Spot Welding Battery Packs

[crossbreak]

it is not a good idea to solder both wires exits to the same side like shown in this picture. The one FET closes to both source and sink will be loaded more than the others and will burn eventually.
Better solder the inut to one side of the FET bank and the exit to the other like I did show on top of this thread. This way all FETs are loaded equally.

 

[crossbreak]

btw i did weld again today a 10s5p pack. The setup posted on top of this thread is still my final one as it works fine so i wont change anything anymore.

I still use the two car batteries even if i weld thin nickel like 0.15mm. Just do shorter weld times like 1.2ms for the second pulse

BTW I still use dual pulse. Single pulse does not work good. Triple pulse does not work well too...makes more heat at the cell but does not enhance quality of the weld.

 

[riba2233]

So what are your final times for first and second pulse?

Should I use 1k resistor for every mosfet gate (or some other value)? How about 10k pulldown gate resistor, aslo one per fet or one for all fets?

Also, do you know why do we have to use such big value for gate resistor? (1k is kind of large gate resistance)

Thanks!

 

[\/ampa]

Hello all,


I have lurked since some time and have build this Spot Welding machine but have used 2x3s 20Ah A123 cells and 8x MOSFETs. I welded several hundred cells already and the MOSFETs highest temperature was little over 40°C. The cables are 25mm² OFC copper and about 60cm long. The electrodes are made of 5mm hard copper and even this short they get very hot after 50 fast weld´s.
The welds in the last picture are made with 0.3mm nickel strip. Its super strong. The sparks fly upwards. While welding i have to wear protective glasses.


View attachment 2

 

[arkmundi]

Thanks. I'm going to follow your path to a DIY spot welder before I attempt my next battery build.

 

[riba2233]

http://i.imgur.com/PLDPieL.jpg

http://i.imgur.com/7RdTgKi.jpg


Finally, nice welds, after some melting copper and destroyed mosfets

Final setting are:

4 x IRF1405 (5 mohm rdson)

First pulse - 1.2 ms
Delay - 100 ms
Second pulse - 3 ms
Energy source - new starter battery 45 Ah

It works excellent with 0.1 mm nickel tape. I don't ave thicker one, but I would just have to add more mosfets, or use ones with lower rdson, or use longer pulses.
Each mosfet has it's own 82 ohm gate resistor.

 

[cal3thousand]

http://i.imgur.com/PLDPieL.jpg

http://i.imgur.com/7RdTgKi.jpg


Finally, nice welds, after some melting copper and destroyed mosfets

Final setting are:

4 x IRF1405 (5 mohm rdson)

First pulse - 1.2 ms
Delay - 100 ms
Second pulse - 3 ms
Energy source - new starter battery 45 Ah

It works excellent with 0.1 mm nickel tape. I don't ave thicker one, but I would just have to add more mosfets, or use ones with lower rdson, or use longer pulses.
Each mosfet has it's own 82 ohm gate resistor.

I have a bunch of IRFB4110PbF lying around (rdson 4.5 mOhm), Would putting 5 or 6 of these do well enough for .15mm tape?

And you any of you think an old recovered AGM battery would work? (what I have available) .... Or should I go the Cap and supply route?

 

[\/ampa]

http://i.imgur.com/PLDPieL.jpg

http://i.imgur.com/7RdTgKi.jpg


Finally, nice welds, after some melting copper and destroyed mosfets

Final setting are:

4 x IRF1405 (5 mohm rdson)

First pulse - 1.2 ms
Delay - 100 ms
Second pulse - 3 ms
Energy source - new starter battery 45 Ah

It works excellent with 0.1 mm nickel tape. I don't ave thicker one, but I would just have to add more mosfets, or use ones with lower rdson, or use longer pulses.
Each mosfet has it's own 82 ohm gate resistor.

I have a bunch of IRFB4110PbF lying around (rdson 4.5 mOhm), Would putting 5 or 6 of these do well enough for .15mm tape?

And you any of you think an old recovered AGM battery would work? (what I have available) .... Or should I go the Cap and supply route?

IRFB4110 have compared to the IRF1324 3x higher rdson and and 2 time lower current rating.
I doubt it can work. Maybe if u put >12pcs IRFB4110 in parallel.

 

[riba2233]

Well it obviously works for me, and I'm using 4x 5mohm mosfets. But only for 0.1 mm tape. However, with 6 mosfets, a bit longer pulse, and good power source, I think it would work.

 

[crossbreak]

I use 110ah 12V starter battery, so my weld times are shorter.

For 0.15mm nickel, i use 300µs for the first and 1200µs for the second pulse, with 10ms delay between them.
For 0.30mm nickel i use 500µs for the first and 4200µs for the second pulse, with 10ms delay between them.

never tried 0.1mm tape since this will have to much resistance for my taste.

Nice to see the same gate resistor value that worked for me, does work for you as well. 100 Ohm does the job, too. I have a a single 10 kOhm pull down resistor at the Gate Driver output (if i remember right)... just to be sure.

 

[riba2233]

My spot welder built on proto-board is doing fine, but I wanted to make another one. I designed and ordered some pro PCB's, and today I've put the whole thing together and tested. This time I used irfb7440 mosfets, 2 ohm rdson and around 4600 pf gate capitance. I run first test with three mosfets, and the welds weren't good, just shooting through the nickel. After few tries I burnt mosfets, and one of them broke in half and flew into the air :lol:

I'm a little bit frustrated since my first board works fine, and the second doesn't eve though it's the same schematic. I should try with irf1404 tomorrow...

Here are the pics:

 

[crossbreak]

really nice try, but for decent weld even with thin 0,15mm nickel you'll need some more/and better fets...enough space there is on your pcb. so...
dont waste some 5€ for cheap fets but spend 25€ and be shure it does the job. How tiny are the cells you wanna weld? 0,1mm nickel? that doens't do anything if it is eventually narow.. better do the job once but do it nice..25€ is a lot less than i have spend on puffed chinese lipo cells lol

 

[riba2233]

Look, I already have a working version using only 4 pieces of irf1405 which are 5 mohm, and that's works fine for me. So that's not the problem, and money is also not a problem, I have more of these irfb7440, but I wanted to see if it will work with just three pieces.

 

[crossbreak]

the irfb7440 really looks promising, hope you get it working right with 6 in the end. I am a quite impatient an do a lot of welds quick. I am a bit affraid that FETs get too hot though. Maybe 6 of the irfb7440 could do quick welds (i do 1 per second) when using a heat sink. Do you plan to sell some of your PCBs? Do you have a timer circuit for first and second pulse (like an Attiny25??) on your board or just the drivers?

 

[riba2233]

I use PIC and I can program pulse times, but not on the fly. I could make boards for sell but first I want to make sure that everything is fine, I might have to do some minor changes. I chose 7440 because it's not expensive, it has low rds-on, but it also has low gate capitance.

 

[crossbreak]

cool indeed! looking forward to your progress. An LCD that shows weld pulse duration was something i always wanted. For me it is so easy to simply upload different timings and I almost always use the same nickel...so there is very little impulse to really do it. Still if i'd sell this stuff i would think about that. A 1602 lcd can be bought for about 1€. Two buttons aren't expensive too. A nice alloy housing would make it a really sophisticated product for which you could charge some real money

 

[riba2233]

Yep, I'm aware of that This is still alpha version, but I'll implement some sort of display and changing pulse times on the fly in the future.

Some news: I've just replaced mosfets, installed 4 pieces of irf1404 next to each other and it works! It works just like mine old spot welder, it's fine for 0.1 mm nickel. I'm going to build another one with stronger mosfets on another board so I can see how's that going to work.

 

[mistercrash]

To one of you guys who know what they are doing, please send the price you want for a complete unit I can just hook up to a battery and use for myself. PM me with your price with shipping included to Guelph, Ontario, Canada.

Thanks
Ray

 

[riba2233]

To one of you guys who know what they are doing, please send the price you want for a complete unit I can just hook up to a battery and use for myself. PM me with your price with shipping included to Guelph, Ontario, Canada.

Thanks
Ray

Can you hold on just for a little until I do some final tests?

 

[Alan B]

Great thread. Interesting idea to use battery pack, perhaps a a lithium nanotech pack would work, perhaps in conjunction with a smaller capacitor?

What is the current flow during welding?

 

[riba2233]

That's actually a good question and I don't have the exact numbers since it's hard to measure. But I would say it's about 300-400 A in my case, for 0.1 mm nickel tape.

 

[mistercrash]

To one of you guys who know what they are doing, please send the price you want for a complete unit I can just hook up to a battery and use for myself. PM me with your price with shipping included to Guelph, Ontario, Canada.

Thanks
Ray

Can you hold on just for a little until I do some final tests?

No problem, PM me when you're ready.

 

[riba2233]

OK, I hope it will be soon

 

[ridethelightning]

im also interested.
let us know when you have a price.

 

[riba2233]

Sure, no problem!