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Which spot welder control board to use?
#1
I have recently obtained a 240v 1100w microwave oven transformer to make myself a spot welder for battery packs.

There are a few different controller boards available and I am looking for some pointers on selecting which control board to use.

There seem to be 3 main ones available

The cheapest one seems to be
Geekcreit® NY-D01 40A/100A Digital Display Spot Welding Module Time and Current Controller Panel Timing Ammeter Spot Welders Control Board - 100A
I think this is single pulse and comes in "40A" for AU$14.89  or "100A" for $19.36
https://www.banggood.com/Geekcreit-NY-D0...rehouse=CN

Then there is this one
100A LCD Display Digital Double Pulse Encoder Spot Welder Welding Machine Transformer Controller Board Time Control Module
for AU$40.24
https://www.banggood.com/100A-LCD-Displa...rehouse=CN

Or this one:
NY-D08 100A Spot Welder Controller Welding Machine Pneumatic Color LCD Display Multi-point Personalization with Temperature Sensor
also $40.24
https://www.banggood.com/NY-D08-100A-Spo...rehouse=CN
This one has a colour screen.
It also seems to add a temperature control - but I am not sure how that works with the rest of it?
It also talks about "no external power supply', but the diagram shows a 9-12v AC transformer?
It also says "pneumatic control", but I am not sure what that is for?

Then there is
https://www.ebay.com.au/itm/220V-Spot-we...3114770145
Which seems to add a heatsink and transformer

Has anyone used any of there these?
Does anyone have some ideas on which to choose?
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#2
I used a JST41-1200 Battery spot welding control board, 16 single chip microcomputer control, 1602 MCU LCD, encoder double pulse pcb to control the pulse duration. https://www.aliexpress.com/item/32810563725.html

Striped out an old 230V 850W microwave oven i had kicking around to salvage the transformer, cut out the secondary windings and removed the magnetic shims i replaced the windings with two turns of 16mm2 flexible battery cable with approx 1M of spare cable to exit through the case for each of the spark electrodes.

I mounted the MOT in the case along with the pcb and used a small 230V to 12V transformer for the pcb power supply. Cut the end of the case out and fitted an old PC fan on the end to keep everything cool, not that anything gets hot, I probably didn't need the fan. Pushed the battery cable out through a couple of holes drilled into the front of the case and cut holes for the display board and adjustment knob.

I soldered a couple of soldering iron tips into the ends of the battery cable for the electrodes and covered the ends with a few layers of heat shrink.

Used an old sewing machine peddle switch to operate the welder.

It works very well for welding fuses to cells with pulse power set to about 80% but I do need to have the pulse power set to 100% if I'm welding nickel strip otherwise the weld isn't strong enough.

I have now obtained a 1000W MOT that I'm going to fit in at some stage. I will take a few build photos when I get around to doing it.

I haven't measured the output amperage but I would imagine it's around the 450A mark, the voltage at the electrodes around 1.8V

I found that a two pulse weld works well on the fuses, P1 set to 65% for 70ms (to pre-warm the metal) a 25ms delay and P2 set to 80% for 90ms (for the weld).

The only purchases i made was for the JST41-1200, 230V-12V transformer and 2.5m of 16mm2 battery cable, the build cost was around £35 and a few hours of my time.
UK Southwest.

7 kWp Solar Panels (28 x 250Wp Shinetime Mono).
14 X APS YC500i Micro Inverters.
28 X 40P 18650 cell packs/modules configured as 14S 80P.
Sofar Mass Energy ME3000SP AC coupled charger/inverter.
Still sourcing and processing cells for powerwall.
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#3
Thank you for the comprehensive reply chuckp!
It was actually a post of yours elsewhere on the forum that inpired me to go down the DIY spot welder path - so thank you for that too.
I definitely want to weld nickel strip. Do you think the bigger transformer will make a difference to how well that works?
I have not seen the JST41-1200 on either eBay or banggood (I have used these 2 marketplaces) and the ad you linked to says
"There are slight welding marks on the circuit board, which do not affect the use of the product. Please don't buy it if you mind"
Which makes me a bit wary that it might be used?
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#4
(10-23-2019, 11:01 AM)Oz18650 Wrote: Thank you for the comprehensive reply chuckp!
It was actually a post of yours elsewhere on the forum that inpired me to go down the DIY spot welder path - so thank you for that too.
I definitely want to weld nickel strip. Do you think the bigger transformer will make a difference to how well that works?

Most defiantly I'd go with the larger MOT, mine is prefect on my fuses but it does struggle with nickel strip sometimes.
I think pure nickel strip vs the nickel plated steal makes a massive difference too.

(10-23-2019, 11:01 AM)Oz18650 Wrote: "There are slight welding marks on the circuit board, which do not affect the use of the product. Please don't buy it if you mind"
Which makes me a bit wary that it might be used?

I've had a fair bit of stuff from Ailexpress and so for everything has been great.
The board i received was defiantly new not used.
I think they are marks made during manufacturing so not A grade then they sell them off a litter cheaper
UK Southwest.

7 kWp Solar Panels (28 x 250Wp Shinetime Mono).
14 X APS YC500i Micro Inverters.
28 X 40P 18650 cell packs/modules configured as 14S 80P.
Sofar Mass Energy ME3000SP AC coupled charger/inverter.
Still sourcing and processing cells for powerwall.
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#5
I ended up purchasing one like this.

https://www.banggood.com/100A-LCD-Displa...rehouse=CN

Now to wait for it to arrive....
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#6
It wasn't my original idea, I had help from old timers who figured I could try building a spot welder out of a microwave the same way they build them commercially. But, 12 or so years ago I popularized MOT-based spot welders. Almost everyone on the net who's heard of them, has heard of them because of me. Either because of my written tutorials, or later my Youtube tutorials, or later, the tutorials of bigger Youtubers who asked me for help. :p. The idea came about because I wanted to create a welder that welded chainmaille rings, and the existing welders were terrible (also because of my design, there's now chainamaille ring welders sold by the big supply companies.. I know this, because they told me they made them because of me Smile ).

It's awesome to see that there are companies manufacturing spot welder timers for the DIY community, because MOT-based spot welders are so popular that there's actual demand for that.

Back in the day, this was not a thing you could buy. So I made my own out of the TRIAC from a microwave oven, a 555-timer chip, some junk components I pulled out of old VCRs, a cell phone charger, and some old amplifiers. Stuffed it all into a CD-ROM case and gave it a cover from the fake wood on the front of an old record player.

So, I technically built it for free, from junk Big Grin

I have pictures of it around somewhere... *digs*...



- I knew how to create circuit boards, but didn't have any copper blanks or etchant.

- I forget what it all does, I know there was a pushbutton that overrode the timer circuit and just acted like a switch. The speaker terminals in the back were so that you could swap out the timing components (resistors and capacitors that determined the bulk timing scale). One pair was to add a foot pedal trigger instead of the trigger button. I think there were three sets of timing triggers on the front, the two small knobs and the big precise knob and a selector switch to switch among them (in chainmaille, it's common to rotate between 2-3 different wire sizes back and forth when making jewellery, so instead of having to crank the knob every single weld to set it up for the next wire size, I just gave it 3 knobs you would set correctly at the start of a project, and then switches to jump around to which knob was active).

- Yes that's hot glue, not silicone. I'd never used silicone, but I did have hot glue.

- Yes, that heatsink on the TRIAC is comically undersized, meant for a TO-220, not a 15A TRIAC. And yes I didn't have any small bolts, so it's afixed with copper wire like it's a hay bale.

Really the whole thing was just as ghetto as could be. But I had zero budget and online electronic suppliers were just starting to appear (as in, I found a good deal on LEDs on eBay, bought 2000 of them and split them among 20 guys all around the world... for LEDs, something anyone can order in any quantity they want nowadays, for nearly free).

There was an ugly period between the death of Radioshack and the creation of the online small-scale electronic suppliers.





I luckily realized, "A tutorial using a 555 timer chip is going to be obsolete as soon as it's made, don't write one" and never did :p

$15 for something that shows up at your door sounds like heaven. Do that. Don't do what I did.
Oz18650 likes this post
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#7
I found a neat looking DC based spot welder --> https://www.aliexpress.com/item/40004203...b201603_53

or

https://www.aliexpress.com/item/40003641...b201603_53

or

https://www.aliexpress.com/item/40004248...b201603_53

I was wondering what people think about this or similar units.
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#8
Still waiting for mine to arrive
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#9
Just curious, why go this route vs a malectrics or Kweld? It seems like it's not worth the effort considering how the other options are basically plug and play - and with a large community with lots of useful info about both units.

As for the DC welders you linked - the malectrics or Kweld units look like a much better option. They look seriously under powered for what they are doing, with not nearly enough heat sinking. Also, they don't seem to be adjustable in any useful way. You will need to adjust current depending on what you are welding, and to what. Different cells will respond differently - another reason I would go with the german units
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#10
The main reason I chose this path is price.
Yes it will be more effort, but I don't think too much.
I am also hoping to contribute my experience with this to the community and give some insight into what works or does not work.
I did look at the malectrics and kweld and they seemed like good products, but I would need to buy the welders and a high current battery to power them.
I think this way should be significantly cheaper. Hopefully the results are still good.
The controller board was cheap (AU$30) and the microwave oven transformer was free from a discarded microwave oven (I even have another as a spare)
I still need a few bits:
-secondary winding wire, which will be recycled
-9-12v transformer - I think I should be able to find one of these.
- flexible leads - not sure where these will come from
- tips - not sure where these will come from
There is probably very little cost in those other parts, so it should end up very low cost.
My controller board finally arrived yesterday!
I am still a fair way off from spot welding packs together. I still have to wait to check for self discharging cells, then capacity test, so I have plenty of time to get the spotwelder set up.
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