788 spot welder

[Punx0r]

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.

If I understand this description correctly then my concern is that the ground (safety earth) would be carrying return current/voltage. As long as the earth system for the building is good that shouldn't be a problem, but if it were incomplete or had high impedance you could see dangerous voltages on earthed items like pipework or device casings.

It's something I might be tempted to do in my own home out of expediency as a temporary, one-off event.

 

[mfj197]

I have a 788+ which performed faultlessly welding up my 10S4P pack here in the UK (so on 240V). Nothing more to add really - didn't have any problems at all and it produced consistent, strong welds. Definitely dual pulse, and I put three welds on each joint so wasn't hanging about. I've no idea about welds per minute though.

Michael

 

[Syonyk]

Well, good to know they seem to work properly on 240v.

I suppose at some point here now that I've finished my pack rebuild, I'll stress it and see if the new triac location keeps things cooler. I might just have had an underwhelming triac to start with.

 

[Electric Junk]

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?

Full voltage.....Is there a better alternative?

 

[Syonyk]

I suppose I shouldn't even ask what the micro switch was rated for in terms of breaking inductive loads?

Generally, if you're going to do something like that, a low voltage (5v or 12v is common) signal is run to the micro switch, which is then used to drive a relay (or triac) that switches the actual mains current. Breaking inductive loads is hard, as the nature of the load will create a strong voltage spike (and often an arc across the contacts) when broken. Transformers are inductive loads, which usually derates a switch significantly as compared to a pure resistive load.

I'm not a fan of having my finger right up against 120v either. Just a personal preference.

 

[mlt34]

I have a 788, a 787A+ and a third cheap spot welder. I'm traveling right now but when I get back I intend to post up some pics and reviews comparing them.

 

[Syonyk]

^ That would be very, very useful!

I'm going to be getting my scope back soon and can start analyzing waveforms and how the 788+ controls interact with each other.

 

[dnmun]

that will help. watch the ground and you will see the spike that is killing your triac. then convert it to 240V and watch the ground then and see what happens to the spike on the ground.

 

[Syonyk]

I don't believe it's easy to convert the welder from 110v to 220v - there are no spare taps on the transformer that could be used, so I strongly suspect it's a different transformer entirely. It would be easier to just buy a 220v version of the welder, but right now, I don't have a way to power that, and I'm not going to rewire the place I'm renting.

 

[silentflight]

I have a 788, a 787A+ and a third cheap spot welder. I'm traveling right now but when I get back I intend to post up some pics and reviews comparing them.

Great- a trickle of information on these welders is becoming a flood!

Haven't seen much from the Australians and Kiwis on this yet- what are you guys using? Are some of you satisfied users of 220-240V units?

I'm going to be getting my scope back soon and can start analyzing waveforms and how the 788+ controls interact with each other.

I hope you will take us all along for the ride in gory detail... On the one hand, I want to see the tracings and understand the unit, on the other, I feel like you should benefit from the hard work rather than publish a guide for the manufacturer to make version 2.0 better.

I'd also like to see oscilloscope screen shots of the JP welder, not because I have any doubts about it, but simply to admire what one person can accomplish with modern electronics. It may also have some subtleties which riba and others can point out.

 

[riba2233]

I'd also like to see oscilloscope screen shots of the JP welder, not because I have any doubts about it, but simply to admire what one person can accomplish with modern electronics. It may also have some subtleties which riba and others can point out.

I'll do my best to make them after I come back from my trip

 

[Syonyk]

I hope you will take us all along for the ride in gory detail... On the one hand, I want to see the tracings and understand the unit, on the other, I feel like you should benefit from the hard work rather than publish a guide for the manufacturer to make version 2.0 better.

I'll see what I can do. My scope is quite ancient, and I still need to collect it back (I gave it to a guy who rebuilds old arcade machines, but he's since found a better scope). I can't promise anything amazing, but I do intend to spend some quality time figuring out how the damned thing works, and looking for things that can be improved.

I think it's entirely possible that a reliable, high weld frequency 110v version of these can be created, but it will require some modification and perhaps active cooling (a "fan").

I'm not that concerned about them using my information to make the product better. I don't see an easy way to profit from the information short of building and selling modified 110v versions, which seems like an awful lot of work for not that much money. If the end result is more people being able to reliably use well controlled welding currents on lithium batteries, that's fine with me.

 

[tomjasz]

I have a 788, a 787A+ and a third cheap spot welder. I'm traveling right now but when I get back I intend to post up some pics and reviews comparing them.

Welder riches!

 

[mlt34]

I have a 788, a 787A+ and a third cheap spot welder. I'm traveling right now but when I get back I intend to post up some pics and reviews comparing them.

Welder riches!

Well only one and a half are working right now, hence the welder zoo I've built :-/

 

[dameck]

Hello my name is Chris
and this is going to be my first post here.
Some days ago I received my 788+ spot welder from Aliexpress.
Yesterday I switched the spot welder on the first time and the house circuit breaker (B16) went off. (I have 220Vac - European standard)
So today I bought a C16 and also B20 circuit breaker and tried with them.
I have still the same issue.
I switch the welder on and the house circuit breaker is switching off immediatly.

FYI: The 20A fuse inside the welder is looking good.

Does anybody know about these kind of problem?

I would be very thankful for your support.

Thank you very much in advance!

Kind regards,

Chris

 

[Thornet]

Hello my name is Chris
and this is going to be my first post here.
Some days ago I received my 788+ spot welder from Aliexpress.
Yesterday I switched the spot welder on the first time and the house circuit breaker (B16) went off. (I have 220Vac - European standard)
So today I bought a C16 and also B20 circuit breaker and tried with them.
I have still the same issue.
I switch the welder on and the house circuit breaker is switching off immediatly.

FYI: The 20A fuse inside the welder is looking good.

Does anybody know about these kind of problem?

I would be very thankful for your support.

Thank you very much in advance!

Kind regards,

Chris

Hello Chris. I had this exact problem and I solved it by installing a resistor and a switch in paralell.

When I turn the welder on I limit the startcurrent through the resistor to about 5 A max. When I decide to do the welding I flip the switch so current goes through the switch instead.
I assume the newer circuit breakers don't tolerate a fast highpeak-current at startup which trips the breaker. Hope this helps.
I even use a C 20A breaker, and it can't handle the inrush current at startup...

 

[Syonyk]

The inrush current on these is certainly brutal. :/

 

[burningwings]

I recently obtained a 788 110 volt spot welder. Been testing it on flashlite batteries. I don't want to damage my 18650's . It works perfectly so far , hope it keeps it up.

 

[dameck]

Hello my name is Chris
and this is going to be my first post here.
Some days ago I received my 788+ spot welder from Aliexpress.
Yesterday I switched the spot welder on the first time and the house circuit breaker (B16) went off. (I have 220Vac - European standard)
So today I bought a C16 and also B20 circuit breaker and tried with them.
I have still the same issue.
I switch the welder on and the house circuit breaker is switching off immediatly.

FYI: The 20A fuse inside the welder is looking good.

Does anybody know about these kind of problem?

I would be very thankful for your support.

Thank you very much in advance!

Kind regards,

Chris

Hello Chris. I had this exact problem and I solved it by installing a resistor and a switch in paralell.

When I turn the welder on I limit the startcurrent through the resistor to about 5 A max. When I decide to do the welding I flip the switch so current goes through the switch instead.
I assume the newer circuit breakers don't tolerate a fast highpeak-current at startup which trips the breaker. Hope this helps.
I even use a C 20A breaker, and it can't handle the inrush current at startup...

Hello Thornet,

thanks a lot.
I will try this and leave my feedback after I am done.

Kind regards,

Chris

 

[dameck]

Hello my name is Chris
and this is going to be my first post here.
Some days ago I received my 788+ spot welder from Aliexpress.
Yesterday I switched the spot welder on the first time and the house circuit breaker (B16) went off. (I have 220Vac - European standard)
So today I bought a C16 and also B20 circuit breaker and tried with them.
I have still the same issue.
I switch the welder on and the house circuit breaker is switching off immediatly.

FYI: The 20A fuse inside the welder is looking good.

Does anybody know about these kind of problem?

I would be very thankful for your support.

Thank you very much in advance!

Kind regards,

Chris

Hello Chris. I had this exact problem and I solved it by installing a resistor and a switch in paralell.

When I turn the welder on I limit the startcurrent through the resistor to about 5 A max. When I decide to do the welding I flip the switch so current goes through the switch instead.
I assume the newer circuit breakers don't tolerate a fast highpeak-current at startup which trips the breaker. Hope this helps.
I even use a C 20A breaker, and it can't handle the inrush current at startup...

Hello Thornet,

yesterday I received a new circuit breaker.
I ordered a D-20A circuit breaker and suprisingly it is working fine : )
Today I did the first weldings and the result is good.
So now I can start to build up my battery pack.

Thanks a lot for your support.

Kind regards,

Chris

 

[999zip999]

Chris pic's please.

 

[maanebedotten]

I just recieved this welder in 220v version and have done some preliminary testing. I have no experience with welding though so I am a bit lost as to how to set it up for best results.

Every time I turn it on the 16a breaker goes, so the only way for me to turn it on is to reset the breaker while the unit is turned on. This is not optimal, but i dont think it is too unsafe considering that the inrush is so short duration. If i turn the digital setting up above 70 the breaker also goes so i did most of my testing at digital setting below 50.

I did some welds with the digital setting set to 10 and the dial set to both its minimum and maximum. My impression is that the pulse lasted longer with the dial turned all the way up. This leads me to think that the dial is for pulse length setting and the digital is for current setting.

I only have 0.15mm nickel so this is what I used for testing. I get what I consider good results with the digital set to 50 and the dial set to between 0.5 and 1. I have to use pliers to get the nickel back off, and there is a hole in the strip at the weld spots. Sometimes there is even a hole in the battery too.

Is this proof of a good weld or are there other indicators I can look at to determine weld quality?
What settings do you guys use with good results?

 

[Syonyk]

I did some welds with the digital setting set to 10 and the dial set to both its minimum and maximum. My impression is that the pulse lasted longer with the dial turned all the way up. This leads me to think that the dial is for pulse length setting and the digital is for current setting.

Certainly possible. I haven't taken my scope to it yet - no time for such things with all my other projects. I've been pretty conservative with mine due to having blown up the triac once already, and needing it for actual projects.

I only have 0.15mm nickel so this is what I used for testing. I get what I consider good results with the digital set to 50 and the dial set to between 0.5 and 1. I have to use pliers to get the nickel back off, and there is a hole in the strip at the weld spots. Sometimes there is even a hole in the battery too.

I think I've been welding around 70 on the digital display with the dial turned all the way down. Holes in the strip is good, holes in the battery is not good - you're dumping too much energy in if it's softening the battery case that much.

Is this proof of a good weld or are there other indicators I can look at to determine weld quality?

Generally, you want the welds to be strong, but not burned. Charred black on your strip is probably too much energy.

What settings do you guys use with good results?

70 2 with the dial at 0 for 0.15mm strip, 2-3 welds per terminal, and the terminal is only slightly warm to the touch after welding. Start with too little energy and ramp it up until you get good, solid welds, then don't go beyond that - dumping excess heat into the battery does nothing good.

 

[Punx0r]

Try a type-C circuit breaker - they all twice the surge of the type-B which is normally fitted. They're recommended for large motors/transformers and other loads with high in-rush current. Type D allows even more over-current, but may be excessive for what you need.

 

[Syonyk]

Try a type-C circuit breaker - they all twice the surge of the type-B which is normally fitted. They're recommended for large motors/transformers and other loads with high in-rush current. Type D allows even more over-current, but may be excessive for what you need.

Good advice - thanks! I know a lot of people have been having trouble with their breakers popping.