788 spot welder

Batteries, Chargers, and Battery Management Systems.
Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 17 2015 1:35am

burningwings wrote:Thanks sooo much Syonyk !!!
You're welcome. :) I appear to currently have the most public information of anyone on these things...

Take it easy with it, especially if you're on 110v, boost the pressure a bit if you're arcing (I'm 5-7 turns "increased" on welding pressure compared to where it ships, which is probably totally random), don't touch the SET CURRENT knob unless you figure out what it does, and have spare triacs and fuses.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

silentflight   100 W

100 W
Posts: 119
Joined: May 07 2007 5:42pm
Location: Chicago

Re: 788 spot welder

Post by silentflight » May 17 2015 1:51pm

WOW. Thanks, Syonyk. I feel like a thorough reading of your posts should qualify me for a certificate of Chinese Spot Welders to hang on my wall. Seriously good stuff.
Syonyk wrote:I didn't get the impression rebuilding a commercial ebike pack was that interesting to people here, though.
I hope you will share a link to your upcoming specific blog post(s) on rebuilding in a new thread in the battery section, no doubt it will be closely read by many on the Sphere. As for you getting the impression that a pack rebuild by a talented person might not be of interest on this forum... well, that's an unintended indictment of what should be the premier DIY ebike forum which we as a community should take to heart, let's get things back on track!
mcintyretj wrote:I decided to scrap all the electronics and just use a switch as shown in hundreds of youtube videos. Here is the welder today.
mcintyretj- I appreciate your post as well. It highlights the dire need for a safe and reliable spot welder at a reasonable price and has Macgyver written all over it.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 17 2015 2:30pm

silentflight wrote:WOW. Thanks, Syonyk. I feel like a thorough reading of your posts should qualify me for a certificate of Chinese Spot Welders to hang on my wall. Seriously good stuff.
It really shouldn't. I don't feel that I understand this specific welder at all yet. After I've had a chance to stick a scope on the various power regions, determine how the triac is triggered, determine how the digital settings and the current set knob interact to determine pulse width, and profile the current over time of the varying length pulse widths, I might say I understand this one particular welder decently, though I could still benefit from reverse engineering it (which, sadly, I'm not any good at yet).
I hope you will share a link to your upcoming specific blog post(s) on rebuilding in a new thread in the battery section, no doubt it will be closely read by many on the Sphere. As for you getting the impression that a pack rebuild by a talented person might not be of interest on this forum... well, that's an unintended indictment of what should be the premier DIY ebike forum which we as a community should take to heart, let's get things back on track!
I'll probably get around to linking it, but it's not a multi-kwh Hobby Lipo pack, and I didn't replace a perfectly well designed pack with Hobby Lipos, so... we'll see. I expect an awful lot of "Why did you waste your money doing that?" responses.

This is my first pack rebuild, so we'll see how it compares to others.
mcintyretj- I appreciate your post as well. It highlights the dire need for a safe and reliable spot welder at a reasonable price and has Macgyver written all over it.
Alternately, it indicates that a safe and reliable spot welder should cost more. I would happily have paid more for a better unit than my 788+ if there was anything between $200 and $2k...
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

dnmun   100 GW

100 GW
Posts: 16190
Joined: Jun 09 2008 1:32pm
Location: portland, or and loveland, co

Re: 788 spot welder

Post by dnmun » May 17 2015 3:42pm

i tried to repair one of those that someone had taken apart for some reason when it would not work. it ended up shorted out and blowing plasma out the front end because i had it on a 60A 240V circuit and the plasma was not enuff to blow the breaker. looked like roman candles shooting out through the opening in the front.

the pressure is the pressure at which the microswitch hits the contacts so that is the force exerted at the tips to make it shoot the pulse.

you should use these on 240V so you don't have as much trouble with the triac. if you don't have 240V then you can pull cable from the service panel in your house over to the location for the welder but use 240V to power it.

User avatar
tomjasz   1.21 GW

1.21 GW
Posts: 3842
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: 788 spot welder

Post by tomjasz » May 17 2015 4:12pm

I bought a Sunkko 709A. It worked for a few welds and a day. After I released the money on Aliexpress, a day later it promptly blew a fuse and the party is over.
I suggest if you buy one use the hell out of it before you release the payment. Once paid, all bets are off. Weeks of emails and they are sending a new PCB.
That is NOT an easy task. Sadly I have $250 worth of useless electronics. I think I'd have gone with the guy in Croatia and the batt powered if I had it to do again. Better yet, I should have stashed the cash and saved for a $1200 unit from a USA seller.

The most important lesson for me was understanding once payment is released you're at the mercy of someone in China. My battery reseller whose English is quite good tried to contact the seller of the welder to help me sort it but Elisa Zhao refused to answer her. Pooched.
Attachments
SUNKKO-709A-High-Power-Spot-Welder-Soldering-Station-with-Universal-welding-pen-1KG-Nickel.jpg
SUNKKO-709A-High-Power-Spot-Welder-Soldering-Station-with-Universal-welding-pen-1KG-Nickel.jpg (139.16 KiB) Viewed 1257 times
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 17 2015 4:43pm

If it just blew a fuse, why can't you simply replace the fuse? Or is "blew a fuse" a generic term for "something failed"?

If you have the circuit board out, could you take a couple high resolution photos of both sides of the board, and a few shots of the inside of the unit? I'd be interested to see what it's doing - that's a similar welder, but it's enough different that it would be interesting to compare.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

User avatar
tomjasz   1.21 GW

1.21 GW
Posts: 3842
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: 788 spot welder

Post by tomjasz » May 18 2015 12:31am

Blew the house circuit breaker. No sign of anything on one died of the pcb. Kinda looks like it was not designed to be fixed without some serious trouble, for this inexperienced user. I will take pictures soon and post.
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

meelis11   100 W

100 W
Posts: 116
Joined: Jul 30 2013 5:29am
Location: Tallinn, Estonia

Re: 788 spot welder

Post by meelis11 » May 18 2015 5:53am

I just received 788+ spotwelder lately and today got nickel tabs so I can start experimenting...
subscribing here

csheep   1 mW

1 mW
Posts: 12
Joined: Aug 01 2014 3:06pm

Re: 788 spot welder

Post by csheep » May 18 2015 6:08am

Hi,

A quick feedback about that line of spot welders... I bought a 709A a couple weeks ago which must not be very different from the 788. Product worked perfectly for my 18650 pack. I spot welded 0.15mm nickel tabs without a problem, I don't think 0.2mm strips would have been much more difficult. Seeing how I had to put 3 layers of nickel strips on top of each other on my whole pack, I must have done over a hundred welds without any difficulties.

I had to put the 709A on a 20A 220V power line. It could work on a 16A line but you have to take out all the other electrical equipements sharing the same power line.

The foot pedal to trigger the weld is great, much better than the "pressure" mechanism IMO.

Best regards,

CS

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 12:31pm

tomjasz wrote:Blew the house circuit breaker. No sign of anything on one died of the pcb. Kinda looks like it was not designed to be fixed without some serious trouble, for this inexperienced user. I will take pictures soon and post.
Did the fuse in the welder fail or was it bypassed?
meelis11 wrote:I just received 788+ spotwelder lately and today got nickel tabs so I can start experimenting...
subscribing here
If it's the 110 version, take it slow and it should be fine. If 220, you can probably go at it hard without issues, from what people seem to be saying.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

dnmun   100 GW

100 GW
Posts: 16190
Joined: Jun 09 2008 1:32pm
Location: portland, or and loveland, co

Re: 788 spot welder

Post by dnmun » May 18 2015 2:42pm

if you already have the 120V version then see what you need to do in order to power it off of the 240V AC. the manufacturer may be able to help by showing a diagram of which transformer leads to change and where to wire it up.

if you do not have 240V then it is available at the service panel and if you have wiring currently into the room where the work is done then you could convert the 120V service in that room over to 240V using the cables already in the wall.

this allows you to use the current 12-2 w/g for your 240V power to that room but it would require taking out all the duplex outlets on the leg serving that room and converting them to handle the two 120V phases on each of the duplex plugs.

it is really simple because the duplex outlet has a copper jumper connector on the outside of the plug that connects the two hot legs together. take some pliers and grab the edge of that jumper and twist it back and forth to break off the jumper so that the two outlets are isolated on the hot side, but connected on the ground side. you do not break the jumper on the ground side.

then use the bare copper wire ground as the common for each of them by connecting that bare ground to the ground side of the plugs and then on the other screw available on the grounded or common side of the plug run a short bare wire down to the ground screw at the bottom of the duplex outlet and then you will have a ground for each of the two 120V AC plugs.

but for the plug you use to make the 240V then leave the jumper intact so that both the plugs are available at 240V. on this duplex outlet you would put the white wire on the regular common side and your ground would remain separated and on the ground screw only so that there is 240V across the duplex outlet.

then go to the service panel and find that wire which you already had turned off the breaker. find the white ground/common wire that runs over to the ground and remove it from the ground bar and attach it to the breaker adjacent to the one you use for the service that was converted. the adjacent breaker is the other phase of the 240 so now you will have a 240V duplex service in the room where you use the spot welder. and use a regular cord for the 240V power.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 4:19pm

Ground is not designed to be used as a neutral, as I understand normal household wiring.

In addition to having a 110v plug compatible 240v outlet being a fire waiting to happen.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

dnmun   100 GW

100 GW
Posts: 16190
Joined: Jun 09 2008 1:32pm
Location: portland, or and loveland, co

Re: 788 spot welder

Post by dnmun » May 18 2015 4:21pm

no it is not. you just don't know. 240V w/g is a common power source in most countries around the world.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 4:30pm

And it's not in the US.

Not everything with a 110v style plug (two parallel vertical blades and a ground) can handle 240v.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

dnmun   100 GW

100 GW
Posts: 16190
Joined: Jun 09 2008 1:32pm
Location: portland, or and loveland, co

Re: 788 spot welder

Post by dnmun » May 18 2015 5:09pm

it is in the US because i have done it in three different houses that i own and it works better than the regular wiring because it doubles the load bearing capacity of the already installed house wiring. like i said, you just don't know and don't do stuff either or you would understand.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 5:42pm

I generally don't go rewiring rental houses to provide 240v in what everyone else will assume is a standard outlet - that's not a habit I've gotten into, and not one I intend to get into. In this particular case, I'm fine with relocating the triac and welding slower.

If I understand your modification properly, you're taking a standard two wire (hot, neutral) plus ground setup into a room, replacing the neutral with an out of phase hot (for a 240v difference between them), modifying the other outlets to use the ground as their new neutral, and then tying the ground to that neutral. You've now made the existing ground the neutral, and there is no proper ground anymore.

I don't argue that it works, in terms of providing proper voltages at the outlets. I understand that it works.

I'm arguing that it's not a good idea (actually, I think it's a truly terrible idea), partly because you have a 240v outlet that a 110v device can be plugged into (not everything with a plug is an auto ranging switching power supply), and partly because you're consistently dumping line voltage into a ground wire instead of a protected neutral wire, and this can lead to significant potentials on exposed metal if everything isn't perfect.

"Doubling the load capacity of already installed wiring" is not a good idea either. It's spec'd out to a certain gauge and design for valid reasons, and your modification tosses those all out the window.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

User avatar
tomjasz   1.21 GW

1.21 GW
Posts: 3842
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: 788 spot welder

Post by tomjasz » May 18 2015 6:04pm

silentflight wrote:I hope you will share a link to your upcoming specific blog post(s) on rebuilding in a new thread in the battery section, no doubt it will be closely read by many on the Sphere. .
Absolutely. I am going to start a post on my saga too. A sad tail but a chance to learn.
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

User avatar
tomjasz   1.21 GW

1.21 GW
Posts: 3842
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: 788 spot welder

Post by tomjasz » May 18 2015 6:09pm

Syonyk wrote:
tomjasz wrote:Blew the house circuit breaker. No sign of anything on one died of the pcb. Kinda looks like it was not designed to be fixed without some serious trouble, for this inexperienced user. I will take pictures soon and post.
Did the fuse in the welder fail or was it bypassed?
Fuse in the welder is good.
Attachments
IMG_1158.jpg
Parts is parts.
IMG_1158.jpg (149.17 KiB) Viewed 4639 times
IMG_1174.jpg
IMG_1174.jpg (104.88 KiB) Viewed 4639 times
IMG_1173.jpg
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

Electric Junk   10 W

10 W
Posts: 93
Joined: May 13 2013 5:20pm
Location: NJ

Re: 788 spot welder

Post by Electric Junk » May 18 2015 7:45pm

I was looking at the chinese welder but eventually decided make a mot welder. Works fantastic. I would never go back to soldering cells. I tried it a few times but didn't feel safe doing it because i had a few start to smell. Welding cells is a game changer.

burningwings   100 mW

100 mW
Posts: 37
Joined: May 03 2015 11:39pm

Re: 788 spot welder

Post by burningwings » May 18 2015 10:18pm

Quick change triac ! Good idea !!!!

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 10:34pm

tomjasz wrote:Fuse in the welder is good.
Interesting. Have you tried replacing the triac in there (the three legged gizmo hanging loose on wires)? They can fail in interesting ways. It'd be my first step.

I'm surprised that the fuse in the unit is good if it blew the circuit breaker, though. Are there a lot of other things on the circuit?
Electric Junk wrote:I was looking at the chinese welder but eventually decided make a mot welder. Works fantastic. I would never go back to soldering cells. I tried it a few times but didn't feel safe doing it because i had a few start to smell. Welding cells is a game changer.
What are you using to control the current pulse?
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

User avatar
tomjasz   1.21 GW

1.21 GW
Posts: 3842
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: 788 spot welder

Post by tomjasz » May 18 2015 10:47pm

Syonyk wrote:
tomjasz wrote:Fuse in the welder is good.
Interesting. Have you tried replacing the triac in there (the three legged gizmo hanging loose on wires)? They can fail in interesting ways. It'd be my first step.

I'm surprised that the fuse in the unit is good if it blew the circuit breaker, though. Are there a lot of other things on the circuit?
No I used a circuit with nothing else on it. Sadly I'm a beginner at soldering. I guess I'll put it on the back burner until I can get some confidence in soldering.

Nothing seems, from what I can see, dis colored or split.
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 18 2015 11:00pm

It could still be bad. But that's harder to test.
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

Electric Junk   10 W

10 W
Posts: 93
Joined: May 13 2013 5:20pm
Location: NJ

Re: 788 spot welder

Post by Electric Junk » May 19 2015 12:48am

Syonyk wrote:
tomjasz wrote:Fuse in the welder is good.

What are you using to control the current pulse?
I use a micro switch on the electrode tip and hold it like a pencil and press the lever with my index finger. No issues with the switch even though i wondered how it could handle the cycles.

Syonyk   10 kW

10 kW
Posts: 517
Joined: May 16 2015 12:41am

Re: 788 spot welder

Post by Syonyk » May 19 2015 12:51am

Were you running a low voltage signal to the micro switch and driving the transformer with a relay, or were you running full line voltage through the microswitch?
Battery packs, Sunkko Welders, and more. http://syonyk.blogspot.com/

Post Reply