How Does a Spot Welder Work? Review, Teardown and Analysis of a BIFRC DH20 Battery Spot Welder

[@KerryWongBlog]

Please turn off "Stable Volume" in the video playback setting (the first menu item after clicking the gear icon) as for some reason, this new KZbin playback feature made the video much noisier than usual.

[@francopieruccinifaria9454]

It is possible that when this battery reaches the end of its useful life, I can replace it with another Li-po battery of better origin and with a higher rated voltage (perhaps some graphene 2S or 3S) and continue using the motherboard of this system solder outside the original case? Would that even make the system work more fluidly? Thank You.

[@repairman2be250]

The battery voltage on this device is nominal 3.7 Volt. So, the answer is no for 2S or 3S or more.

[@abzaman77]

Single lipo cell delivering over 400 amps! I wander where can I get those cells.

[@souza1515]

I would like to know, what is the minimum and safe voltage that I can use it, before having to recharge?

[@simontay4851]

If i had this, i would definitely add multiple super capacitors in parallel with bat+ and the GND side of the FETs to take some strain off the battery. The super caps can be recharged slowly from the battery via a resistor after each use.

[@milvolts1]

Thanks Kerry, my BIFRC is acting strange all of sudden. Worked fine for few welds. But know it's melting the nickle strip every time I try to spot weld. Even on a lower setting. Tried swapping the leads but no luck. Also tried contacting Ali-baba vendor and no more vendor. Bought this about year ago.

[@philippe5394]

Thank you Kerry for this very interesting analysis.

[@KerryWongBlog]

You are welcome!

[@gibranzawahra4224]

thanks a lot for all the info and tests, i have received my spot welder today, it was a docreate brand even though the product description and photos said BIFRC DH30, unfortunatly a mosfet burnt on first 5 welds on first gear, i was testing it on the nickel plated strips included in the product, now the output is always on even when the device is off, and it doesn't pulse the output it's just connected straight to the battery now, it might have been a fluke and others might have better luck but the soldering inside is quite shoddy there are solder blobs on one of the mosfets, the mosfets should've been able to handle the current since they're rated for 320A contunious and 1200A pulsed, but maybe they're fake which would explain the short life span. i don't know if i can recommend it seeing how fast it destroyed itself on the lowest power setting atleast for the docreate brand ones maybe the BIFRC brand ones have higher quality mosfets, the pcb was similar but with different mosfets and controller ic, the mosfets on mine were G011N04 instead of the 4N04R8 they have basically the same cont. and pulsed Amp rating but maybe much lower quality....

[@nelchan2421]

Can i solder the pedal switch for this device?

[@Beyefendi32]

hello, would this device be garbage when the battery life is over?

[@GabrielKozsar]

Once the internal battery is dead , I would desolder the battery and solder wire to it with XT connector and use it with external battery pack. I wonder if the XT connectors (60A) can withstand those amp pulses without burning the connector down .

[@E-BikingAdventures]

There is one that does exactly that. The Sequre spot welder.

[@ricksanchez3628]

The battery on mine has given up. I can't find any info about the battery other than it is 4.2v and 5300mah. Do you think I could replace with say 10 X 20A 18650 batteries? What is the max output of the lipo battery inside?

[@Beyefendi32]

5500 mah x 120c = 650a lion piller anlık Max 30 amper verebilir paralel bağlayıp 500a çıkarmak geregerekir

[@cheddarzao]

One of the best videos that I ever seen before. Congratulations. 👏 👏

[@cheddarzao]

+1 subscription

[@Zen2ncd]

Im gonna buy this thing, but can i modify the battery to 2 Li-Po 4700MaH 50C on this module? Cause i already calculated it and i got around 940A. Is it bad? Cause that spot welder said "Max 650A"

[@BiqBanq]

How many 18650 cells contain this pack? It seems like a lithium polymer pack. I didn't get it actually...

[@joshjordrayschannel]

Hi....can you help me...the battery indicator is full...but when i start to welding the machine turn off....what's the problem...? Thanks

[@Jean-Marc_38]

Soit la batterie est Hs, malgré l'indication pleine. Soit la carte électronique est en panne. Généralement les mosfet qui sont Hs ( en court circuit)

[@joshjordrayschannel]

@Jean-Marc_38 thank you

[@nadeemuk6194]

Hi if I remove battery and bring two cable outside to connect a car battery will be okay or not

[@repairman2be250]

No, not OK. This device is running on a nominal voltage of 3.7 Volt. Charged up is about 4.2 Volt.

[@jonamvro]

please i want two cable pen for Bifrc but dont find it. :(

[@johnycash978]

I've a display with % gage box says dh30 and I see dh20 on the bottom 23wh 5500 Mah 650A 0.1-0.15 mm with an 3a type C and looks decent it's new sadly every click it does short out shut down and I have to power it again now I feel like I got really pricey 5k mah power bank that generate 1a now I feel shit xd any ideas what might be the cause of that before I go to returns I don't have too much time to dig in it tanks if ya got any ideas

[@CraigOverend]

Careful where and how you store these. Emily and Clarke's Adventure recently interviewed a sailor that had bought a brand new battery powered spot welder off Amazon (they didn't say which brand/model) and stowed it away the night they unpacked it on the boat, only to wake to flames from the area they stowed it. The boat burnt and sank.

[@KerryWongBlog]

Wow!

[@Stevesbe]

I had one it worked a few times then I turned it back on it beeped continuously and wouldn't stop I didn't get to build a battery pack with it

[@cougar1861]

What type of welding could be done on the maximum setting #9?

[@KerryWongBlog]

Perhaps with thicker nickel strips? You don't need to go above #3 for typical use otherwise you will burn holes through the strip.

[@jaro6985]

They say max 0.15mm thickness, so yes thicker strips. But, often you are welding to 18650 cells which will sink a lot of the heat out. From my testing, #9 setting is barely enough for that, although my technique may be bad.

[@cougar1861]

Thanks Kerry Wong & Ja Ro.

[@xyloeye]

Kerry, do you think there's difference between AC vs DC on battery welders? I built the usual microwave welder and have trouble getting the weld to stick regardless of the pulse time.

[@KerryWongBlog]

Current is the most important factor, you can probably check the current at the secondary of the transformer. When shorted you should get 300 to 500 Amps.

[@xyloeye]

@@KerryWongBlog I didn't think of that. I'll check it. Thanks, Kerry. Ken

[@davidahmad6090]

Thanks Sir a very informative video, great work.

[@johnperry5960]

Great review, this is something I've been looking for. Can you keep this plugged in constantly to its power source while using it?

[@KerryWongBlog]

You sure can.

[@IrishFuryan]

@@KerryWongBlog i burnt one of the mosfets of this by keeping it powered using an 18650 charger with a USB out.

[@justsrad]

Thanks for the Vid. Interesting demo indeed. A quick question, why wouldn’t the high current of the welder kill the battery (risk of explosion)?

[@SolarMinerPH]

Are you asking about the cell being welded? Well the current is not flowing through the cell. The current is only flowing between the nickel strips and the metal underneath the nickel strip.

[@justsrad]

@@SolarMinerPH Got it.. thanks :-)

[@KetansaCreatesArt]

I have the 12v input BFIRC circuit board with one led that changes colour according to set levels. Which battery should I attach to it? Can I use the 3 cells 12v 18650 battery pack without BMS?

[@SolarMinerPH]

A high discharge rate lipo battery that is usually used on RC stuff is better than 18650s as they can provide higher current.

[@KetansaCreatesArt]

@@SolarMinerPH , Alright thank you for reply 😊

[@Elektronik-EXTREM]

very nice, interesting video! I find the method of measuring the welding current very imprecise. at 300A and the short welding pulse it shouldn't weld. I would have been interested in how high the voltage at the gate of the MOSFET'S is at the moment of welding. According to the data sheet, 4V is not enough for the transistors to control properly. Can you explain that to me plausibly?

[@foxabilo]

There is a small boost converter on that circuit that ups the battery 3.4v to around 10v

[@georgesmith8988]

Could the first pulse be detecting the application of the probes? Can you tell me the the nickel strip thickness you were using?

[@davidnewton3064]

Given your measurements and the internal battery capacity, how many welds can be performed on a single charge? One Amazon review mentions only 30 welds per charge. It didn't say at which power level. Even at level 9 I can't see this only doing 30 charges. I was going to purchase this but want to confirm battery life.

[@foxabilo]

I get about 800-1000 welds per charge.

[@repairman2be250]

@@foxabiloWell, you are super lucky.

[@amk1108]

Thank you for this review

[@gamerpaddy]

unfourtainly this dc-dc converter ic is not capable of boosting if the battery voltage goes low enough. i have the same thing but if the battery is not fully charged, it turns off at the highest power. i tried adding a cap at the output of the boost converter, but it wouldnt start up then. i added a diode between the battery and the converter together with a big cap so it can keep running if the battery sags a lot, didnt work either. the lowest voltage this thing can run is not low enough to allow for the forward voltage drop of the diode. only solution would be a sepperate 5v supply, probably fed in to the usb port. if the 5v line drops too low, the fet gates wont be charged enough and the rds(on) gets too high, this causes them to blow up sometimes.

[@KerryWongBlog]

The welding portion does not use the DC-DC converter (that is for the battery bank 5V output), I think the issue is what I mentioned in a response to another post earlier. When the battery is not fully charged the internal resistance is high enough and cannot sustain the current for the pulse duration. What you could try is add a resistor and capacitor to the VCC pin of the MCU so that the RC constant is larger than the pulse duration. If the MCU is capable of "soft start", this could be a viable solution.

[@yankey4]

I found they say you can have it plugged in when using. This works well for me. Made a 12s 40p pack. With just stopping for about 20 mins to let it cool off. I did endup running a small shop fan as I was using it. I would think most guys are not going to even us it as much as I have. Maybe this info helps.

[@souza1515]

I would like to know, what is the minimum and safe voltage that I can use it, before having to recharge?

[@gamerpaddy]

ideally fully charged. when your welds dont stick anymore, its time to recharge. 3.8v and above.

[@souza1515]

@@gamerpaddy thank you so much 👍🏻

[@anakuper5120]

Great video just subscribe to your channel, in the last of the video, you said the battery will deteriorate as aging and increase internal resistance, the producer should include supercap in the internal, but they wont as it will increase cost", could you make video about hack this dh20? to use supercap and external RC battery? That would prolong the usability of dh20...

[@hayrettinyayan746]

nice explanation thank you

[@thequinnreapernovaco.7497]

Great video! Would it be possible to remove and replace the built-in Li-Ion battery and simply apply 3.4v to the appropriate inputs with a DC power supply? I suspect the DC power supply (and wiring) would need to handle the current draw requirements. Any idea what might be, given the battery pack that came with the unit?

[@KerryWongBlog]

Typical PS would not be able to supply the 300A-600A required by the welder unfortunately.

[@thequinnreapernovaco.7497]

@@KerryWongBlog Gotcha. It’s amazing that the small Li-ion battery inside can provide that much current! By chance did you happen to see what the battery specs were apart from voltage? mAh, C rating?

[@KerryWongBlog]

@@thequinnreapernovaco.7497 Unfortunately there's no marking on the battery at all.

[@thequinnreapernovaco.7497]

@@KerryWongBlog Thanks, I appreciate the info.

[@pgpilot3884]

Specs device say 5500mAh 650A peak, so theoretically the LiPo's inside can deliver around 120C peak and are high C-rated ones.

[@injoelsgarage3934]

Thanks, Kerry! Got to get one! You r

[@injoelsgarage3934]

You rk k!

[@KerryWongBlog]

Thanks Joel! You are welcome!

[@paullelys161]

Why don't you weld it to a battery like most people will use it for?

[@SlinkyStoney]

I was surprised that the MCU did not hiccup during the spot welding process.

[@KerryWongBlog]

I suspect that the internal resistance of the battery is extremely low. I would like to see how it behaves after hundreds of cycles. If the battery internal resistance increases significantly, it will not be able to deliver sustained high current and will almost certainly cause the MCU to brownout.

[@SlinkyStoney]

@@KerryWongBlog yeah, was thinking about that too when the battery reaches about a hundred cycles. Maybe a capacitor near the MCU supply pin might help avoid the brownout or some of the large ceramic caps on the board are already doing it.

[@SeanBZA]

@@SlinkyStoney The boost converter will definitely be the helper, the 5V supply, with those large ceramic capacitors, will hold up the output for the pulse duration, and so long as the battery is held near a fully charged state it should have no problems as it ages. At least the cell is easy to change, that size pouch cell is a common item, and pretty much any RC model battery can be used to replace it.

[@perhansen3959]

100 welds and its done