DIY spot-welder, FET-switched, processor-timed adj. pulse

Batteries, Chargers, and Battery Management Systems.
Post Reply
okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

DIY spot-welder, FET-switched, processor-timed adj. pulse

Post by okashira » Feb 03 2016 1:12pm

[this post is labeled as being from "okashira", but I have split this topic into its own thread with approval from Riba, and taken over this post in order for the first post to reflect this threads' mission and content. The okashira content was merged into the next post, -spinningmagnets]

ES member riba2233 (from Croatia) was selling a low-voltage/high current spot welder, and also selling less-expensive kits for customers who want to save money by doing the assembly themselves. Due to health and family concerns, he is no longer selling them.

"JP spot welder"
https://endless-sphere.com/forums/viewt ... 31&t=68865

riba2233's "sales thread" has devolved into a scramble to find ways to copy this type of DIY spot-welder, so I am splitting this off into its own thread in the battery section.

Since nickel strips are in physical contact with the 18650 cell-ends, high voltage is not necessary. 12V automobile starter batteries are common, and are already capable of high temporary currents. What makes this style of spot-welder interesting is the feature-set it provides compared to common industrial desk-top spot-welders, which typically need a high-amp power supply to load a large capacitor bank. Common wall-sockets in homes are sometimes overloaded by the demands, which customers may not find out until after they have purchased a spot-welder.

Since the voltage does not need to be high, some builders are enjoying satisfactory results using lithium batteries for the current using 2S and 3S packs, with recycled 18650's or LiPo (8V, 12V).

When dealing with high-amp DC, the on/off switch can experience arc-ing, and in a worst-case scenario, the contacts can be welded together themselves. With no way to turn the DC device off, it can lead to a spectacular melt-down. This style of spot-welder uses MOSFET electronic on/off switches, which are common inside high-powered ebike controllers.

The length of time that the current is "ON" is vital to control in order to achieve consistent results. It should be long enough to make a solid connection, but not so long that excessive heat is built-up and damages the internal cell chemicals. The length of time that current is flowing is called the "pulse", and it is measured in one-thousandths of a second, called milli-seconds. Thicker metal bus-strips need a longer pulse, thinner strips need a shorter pulse. This device uses a programmable microprocessor to adjust the pulse-width.

Content in this post from below this line is from ES member okashira:

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
The welder works fine as-is. You can weld up to 0.2mm nickel easily with the kit supplied by Riba using a lead acid starter battery. You can even weld 0.3mm nickel, but be mindful that the mosfets stay as cool as possible and don't use too powerful of a battery.

The diode is an upgrade for those of us that want 2000 amps and longer welding leads and want to weld lots and lots of 0.3mm nickel. Just use a lead acid starter battery. Don't worry about amps, S, P, whatever, just use a battery like Riba recommends and it will be fine. You can probably use the one from your car.

This is the BEST 18650 spot welder you can buy for under $2,000. Period. Your next option is a Sunstone Engineering welder. This one can work just as well.
Last edited by okashira on Feb 03 2016 3:50pm, edited 1 time in total.
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 03 2016 1:14pm

It really took me a while to figure this out, but I finally figured out how to fix the problem when using the welder at higher currents with longer welding leads.
I have blown over 100 mosfets so I got tired of it...

You can attach a high current diode like shown in black:
Image
The black wires should be as short as possible to minimize inductance. Now the inductance of the welding leads can be high and not cause anymore mosfet failures.

Since I have a bunch of this awesome aerospace grade 4awg silicone wire, I might offer a high end welding packing upgrade for riba's welder - longer super flexible leads/electrodes + diode

One side of diode gets attached to JP welder "welding lead" side.
Other side to battery positive terminal.
Diode points in direction of battery.
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

999zip999   100 GW

100 GW
Posts: 8309
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: JP spot welder

Post by 999zip999 » Feb 03 2016 1:55pm

It sounds like the concussion after an explosion. As vacuum.

User avatar
Offroader   10 MW

10 MW
Posts: 2122
Joined: Sep 08 2013 9:03pm
Location: USA

Re: JP spot welder

Post by Offroader » Feb 03 2016 3:15pm

okashira wrote:It really took me a while to figure this out, but I finally figured out how to fix the problem when using the welder at higher currents with longer welding leads.
I have blown over 100 mosfets so I got tired of it...

You can attach a high current diode like shown in black:
Image
The black wires should be as short as possible to minimize inductance. Now the inductance of the welding leads can be high and not cause anymore mosfet failures.

Since I have a bunch of this awesome aerospace grade 4awg silicone wire, I might offer a high end welding packing upgrade for riba's welder - longer super flexible leads/electrodes + diode

Can we get some more details on this? I may have to increase my current because I want to weld .3 nickel. If placing a simple diode will help me increase my current without blowing my fets then I will do this.

Just need more information about this and if it really works? How much current can you now safely use with this? Like can I use 1400 cranking amps instead of the 1100 limit set by riba?

Pictures of a completed setup and part number for a suitable diode will also be nice.

Thanks

NetPro   10 mW

10 mW
Posts: 20
Joined: Oct 09 2015 2:52pm
Location: USA

Re: JP spot welder

Post by NetPro » Feb 03 2016 3:22pm

Offroader wrote:
Can we get some more details on this? I may have to increase my current because I want to weld .3 nickel. If placing a simple diode will help me increase my current without blowing my fets then I will do this.

Just need more information about this and if it really works? How much current can you now safely use with this? Like can I use 1400 cranking amps instead of the 1100 limit set by riba?

Pictures of a completed setup and part number for a suitable diode will also be nice.

Thanks
Same here. Would like to be able to see the original pic posted but it is no longer on the ES server.

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 03 2016 3:52pm

Fixed the pic.
I'm using about 2000+ amps but only get a few hundred welds before FET's blow
This diode should work fine: http://www.mouser.com/Search/ProductDet ... SA300I45NA
Mine will come in tomorrow and i'll hook it up and post pics/results.
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 03 2016 4:12pm

Offroader wrote:
okashira wrote:It really took me a while to figure this out, but I finally figured out how to fix the problem when using the welder at higher currents with longer welding leads.
I have blown over 100 mosfets so I got tired of it...

You can attach a high current diode like shown in black:
Image
The black wires should be as short as possible to minimize inductance. Now the inductance of the welding leads can be high and not cause anymore mosfet failures.

Since I have a bunch of this awesome aerospace grade 4awg silicone wire, I might offer a high end welding packing upgrade for riba's welder - longer super flexible leads/electrodes + diode

Can we get some more details on this? I may have to increase my current because I want to weld .3 nickel. If placing a simple diode will help me increase my current without blowing my fets then I will do this.

Just need more information about this and if it really works? How much current can you now safely use with this? Like can I use 1400 cranking amps instead of the 1100 limit set by riba?

Pictures of a completed setup and part number for a suitable diode will also be nice.

Thanks
The FET's are only rated for an avalanche current of 150A peak. That puts welder current as designed to 900A peak, because you can expect full current of the pulse to flow thorough the mosfets when they're turned off. (inductance sucks) even if it's for100uS.

The Diode circuit gives the current somewhere to go once the FET's are opened... no more avalanche current. Of course there is inductance in the diode diode, but it's much smaller then the 4-6 feet of welding leads.

I was so focused on SOA curves when I was helping pick MOSFET's, I finally realized it's the avalanche current after turn off that kills them. That's why when we tried higher voltage MOSFET's they would blow even faster. Because the avalanche power = Vdsrated*I. You want as low voltage MOSFET as possible
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

User avatar
fechter   100 GW

100 GW
Posts: 12766
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: JP spot welder

Post by fechter » Feb 03 2016 8:07pm

okashira wrote:One side of diode gets attached to JP welder "welding lead" side.
Other side to battery positive terminal.
Diode points in direction of battery.
I think that's a good idea. I've thought about that too.

You could use a couple of FETs for the diode. Just tie gate to source and use the body diode.
The body diodes in the FETs used in the welder can handle pretty high currents for a short pulse.
"One test is worth a thousand opinions"

User avatar
riba2233   1 MW

1 MW
Posts: 1805
Joined: Jun 30 2013 10:23am
Location: Croatia

Re: JP spot welder

Post by riba2233 » Feb 04 2016 4:44am

Yeah that would be useful for people who want to use longer or thicker cables and higher currents than usual.

@netpro - yeah, it's mostly magic :lol: JK, I'm really glad that you are satisfied! :)

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 04 2016 11:22pm

I got the diode hooked up and It seems to be working.
Been running at max power (20ms) welding 0.3mm nickel like a champ in rapid succession. I have a special firmware with a 600ms delay so I'm welding FAST.
Even welded some nickel right to the Model S Aluminum bus bar. Pulling the nickel off pulls a layer of aluminum right off the bus bar. I was bypassing one of the leads, and the one welding lead was jumping like CRAZY. I'm guessing 3000+ amps.
Here is the setup:
Image
All connections are cleaned with a wire brush and clamped to hell, tested them at about 20 micro ohm.
The diode wire is way longer then needed, but still way shorter then my welding leads. The mosfets are getting noticeably less warm. I can weld at max power in rapid succession and they just get luke warm.
I'll shorten the diode wire later. Running about 8.15V, I will go ahead and push it to 8.3, then go with an A123 pack at 3s = 9.9V.
Attachments
welder diode.JPG
welder diode.JPG (248.35 KiB) Viewed 883 times
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

markz   100 GW

100 GW
Posts: 6091
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: JP spot welder

Post by markz » Feb 05 2016 2:24am

.
Last edited by markz on Feb 07 2016 11:29pm, edited 5 times in total.

User avatar
riba2233   1 MW

1 MW
Posts: 1805
Joined: Jun 30 2013 10:23am
Location: Croatia

Re: JP spot welder

Post by riba2233 » Feb 05 2016 7:08am

Looks good and easy to install :)

tomjasz   1.21 GW

1.21 GW
Posts: 3803
Joined: Mar 29 2014 1:45pm
Location: Out riding, MN USA
Contact:

Re: JP spot welder

Post by tomjasz » Feb 06 2016 1:17am

riba2233 wrote:I would rather spend time developing my weldless cases idea :)
YES! Please!
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.

ecycler   10 kW

10 kW
Posts: 800
Joined: Apr 03 2014 9:30pm
Location: USA

Re: JP spot welder

Post by ecycler » Feb 06 2016 2:11am

okashira wrote:Fixed the pic.
I'm using about 2000+ amps but only get a few hundred welds before FET's blow
This diode should work fine: http://www.mouser.com/Search/ProductDet ... SA300I45NA
Mine will come in tomorrow and i'll hook it up and post pics/results.
Is that diode getting hot at all when you push it hard? If not I may try a smaller schottkey I already have on hand...
Any grease is better than no grease.
The best exercises are the ones you enjoy doing.
I strongly prefer vehicles without doors.

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 06 2016 12:01pm

markz wrote:jibberish
OMG, really? Just remove your post. you are going to confuse people. I an well aware of the physics of electromagnetism the way you changed the diagram is WRONG
Even in electrical engineering they use what you call "laymen's" current flow. Look at a a diode symbol.
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

User avatar
Offroader   10 MW

10 MW
Posts: 2122
Joined: Sep 08 2013 9:03pm
Location: USA

Re: JP spot welder

Post by Offroader » Feb 06 2016 4:01pm

I found this video good in explaining why circuits are designed with conventional flow, which isn't the same as electron flow. Really, best to forget about the whole electron flow because it will just confuse you.

This video he explains why we still use the conventional current, basically because we always used it that way and it isn't actually wrong to look at it that way.


User avatar
fechter   100 GW

100 GW
Posts: 12766
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: JP spot welder

Post by fechter » Feb 06 2016 5:40pm

ecycler wrote:
okashira wrote:Fixed the pic.
I'm using about 2000+ amps but only get a few hundred welds before FET's blow
This diode should work fine: http://www.mouser.com/Search/ProductDet ... SA300I45NA
Mine will come in tomorrow and i'll hook it up and post pics/results.
Is that diode getting hot at all when you push it hard? If not I may try a smaller schottkey I already have on hand...
A smaller diode might work, depending on how much inductance there is. If the diode blows, it could be a problem though. It might be worth placing a fusible link in series with the diode. It will be pretty obvious if that blows.
"One test is worth a thousand opinions"

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 06 2016 9:25pm

ecycler wrote:
okashira wrote:Fixed the pic.
I'm using about 2000+ amps but only get a few hundred welds before FET's blow
This diode should work fine: http://www.mouser.com/Search/ProductDet ... SA300I45NA
Mine will come in tomorrow and i'll hook it up and post pics/results.
Is that diode getting hot at all when you push it hard? If not I may try a smaller schottkey I already have on hand...
No it doesn't get hot. Barely warmer then room temp. Smaller might be OK. I'll test current when I get my oscilloscope next week
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

User avatar
Offroader   10 MW

10 MW
Posts: 2122
Joined: Sep 08 2013 9:03pm
Location: USA

Re: JP spot welder

Post by Offroader » Feb 07 2016 2:26am

okashira, how thick does the two wires need to be that attaches to the diode?

Can this wire can be thinner than the welding lead wire?

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 07 2016 2:39pm

Offroader wrote:okashira, how thick does the two wires need to be that attaches to the diode?

Can this wire can be thinner than the welding lead wire?
Yes, esp if short, 8 even 10 awg would be okay
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

markz   100 GW

100 GW
Posts: 6091
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: JP spot welder

Post by markz » Feb 07 2016 11:28pm

Ok I will delete it,
In general, high school Physics and two year technician programs use Electron Flow.
But three year technologist and university engineering programs use Conventional Current.
You must realize what convention is being used because the rules change. Ex. Right-Hand rules in Conventional Current become Left-Hand rules in Electron Flow.
Many textbooks are available in both formats.

The battery negative terminal the short line, and positive terminal the long line.
From there, you either use conv. or elec. flow.
Hence, Cathode is negative Anode is positive.
So your + is on the negative terminal of EMF, as well on the Cathode negative of diode.
But we are using conventional flow though! :wink:

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 08 2016 12:13am

markz wrote:Ok I will delete it,
In general, high school Physics and two year technician programs use Electron Flow.
But three year technologist and university engineering programs use Conventional Current.
You must realize what convention is being used because the rules change. Ex. Right-Hand rules in Conventional Current become Left-Hand rules in Electron Flow.
Many textbooks are available in both formats.

The battery negative terminal the short line, and positive terminal the long line.
From there, you either use conv. or elec. flow.
Hence, Cathode is negative Anode is positive.
So your + is on the negative terminal of EMF, as well on the Cathode negative of diode.
But we are using conventional flow though! :wink:
Yes I drew the voltage source symbol backwards :)
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

User avatar
hagerty1   100 mW

100 mW
Posts: 35
Joined: Nov 04 2014 6:12am

Re: JP spot welder

Post by hagerty1 » Feb 08 2016 5:23pm

Ok I just got my fully assembled welder in today. Being a welder of many other materials I did not even think to look at what it took to run this thing.... 900+ amps @ 12VDC seems to be it. Jesus I can weld 1/2" steel plate with 900 amps. In any event, I made the mistake of not checking this out before buying it. But now that it is here...... I am reading about people blowing Fets left and right etc. I have no desire to blow this thing up. I assume everyone is welding using 12VDC for a reason.
I have followed the thread but I am still not sure if I can run the welder "as is" without diode fixes etc.
I have plenty of spare cells to build a pack to supply it. Can some one advise an S/P combination that will give me around 100 welds between charges. My cells are Panasonic CGR18650DA. I have plenty. Is 3S at 9-12.6V the magic # for voltage? What is the voltage tolerance of the welder? Can it take a 4S @ 12-15.6V ? My cells are supposed to be ok at 2C constant and up to 4-5C pulse. The cells are 2400 mAh. So I am thinking in pulse I could use 10 amps per cell as a calculator without kicking the cells ass. If I need 900 amps that is 3S 90P ?? As I don't know voltage tolerances I'm not sure. I have the 270++ cells as spares/ experimenters/ etc. anyhow. I assume it can take high voltages if it can run on a fully charged lead acid 12 volt. I would guess everyone will tell me to just go buy a car battery and have at it.....?????
If this is going to be an ultra pain in my rear I would rather just sell it and do something else......as of now it is un used and in the USA Ohio
Rolliing Sytems since 1992
Since light travels faster than sound,
some people appear bright until you hear them speak.

okashira   10 kW

10 kW
Posts: 955
Joined: Nov 17 2014 6:45pm
Location: Houston, TX

Re: JP spot welder

Post by okashira » Feb 08 2016 5:40pm

hagerty1 wrote:Ok I just got my fully assembled welder in today. Being a welder of many other materials I did not even think to look at what it took to run this thing.... 900+ amps @ 12VDC seems to be it. Jesus I can weld 1/2" steel plate with 900 amps. In any event, I made the mistake of not checking this out before buying it. But now that it is here...... I am reading about people blowing Fets left and right etc. I have no desire to blow this thing up. I assume everyone is welding using 12VDC for a reason.
I have followed the thread but I am still not sure if I can run the welder "as is" without diode fixes etc.
I have plenty of spare cells to build a pack to supply it. Can some one advise an S/P combination that will give me around 100 welds between charges. My cells are Panasonic CGR18650DA. I have plenty. Is 3S at 9-12.6V the magic # for voltage? What is the voltage tolerance of the welder? Can it take a 4S @ 12-15.6V ? My cells are supposed to be ok at 2C constant and up to 4-5C pulse. The cells are 2400 mAh. So I am thinking in pulse I could use 10 amps per cell as a calculator without kicking the cells ass. If I need 900 amps that is 3S 90P ?? As I don't know voltage tolerances I'm not sure. I have the 270++ cells as spares/ experimenters/ etc. anyhow. I assume it can take high voltages if it can run on a fully charged lead acid 12 volt. I would guess everyone will tell me to just go buy a car battery and have at it.....?????
If this is going to be an ultra pain in my rear I would rather just sell it and do something else......as of now it is un used and in the USA Ohio
Yes, I am sorry, don't want to mis lead people.
The welder works fine as-is. You can weld up to 0.2mm nickel easily with the kit supplied by Riba using a lead acid starter battery
You can even weld 0.3mm nickel, but be mindful that the mosfets stay as cool as possible and don't use too powerful of a battery.

The diode is an upgrade for those of us that want 2000 amps and longer welding leads and want to weld lots and lots of 0.3mm nickel.


Just use a lead acid starter battery. Don't worry about amps, S, P, whatever, just use a battery like Riba recommends and it will be fine. You can prob use the one from your car.

This is the BEST 18650 spot welder you can buy for under $2,000. Period. Your next option is a Sunstone Engineering welder. This one can work just as well.
"Peace out - I'm done."
-- Bernhard Riemann, 1859

edisonmotors.net
Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

User avatar
riba2233   1 MW

1 MW
Posts: 1805
Joined: Jun 30 2013 10:23am
Location: Croatia

Re: JP spot welder

Post by riba2233 » Feb 08 2016 5:49pm

Hi, Hagerty, I must tell you that you wont be lucky with using those cells as welding source unfortunately. It would be best to find a small car starting battery, that would be easiest, and least time consuming, and would work no problems. If you need any other advice please ask! It's simpler than it looks :) And BTW listen to okashira, he's right and has a lot of experience :)

Post Reply