Author Topic: SunkCo 788+ battery welder  (Read 376 times)

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dnix71

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SunkCo 788+ battery welder
« on: August 05, 2014, 06:48:27 PM »
Stick with the 220v 50Hz version if you buy one.
I paid almost double ($200) for the 110v 60Hz version and got less features because the eBay seller lied. The picture in the supplied manual does not match the actual machine. It only shows a single power switch. Mine has two but one doesn't work.

There is supposed to be a variable voltage battery charger one this, but on the 110v it doesn't work. I completely dissasembled it and discovered that the switch to the battery charge circuit doesn't go anywhere.

The only input labelled is "220v" There wasn't a 110v version. The reason for twice the price is someone had to swap out the transformer and alter the circuit board to disable what would not work on 110v.

It does spot weld with a double or single pulse and has a foot pedal if you don't want to use the lift switch. I didn't blow any fuse using it either.

The American style plug is an illegal design and the device is polarized but the plug is not. I will have to fix that. If you plug it in wrong the transformer makes a thunk as it goes live. Turn the plug around and you don't hear the thunk until you flip the main power switch. It really should be grounded, as it has a metal shell. The main welding bars go live briefly when it's plugged in if you plug it in backwards too. The cheap banana plugs that are supplied for the non-working battery charger don't insert fully, leaving exposed pins.

There needs to be an electrical separator between the two bars. I added electrical tape. If you are welding a tab on a AA cell the tips have to be adjusted so close that you could bump bars if you aren't careful.

The welding current was set to 40 amps at the factory and the settings are remembered even if you unplug it. 40 amps (if that's even correct) isn't enough. I max it to 80 and got better results. The hex wrench to lock and unlock the welding pins was the wrong size. It also comes with a flat wrench to hold the pin clamps in place while tightening down on the set screw.

Frank S

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Re: SunkCo 788+ battery welder
« Reply #1 on: August 05, 2014, 08:24:29 PM »
One big problem with a lot of electrical gadgets is if they were primarily designed for the European style voltages then re made to be offered to the US market with our goofy split phase. the wiring inside will meet standards for the lower current highre voltage but when you cut the voltage in half you have to know that everything inside on the input current side needs larger Gage wiring
 I am assuming your machine has only a 2 prong plug, and probably is not a polarized one at that.
 
 I looked at both models and both show up to 15A for the input current . To me that would mean that if the 220 v model could draw up to 15 amps then the 110 v model would have to draw up to 30 amps to have the same output current .
 In my opinion if the draw can be that much then a 30 amp twist lock or a dryer plug should be used on it   
I live so far outside of the box, when I die they will stretch my carcass over the coffin

joestue

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Re: SunkCo 788+ battery welder
« Reply #2 on: August 05, 2014, 11:13:09 PM »
that "thunk" you hear upon plugging the transformer in, is entirely random chance has nothing to do with the wiring.
it is simply the magnetic charge last left in the core, and if its in the same direction the electricity is going when you plug it in, then you get a saturated core within 8 milliseconds.
toroids are particularly messy because the air gap is almost zero.

dnix71

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Re: SunkCo 788+ battery welder
« Reply #3 on: August 06, 2014, 11:41:23 AM »
It is the wiring. The transformer is a laminated iron core cube. It thunks every time it's powered on just like a stick welder with a switch. The transformer is hard wired to one side of the line. The plug is not polarized so there is 1/2 chance of plugging it in hot.

That I will fix today if I have the time. It's going to get the shell grounded, too.

dnix71

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Re: SunkCo 788+ battery welder
« Reply #4 on: August 07, 2014, 07:24:03 PM »
I rewired it according to US standards and now it's worse. If I turn the non-functioning battery charger on it trips my GFCI outlet.


MaryAlana

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Re: SunkCo 788+ battery welder
« Reply #5 on: August 08, 2014, 02:05:12 PM »
Any chance one side of the transformer is grounded to the frame? That would be where I would start with an ohmmeter. Could also be inrush current tripping the breaker.

Frank S

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Re: SunkCo 788+ battery welder
« Reply #6 on: August 08, 2014, 04:35:30 PM »
if you are not set up in the kitchen or bathroom where the spouse& kids might be using a hair dryer in the shower or trying to wash the veggies in the sink with a mixer why not dump the GFCI outlet and install a real outlet
 I know they are required in some places but I hate those things almost as much as I disliked the ELCB's in Europe
I live so far outside of the box, when I die they will stretch my carcass over the coffin

dnix71

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Re: SunkCo 788+ battery welder
« Reply #7 on: August 09, 2014, 09:29:10 PM »
The ground fault was found and fixed. The power bars pivot on a pin just behind a hole cut in the circuit board. One of the c-clips retaining the pin was touching the circuit board. There is very little clearance in some places, so the maker added tape to insulate things. I tightened the board mounts and added a piece of electrical tape to keep the clip from touching and that stopped the shorts.

I have 3 circuits in my apt. The one by my desk has a GFCI that protects 2 outlets. That is the one I used first. The bathroom was tried second and it tripped that one. I have one unprotected circuit and one outlet on another not protected. i tried those and no majic smoke, but I trust my GFCI's so I went back inside and rechecked.

Still no battery charger working, though. The seller has contacted me and asked me to show him how to properly wire the machine for the US market and I explained that the green wire in the US is a redundant neutral. NEC says white cannot carry current and any other color is okay for hot. Also the fuse needs to be inline with the hot wire.

The original plug and cord had a green and red wire but was not polarized.

dnix71

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Re: SunkCo 788+ battery welder
« Reply #8 on: August 09, 2014, 10:07:36 PM »
Here is a pic of the short.


dnix71

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Re: SunkCo 788+ battery welder
« Reply #9 on: August 14, 2014, 04:28:21 PM »
The seller refunded me $20 after I complained about the non working battery charger.