙏

[@neiliewheeliebin]

These spot welders are rubbish not only do they weld poorly but when the fets short it burns the crap out of whatever you are welding.

[@Broken_Yugo]

Seems like a standard feature with this ultra cheap stuff from China, solder balls and sketchy lead dress.