Spot welder

[armandine2]

... just followed Artem Kositsyn83 on YouTube for his Fnirsi SWM-10 settings - worked well on coin cell batteries with supplied reel of nickel plated strip. 

[DisasterNow]

I'm glad you had a positive experience with fnirsi. This brand was not recommended to me, and I bought the UF2oB with supercapacitors.

[voltsandjolts]

... just followed Artem Kositsyn83 on YouTube for his Fnirsi SWM-10 settings - worked well on coin cell batteries with supplied reel of nickel plated strip. 

Fnirsi quality is variable, but I agree the SMW-10 is fine for smaller jobs such as coin cells and smaller/lower current 18650 packs. I've rebuilt 9 camera 18650 packs and it's done the job well enough. For larger or higher current (thicker nickel strip) packs you need something bigger though.

[DisasterNow]

I don't have any product of Fnirsi, but I understand that they're not concerned about whether they can do the job, but rather the safety of their products.

-------------------------

Returning to spot welding, I was intrigued by the setting for performing two consecutive welds on the same spot on the material (my model performs a maximum of two, but I believe almost all models have this setting).
Do you have experience with this function? Is it useful to ALWAYS perform a "double" weld?
And if it were useful, I imagine the interval between the two consecutive welds also plays a role: on mine, it's adjustable from 1 ms to 2 seconds. The only thing I can think about is whether it's better for the area to remain hot, or to cool briefly between the two welds.
Any input?

[voltsandjolts]

I don't have any product of Fnirsi, but I understand that they're not concerned about whether they can do the job, but rather the safety of their products.

Do you mean there have been safety issues with Fnirsi spot welders?

Can you please provide a link to the safety issues you mention.

[DisasterNow]

Do you mean there have been safety issues with Fnirsi spot welders?
Can you please provide a link to the safety issues you mention.

Mine was just an observation I learned here on the forum, where many users talk about the unreliability of some Fnirsi products. I have no direct experience.
I just reported what I have heard several times here on the forum.

[BradC]

Returning to spot welding, I was intrigued by the setting for performing two consecutive welds on the same spot on the material (my model performs a maximum of two, but I believe almost all models have this setting).

This is probably AI slop (or an Ad for Sunstone), but it does explain at least the theoretical rationale for dual pulse : https://themakerschest.com/blogs/spot-welding-hub/single-pulse-vs-dual-pulse-spot-welding-why-it-matters-for-battery-tab-quality

I started with a cheap single pulse unit and my current unit does dual pulse. To be honest I don't think I've really noticed a difference.

[DisasterNow]

This is probably AI slop (or an Ad for Sunstone), but it does explain at least the theoretical rationale for dual pulse : https://themakerschest.com/blogs/spot-welding-hub/single-pulse-vs-dual-pulse-spot-welding-why-it-matters-for-battery-tab-quality

I started with a cheap single pulse unit and my current unit does dual pulse. To be honest I don't think I've really noticed a difference.

I honestly thought they were two pulses of the same power, but reading the article in the link above, the first pulse has a lower power, to prepare the welding area, while the second pulse performs the welding.
I don't know how reliable this link is, but if it were, there would basically be no reason to weld with a single pulse... (for those with a two-pulse welder).
Thanks for your contribution

[voltsandjolts]

Do you mean there have been safety issues with Fnirsi spot welders?
Can you please provide a link to the safety issues you mention.

Mine was just an observation I learned here on the forum, where many users talk about the unreliability of some Fnirsi products. I have no direct experience.
I just reported what I have heard several times here on the forum.

You have raised safety concerns about Fnirsi products that I own.
Please link your sources so I can judge the risk.
Or are you just exaggerating some reliability issue that is not a safety concern?

[DisasterNow]

I've already answered this: I've read several times here on the forum that these are low-cost products that raise some questions. I have no personal experience; in fact, in my first post in this thread, I considered purchasing a spot welder from that brand. Again, based on my personal experience, these are products I'm not familiar with, but there are often poor reviews for them, for example, here on the forum. Personal opinion: continue to use your spot welder without any problems.

[BradC]

This is probably AI slop (or an Ad for Sunstone), but it does explain at least the theoretical rationale for dual pulse : https://themakerschest.com/blogs/spot-welding-hub/single-pulse-vs-dual-pulse-spot-welding-why-it-matters-for-battery-tab-quality

I started with a cheap single pulse unit and my current unit does dual pulse. To be honest I don't think I've really noticed a difference.

I honestly thought they were two pulses of the same power, but reading the article in the link above, the first pulse has a lower power, to prepare the welding area, while the second pulse performs the welding.
I don't know how reliable this link is, but if it were, there would basically be no reason to weld with a single pulse... (for those with a two-pulse welder).
Thanks for your contribution

Yes, I tend to set the first pulse about 10% of the second pulse duration. I tend to go with 2 & 20ms and control the weld power with the voltage instead.

[DisasterNow]

Yes, I tend to set the first pulse about 10% of the second pulse duration. I tend to go with 2 & 20ms and control the weld power with the voltage instead.

Which spot welder do you have that allows these double-pulse welding settings? With my welder (UF20B), I only have one adjustment for double-pulse welding: the time between the first and second pulses (from 0.1s to 2s). No other settings are possible.

[DisasterNow]

I started doing some spot welding tests on some used battery packs (image attached). The laminations in question are 0.15mm thick. I'm doing fairly good soldering on the battery terminals with the settings I used (the lamination isn't very tight because there were residues of old solder underneath).
However, I had a problem soldering the third lamination, which would then go to the cable leading to the PCB: I used the same settings, but it's clear that it soldered too much, almost piercing the lamination; But above all, it's clear that the welding is also damaging the casing of the batteries underneath (in fact, I could smell burnt plastic after welding; it probably melted the film covering the 18650s).
I'll venture some solutions:
.Weld the top sheet first, and then solder everything to the batteries.
.Lower the power (but the solder might not hold).
.Increase the thickness of the solder in the area where this sheet is welded, placing a third, thicker sheet between the two batteries (which will act as an insulator to prevent the solder from reaching the battery body).

I'll definitely have to practice more.

I'll add: looking closely at the photo, you can see that the solder toward the battery's positive terminal came out better, while the solder toward the negative terminal is "burned." I think it's because there's green insulating paper between the two metal sheets and the positive terminal, while there isn't any on the negative, so the solder reached the battery body.
Perhaps a solution would be to place a piece of green insulating paper under the entire solder area of ​​the third metal sheet...

[elektryk]

That's normal, just weld third strip on positive or negative terminal. You can also use shaped strips.
BTW spot welding and soldering are 2 different things.

[DisasterNow]

I'll have to find a solution, because the spot weld on the top plate (the one toward the right negative pole) has reached the edge of the battery body. I think a piece of green insulating paper placed between the two batteries might solve the problem (but it will also reduce the discharge output power).

[BradC]

Which spot welder do you have that allows these double-pulse welding settings? With my welder (UF20B), I only have one adjustment for double-pulse welding: the time between the first and second pulses (from 0.1s to 2s). No other settings are possible.

I use a KEKK K100 with 12 fets. Modified with a mosfet driver, decent flyback diode and a fat TVS across the cables. I drive it from a 6S 3000F “Maxwell” (or maybe the factory was on Maxwell st, who really knows what’s under the blue heatshrink) supercap bank that I run between about 8 & 12 Volts depending on the material. I’ve had more than 2200A out of it, so while they were cheap they do pack a punch.

I can individually change the pulse times and time between pulses. While I could go as high as 15V, past about 12V the back emf from the leads tends to cause expensive silicone flavoured smoke so I stop there. Most packs I make are just .15 pure nickel and I can weld those perfectly at 8V with a 20ms pulse. 11V just blows holes in them.

Edit: as for the photo there. I always pre-weld the take off strips on the bench before welding the remainder to the battery. I use a stainless steel ruler as a backing plate to weld on. First time I built a pack I shorted a cell and it vented like a flame thrower. Not an experience I’m keen to repeat.

[DisasterNow]

Which spot welder do you have that allows these double-pulse welding settings? With my welder (UF20B), I only have one adjustment for double-pulse welding: the time between the first and second pulses (from 0.1s to 2s). No other settings are possible.

I use a KEKK K100 with 12 fets. Modified with a mosfet driver, decent flyback diode and a fat TVS across the cables. I drive it from a 6S 3000F “Maxwell” (or maybe the factory was on Maxwell st, who really knows what’s under the blue heatshrink) supercap bank that I run between about 8 & 12 Volts depending on the material. I’ve had more than 2200A out of it, so while they were cheap they do pack a punch.

I can individually change the pulse times and time between pulses. While I could go as high as 15V, past about 12V the back emf from the leads tends to cause expensive silicone flavoured smoke so I stop there. Most packs I make are just .15 pure nickel and I can weld those perfectly at 8V with a 20ms pulse. 11V just blows holes in them.

Edit: as for the photo there. I always pre-weld the take off strips on the bench before welding the remainder to the battery. I use a stainless steel ruler as a backing plate to weld on. First time I built a pack I shorted a cell and it vented like a flame thrower. Not an experience I’m keen to repeat.

Ok, so you have a very customizable spot welding system. Truly excellent.
For my spot welding test, I had thought about first welding the tabs that detect the voltage of the various cells, but the procedure would then require welding the wires to the tabs, and I think that could overheat the plastic battery case, for example. Instead, I first welding the individual tab to the wire, and then spot-welded the tab over the positive-negative connection plate.
I want to try placing a layer of green insulating paper between the batteries and the plate that joins them, and then weld the other plate in the center.

[elektryk]

It will burn green paper underneath because of low thermal mass of steel strip.

That's better idea:

Edit: as for the photo there. I always pre-weld the take off strips on the bench before welding the remainder to the battery. I use a stainless steel ruler as a backing plate to weld on. First time I built a pack I shorted a cell and it vented like a flame thrower. Not an experience I’m keen to repeat.

[DisasterNow]

I agree, mine wasn't a good idea. Also because I've seen in other tests that the green paper turns practically brown after spot welding (the beginning of a fire). I'll do some tests by joining two 0.15mm thick sheets of metal (I'll definitely need to reduce the power I use when spot welding it to the battery terminal). I'd also like to figure out a suitable support surface; I'll need some thick stainless steel sheets anyway.

[DisasterNow]

I'm reporting what Brad wrote, in light of some of my tests:

I always pre-weld the take off strips on the bench before welding the remainder to the battery. I use a stainless steel ruler as a backing plate to weld on.

I tried spot welding two 0.15mm thick nickel-plated steel sheets, one on top of the other, on the bench. I started using a stainless steel plate as a support, but I noticed that the weld also penetrated the underlying plate, so to remove the two sheets, I had to use pliers (this even at low output power, 20%); perhaps the metal material of Brad's ruler was different.
I then tried using a piece of hardwood as a support, but obviously it smoked and blackened.
Finally, I used a ceramic tile as a base, allowing me to lift the two sheets without any problems.
I wanted to ask a question: in spot welding like this, where I simply had to join two sheets together, could the material of the support (ceramic, metal, or wood) affect the path of the electrical discharge?

[BradC]

Nickel plated steel isn’t going to be significantly different to stainless in resistance I suppose. I only use straight nickel strips and have never had one stick to the ruler. The ceramic is a great idea. I’m going to grab a spare tile out of the shed. Much better than the ruler.

[DisasterNow]

I don't have any other materials to spot-weld, only nickel-plated steel strips, so I can't experiment with other metals.
The tests certainly helped me realize that if I spot-weld a 0.15mm sheet metal to a battery terminal, I can use a power output of up to 35%. However, if I spot-weld two insulated 0.15mm sheets, it's easy to pierce the supports even at 30%. At 20%, however, I see that the work is satisfactory.

From initial testing, I found the ceramic support base to be good for spot welding two metal sheets.
What I was wondering, however, is whether using a non-conductive surface (ceramic, wood) or a conductive one (e.g., stainless steel) as a support surface might affect the spot welding. I still have to run some tests, but I had the feeling, with the same settings, that the two results were slightly different. But I could be wrong. I also found it very convenient to have a nice flat support base, like tile, for straightening the metal sheets properly (with a rubber mallet).