Sunkko 788H FIXED [battery tab welder] (041) 

Id rather it be 220v, throw a spare dryer cord on it and go to town..

felix991 You are correct thank you I was using the regular 15 amp and it was popping so I connected it to my air-conditioning 60 amp and it worked fine

Totally. Yeah, very easily, and I even think I will do that as I have a gigantic battery build planned for this year which is impossible to do with the machine as is. The wires from the transformer are screwed in on the back of the bus bars that the actual welding pins are attached to, so you can simply extend the wire and make a little handheld grip for those pins.

No, the primary is still the same, I just changed the secondary. That shouldn't change the primary inductance (appreciably). I haven't switched out primary and secondary.

It works very well for me with 0.15mm nickel strips on 18650s. No good welding means the current is too low, so you either have too many secondary windings (too high voltage, not enough current) or too few (too high resistance in the secondary for the voltage available). Try one more or one fewer turn. You may also be saturating your transformer if you are using a transformer that is too small. Compare it to my size transformer in the video.

+PowerElectronicsBlog I've done 3 windings. Have you got à mail please ton send you à picture ? Thanks

Try first to do another winding. Pictures won't help here; it's just one variable you have to change.

PowerElectronicsBlog

did you get it to work?

Yup, same as always. Although I don't use it anymore, the push-up functionality kind of works better for small packs.

Ahoj Oliver, práve bojujem s rovnakým problémom pri mojom sunkko 737g, bol by som vďačný za akúkoľvek radu pri výmene alebo modifikácii pôvodného transformátora a spojazdnenia tejto mašinky na 230V/25A.

No, a decently built transformer has what's called a bobbin on the inside separating the primary windings from the core. The core is also always connected to PE (protective earth), i.e. even if there is somehow a connection to live, it will cause your GFCI to trip well before there is any danger. The same applies in the tab welder: there is a hard connection from ground to the transformer core. You still always have to be careful when dealing with mains voltage, notwithstanding. The secondary is indeed 4VAC, i.e. 6ish volts peak. And yes, I'm talking about a 190:3 ratio. Using a magnetron transformer in reverse roughly attains that ratio. In this case, though, the high-voltage secondary was completely cut out of the transformer and replaced with the thick wire, so the original 240V primary is still there.

Thanks PEB!! I ordered one of these 988H and it arrived about 3 days ago. I turned the weld power on, and everything was fine..... well.... for at least the first few goes. But then after that, the home breaker drama started up heheheh. I confirm with you and the others that the stock transformer has too low a turns ratio. The stock transformer has two extremely thick wire cables (ie. the weld cables) coming out of it, together with two (much lower amperage) black coloured wires on the same side. I need to get in there with a meter and check out what these two black-coloured wires are (on the same side as the thick weld cables). I'm predicting that you needed to disassemble the unit (springs etc) in order to remove the weld cables from the internal terminals (holes) of the rectangular metal weld-arms. I ordered a new microwave oven transformer which will be modifiable. I'm thinking of reducing some coil turns of the thick 'weld cable' side in order to 'increase' the turns ratio - to achieve about 60 to 1 turns ratio. On the other hand, if the stock microwave transformer (that came with the 788H) is modifiable (and it looks like it might be modifiable), I will try to do what I had said to the stock transformer. That is, remove some coil turns of the thick wire side. Anyway, the videos you made were great. It really helps others to understand the reason for the crazy home-breaker tripping. The people that designed the 788H need to fix up their design!