Spot Welder

[Willy]

Just tested mine out today too. Can't really expand on fixerdave's review, it was very good.

I agree that I had it turned up most of the way, and it wasn't like it was burning holes or anything. It
did it's job pretty good, not great.

Oh .. and to answer Willys question ... NO it does not stick very far out so I am going to have to
extend them somehow because ... well here is a pic of the pack I am building.

You may have learned this already but I would be remiss if I did not pass it on. Having looked at a number of reviews of various battery spot welders both factory made and DIY versions, one thing I noticed that was mentioned by several users was the importance of the amount of down force applied while performing the spot weld. Several builders and reviewers stipulated that it was the difference between success and failure. Apparently the amount of pressure is key to making it work.
When one thinks of what is happening or supposed to be happening in the electrical circuit during the spot weld it only makes sense.

Also an item of note, I spotted a model very similar to yours but with a slightly higher rating and the added benefit of a hand held wand. The rating when used with the hand held wand was slightly lower than when the unit used the built in electrode holders. You may want to be aware of this if you decide to go that route.

That is a big battery pack you're building, I hope you get the details sorted out to your liking.

[fixerdave]

The one in the first video clearly must have been timed, because the setting the reviewer did seemed to make a difference. Probably it would take a 'scope to see the actual system. They have a display showing 99 levels, which they would not need if it was fixed, and there is a separate display showing setting of 1 or 2 pulses... The triac would allow any amount of a half cycle to be included in the pulse, up to maybe 85% or so.

The "99" is 99% of full "current" according to the manual. The other 2-digit display says either "1P" or "2P", nothing more. The "*" sets, running through the 3 active digits on the 2 displays like a cheap watch.

But, as you say, if they are just turning the triac on sooner or later to regulate current then the "current" display is as much pulse width as anything else. Glorified single-shot light dimmer circuit Well, double-shot including their 2P cleaning cycle.

It would also explain why the manual repeatedly mutters about not using "active" outlets. If the input wasn't a decent sine wave, it would muck the timing.

2x 7-segment LEDs to indicate what could have been shown with a single LED, or the dot on the other display, seems odd... almost like a broken promise. I guess I was expecting something a little more sophisticated, but it gets the job done.

David...

[J Tiers]

I notice that the chinese vendors are kinda big on the added bling of extra displays. They may not have good features on a minilathe, but by golly they can read you out the RPM to single digits on some. even if the lathe does not work well at that rpm.

So lighting up 2 digits to tell you the pulse setting is way better bling than just having a switch to point at a '1" , or a "2".

You may have learned this already but I would be remiss if I did not pass it on. Having looked at a number of reviews of various battery spot welders both factory made and DIY versions, one thing I noticed that was mentioned by several users was the importance of the amount of down force applied while performing the spot weld. Several builders and reviewers stipulated that it was the difference between success and failure. Apparently the amount of pressure is key to making it work.
When one thinks of what is happening or supposed to be happening in the electrical circuit during the spot weld it only makes sense.
......

What I learned in running the aluminum spot welding production was that yes, pressure is key. You want the energy to go into the metal, and not be dissipated in sparks and arcs at the contacts. ideally, you should barely be able to tell the weld occurred, there should be no drama, no light show. Then the energy is all going into melting metal together.

That usually means a pretty good amount of pressure, because there are three contacts in a regular "tong" spot welder, and four in the battery welder. The battery welder has electrode to strip, strip to case, case to strip, and strip to other electrode (the tong welder does not have anything equivalent to the second case-to-strip contact). All of those need to be good low resistance contacts, so that the energy goes into the resistance of the metal, heating it.

Pressure should not be crazy high, because that also can make a bad weld, there is a wide range of "ok" that you need to be in.

Some of the videos I looked at would have one of the electrodes give a bright spark during the weld.... that is probably wasting energy, and makes inconsistent welds, because the amount of energy going into the weld is not always the same.

Does that thing have independent pressure on each of the electrodes? I thought I saw that it did, but am not sure.

[Mike Amick]

one thing I noticed that was mentioned by several users was the importance of the amount of down force applied while performing the spot weld. Several builders and reviewers stipulated that it was the difference between success and failure. Apparently the amount of pressure is key to making it work.

ah .. your right on again Willy. When I was first testing it I started out low on the amperage and pulse and worked
my way up. When I was about turned up full it still was barely welding.

I was pretty worried, but remembered the pressure dial and .. yes .. it made all the difference. I think that
will be an advantage with the pedal. You can push it past where it would normally trigger but it will wait till you
push the pedal effectively allowing you more pressure.

My main worry as my pic showed is that its not even close to the middle of my pack, so I will be extending the
electrode bars out another 2" or so.

Thinking of looking for a solid copper bar and drilling a whole through it and bolting it to the current bars.

[mattthemuppet]

any update Mike? Has the welder held up? Did it make good welds? Any tips or info appreciated as I'll be rebuilding my bike battery this summer.

[Mike Amick]

I'm satisfied.

The extensions worked great. If you look at the pic you can see the tops of the electrodes sticking pretty
far up in the air. What I did was take a non conductive "thing" ( I used a plastic jar bottle cap ) and used it
to push down on the tops of those electrodes putting pressure on the "spot", then push the peddle down making
the weld.

I always did two and sometimes three hits, just for insurance.

Considering I didn't pay more than about 15 bucks for all the batteries, I'm happy.

I did learn about torque arms while putting my bike together, totally ruined a set of forks
The motor mounting wants to spin with any amount of power.

Anyways, I would buy the welder again.

[mattthemuppet]

thanks Mike, I appreciate the feedback! That's a serious looking battery you have there Did you get the BMS issue solved? $15 for all those batteries is a steal. I'll be getting mine "new" (unused but pulled from packs) for ~$140 for 40, which is quite a bit more, but given how much I rely on that bike I think it's worth the money.

I ended up buying an Arduino based spot welder kit
https://malectrics.eu/product/diy-ar...-lipo-battery/

that plus the LiPo battery from Hobbyking to run came to ~$200, which is more than what your 737G cost, but it has really good reviews and support. The Sunkko welders seem to be a bit more of a lottery, especially on 110V, and I have a limited window when I can get this rebuilt. I'll post a thread when I get it and have had a chance to use it.

wouldn't mind seeing pics of your bike set up. I'm guessing this is a retrofit? Those are always neat to see. Be careful on wet roads or loose trails, mine spat me off in the rain the first winter I got it and the hole in my elbow took a couple of months to fully heal.

[challenger]

I've done this a few times to get the voltage needed - you can do this either by drilling and hacking out the copper winding you want to replace.....or grind out the weld and and it just comes apart.

Also, consider the ballast from an industrial light fixture. They're free or small dollars used (the igniter goes and they're tossed) and are larger. Like the MWT, the advantage is the two windings are separate vs on top of each other so they're easily rewound.

This is for a resistance solderer I'm making

Old post I know but I recently acquired a Keystone MH-1000A-P-KIT that includes a very large ballast. I would love to know what the actual difference is between a ballast ans a transformer because this thing sure looks like a transformer. I've had a MWT sitting around that was going to be my spot welder but I have not tried it out yet and I came across what would seem to be a much higher capacity power source in this ballast. Any help with the engineering and use of a HID ballast into a spot welder is appreciated.
Why are there so many windings for your secondary? I am under the impression that fewer windings = more current?

[challenger]

Ok, here we go. Not pretty but functional.

My memory failed to recall the variation I went through that day. I have 2 1/2 turns of Private Messages wire for the secondary. There's also a winding under it (blue wire) that provides a 12v circuit for the bridge rectifier and the DC solenoid. The "push button" is a metal strip that I tap to activate the solenoid.

Keep in mind this is a Tab Welder meant for welding nickel tabs on batteries and NOT a Spot Welder for welding sheet metal together.

And I can see all the safety police jumping up and down already.

The safety police need to STFU IMO. Let Darwin's law do their job . The unit you built looks great. Please explain how you came to know what winding(s) to use for your 12V.
BTW, always wear safety glasses, a diaper, a condom, safety glasses, a legally filed last will and testament, no puddles of water and take your vitamins before you get out of bed each day. You can thank me later for these rules. Or just go on public radio and listen for me there.

[darryl]

Since this topic came up again, I have a question- for those who have built capacitor discharge machines. Wondering about the capacitor type- it would seem like a low ESR type would be best. In other words, caps made for switching power supplies. In days of old this type was not yet being made, so regular type caps it was. With many caps in parallel, the need for a 'fast discharge' type of cap might not exist- but maybe I'm on to something here. What say you?

[J Tiers]

In the past, many things did not exist. I have a manual for a magnet charger from the 1940s. Magnet charging requires a high current pulse similar to spot welding.

What was done then was to use a high voltage lower current source, with a transformer, and a thyratron (the 'tube" version of an SCR, although not a "vacuum tube"). The thyratron was triggered to provide current to the primary of a transformer, which output a lower voltage but much higher current pulse on the secondary. Various heavy conductors were used to apply the resulting magnetic field to the target magnet.

The capacitor was generally a type similar to present day "motor run" types, with paper and oil insulation. The high current capability was not needed, since the primary side was high voltage and lower current. While not extremely low, the primary side current could be a few amperes, or tens of amperes.