Due to many requests for the PCBs

I do currently have some PCB Sets and prebuilt kits in stock. Take a look here:


You can also take a look in the comments below this instructable. Some people who ordered boards at PCB manufactures are willing to sell some of them.

Update 03.2017
The Spot Welder has a new PCB layout ! Improvements in the V2:

  • only one mosfet driver instead of four
  • changed electrolytic capacitor to film capacitor
  • capacitors closer to the mosfet driver
  • wider pcb traces for high current paths
  • added gate resistors for the mosfets
  • aluminum u-shaped part for the mosfet board (much easier to assemble)
  • general pcb layout improvements
  • pcb is now designed in KiCad (more open source than Eagle)

An Arduino Nano based Spot Welder for battery welding

This Spot Welder can be used to weld 18650 batteries. It needs a 7-12V power source (12V recommended) and uses a 12V car battery as welding current supply. Typically one 45Ah battery delivers enough current to get good welds with 0.15mm nickel strips. For thicker nickel strips maybe you will need bigger battery or two in paralell.

The Welder generates a double pulse, where the first one is 1/8 of the time of the second one. Pulse time of second pulse is adjustable by the potentiometer and displayed on the screen in mS so you can exactly adjust the time. Its adjustable from 1 ... 20 mS.

Watch the Video to get detailed instructions on how to build it.


Project Files: (BOM, pcb files, aluminum template, arduino code...)


Step 1: Making the PCB (V2)

You can find the Eagle / KiCad files for the PCBs on my Github.

Files for Spot Welder V2

Files for the previous Version

Easyest way is to order the boards at an PCB manufacturer. For example at pcbway.com .There you get 10 boards for about 25 €. The necessary gerber files for ordering at pcbway.com can be found in my Github.

You can support me by registering through this link http://www.pcbway.com/setinvite.aspx?inviteid=128...

This way you get a 5$ coupon for your order and i get some percent discount on orders for upcoming projects.

But if you like diy you can also build it on a prototype pcb board with hand wiring. This is how i did the first prototype of the spot welder. In the pictures you see a manufactured board looks much cleaner.

(Update 12.2016)

The trace that connects the two boards in the combined gerber is only a ground connection not needed for the spot welder to work. It is only there to make clear to the pcb manufacturer that this is meant as one board and they dont need to make v-cuts or something else. With this modification it is possible to order at pcbway without problems.

<p>Few comments regarding V2 : <br>- do we really need 8 gate resistors for the mosfets? Woldn't 1 be enough?<br>- space under Arduino can be used for TTH parts, too.<br>-<br> people with good soldering skills can upgrade V1 with gate resistors, <br>too. Gate resistor can be soldered between DIP socket and board. For <br>other pins, piece of wire can be used.</p><p>Kudos for V2! It came out before I managed to finish original version!</p>
<p>Since the new version only has one driver for all mosfets, each of the mosfets should have its own gate resistor. On the V1 each mosfet had its own driver output and therefore gate resistor were not as critical as on the new v2.</p>
<p>Is there a special reason to use a mosfet driver instead of using mosfets with logic-level gate?</p>
<p>BTW, I have 8 boards in Russia, Kazan. 5 USD/board </p>
<p>Hello! I've made welder V1, but it doesnt' work. Mosfets are constantly open, so when i put wires to the battery- I got continuous current and melted wires, even with button not pressed.</p><p>Aduino wokrs fine, D5 doest from 0 to 5v and back to 0 when I press the button, LED blinks, display shows ms, MCP drivers seems to be fine- but ...</p><p>What should I check? </p><p>Thank you in advance.</p>
<p>How do I calculate the gate current? Also if someone could tell me the exact current requirements for spot welding to happen.</p>
<p>Also, why are the gate resistors needed?</p>
<p>Hi!</p><p>I wanted to make similar project, but I can't find IRF3704 mosfets anywhere. If anyone could suggest me some alternatives or give me links for IRF3704, it would be absolutely great!</p>
<p>Use IRF1405 </p><p><a href="https://www.reichelt.de/Transistors-IRC-IRF-/IRF-1405/3/index.html?ACTION=3&GROUPID=2891&ARTICLE=41600&OFFSET=75&" rel="nofollow">https://www.reichelt.de/Transistors-IRC-IRF-/IRF-1...</a></p><p>IRF3704 can not carry enough current.</p>
<p>10 IRF 3710 won't do the job?</p>
<p>hi, i build the spot welder and now a make an add-on. </p><p>the problem is to work with two hands to hold battery and wire.</p><p>there are two RC_Servos MG996 .</p><p>Two springs at the upper back of the servos for the right thrust pressure of each servo for itself.I just connected the foot switch to the reed relay of the addon board.<br>So you can leave the spotwelder platine as it is.</p><p>Next, a plexiglass shield with LEDs is attached to protect the eyes, to tilt with switch and a runstop switch. safety first</p><p>see the video on youtube </p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/W3eWHlKxAPY" width="500"></iframe></p>
<p>Matze, that is an awesome construction you made there. Love it.</p>
<p>Hello everyone, my foray into electronics begins here, I'm an oldie but a goody, in my opinion, I love to tinker, a very fussy builder of RC planes, helis and Hexacopter, race go-karts in the 125tag class for seniors so I have plenty to play with.</p><p>I have just ordered 10 spot welder PCB's from PCBWay with both PCB's on the one board, and had a look at the Gerber files as a matter of interest and it shows a trace that runs between the two designs, when the PCB gets cut in half this trace will be cut. I'll assume that this is a manufacturing link between the 2 designs, is this correct, see image for my minor concern.</p><p>Some of these boards will be available at cost + shipping if anyone is interested when they arrive.</p><p>Cheers</p><p>Graham </p>
<p>Do you have any board sets left for the spot welder? Please let me know how much? Thanks in advance!</p>
<p>I do, AUD $5.00 + postage</p>
<p>I suspect it is a link so the boards are &quot;one&quot; for manufacturing. See attached photo (red trace) The arduino nano has two ground pins and this connection is probably needed. But if you prefer to have both GND pins on the arduino connected solder a jumper (see attached photo blue trace) to either of the JP1 terminals. The blue trace should probably be added to the v2 eagle files. Can someone make the change?</p>
<p>The last paragraph in Step 3 covers the earth between the 2 boards at JP1 &amp; JP2:</p><p>&quot;- In the new Version you have to connect JP1 on the Arduino Board with JP1 on the Mosfet Board and JP2 on the Arduino Board with JP2 on the Mosfet Board. Use pin headers and sockets. These jumpers connect the ground of the two boards&quot;</p><p>Thankyou for the reply cnewlander</p>
<p>Sure, but the extra GND pin on the Ardunio remains unconnected. I was suggesting to connect it and proposed a method.</p>
<p>Hey Graham, I'm interested in a set. Please let me know when you get them.</p>
No problem at all, cost of the pcb's was AUD $6.70, let me know if you wish to proceed.<br><br>cheers
<p>I could not find information on the size of bolts used to attach the MOSFETs to the board and aluminium plate. Size M4 could not go through the board and MOSFETs without widening the holes. Size M3 seem a bit too mall for the purpose. Please, share your experience.</p>
<p>I've just used rivets. Do the jobs perfectly. The only problem being if I need to replace mosfets! :-)</p>
<p>M3 x 10mm fit perfect if your aluminium is 4mm thick</p>
<p>If anyone in the UK needs a PCB just drop me a message, I have a few spare boards available from my build.</p>
<p>I cant find the list for all the required parts :( help</p>
<p>Thanks. Nice red pcbs from KaeptnBalu tindie store. Received on west coast of USA within 8 business days. Also purchased diode set. Cost is cheaper when digikey or mouser shipping is factored in.</p>
<p>Cutted Boards available in france, worldwide shipping, PM me if you want one or more :)</p>
<p>I have same spare sets of board in Italy. If interested, contact me.</p>
<p>I have others spare sets of board in Italy. </p><p>I have also a aluminium strip 5 mm.</p><p> If interested, contact me</p>
Whats up sir. I am interested in building this. Do you still have boards available? Im in USA though. Also, will this work with Arduino UNO?<br>Thank you<br>R. Burgy
<p>Hi Guiseppe,</p><p>Boards received, thanks for quick shipping!</p>
<p>Dear Giurti,</p><p>I am looking for one set of PCB's for the Battery Spot welder.</p><p>If you have one set available, please sent me the cost including shipping cost to the Netherlands.</p><p>Regards,</p><p>J.A. Seegers</p>
Hi KaeptnBalu. Ive made the welder, for now without dhottky and tvs. At first i was using a too small section cables, and it was not working properly. Then Ive adopted a thicker section cables and now its working nice. I have a question though. The drivers datasheet says: &quot;To operate the MOSFET driver over a wide frequency<br>range, with low supply impedance, a ceramic and low-<br>ESR film capacitors are recommended to be placed in<br>parallel, between the driver, VDD and GND. A 1.0 &micro;F,<br>low-ESR film capacitor and a 0.1 &micro;F ceramic capacitor<br>placed between pins, 6 and 3, should be used. These<br>capacitors should be placed close to the driver to mini-<br>mize circuit board parasitics and provide a local source<br>for the required current.&quot; Now on the board you only used a couple of such capacitors. But I think each of the drivers should have its own couple. What do you think?
<p>I have others spare sets of board in France. I have also a aluminium strip 5 mm. Actually we can use <a href="http://batteryrecover.com" rel="nofollow">this method</a> to renew any batteries. Thank you John !</p>
<p>Can someone give the value or part number of potentiometer please.</p>
<p>Anyone created a 3d printed case for this yet? If so, would you mind sharing the STL files for it?</p>
<p>check this out. Its a parametric box creator, so you can print an enclosure for your project cut to fit! Very cool</p><p><a href="http://www.thingiverse.com/thing:1355018" rel="nofollow">http://www.thingiverse.com/thing:1355018</a></p>
<p>I've build an enclosure for my spot welder ... put it on thingiverse for everyone else with a 3d printer ... it's not perfect but better than nothing ;)</p><p>http://www.thingiverse.com/thing:2117338</p>
<p>Edit function missing ... link is not a link ... retrying ;)</p><p><a href="http://www.thingiverse.com/thing:2117338" rel="nofollow">http://www.thingiverse.com/thing:2117338</a></p>
<p>I have others spare sets of board in Italy. </p><p>I have also a aluminium strip 5 mm. </p><p>If interested, contact me</p>
<p>Nice and Nit project, Congratulation </p><p><a href="https://www.instructables.com/member/KaeptnBalu/" rel="nofollow">KaeptnBalu</a></p><p>And thank you for sharing with everyone, you are a true enthusiast and hobyist,</p><p>So far i only didnt notice the value for Trim Potentiometer,</p><p>Very Best Ragards.</p>
<p>I ask if you beleave need add a fuse protecting for axcidental short circuit.</p><p>What kind of fuse can I add?</p>
<p>KaeptnBalu, there have been several threads elsewhere (endless-sphere) about it being a good idea to add a TVS diode and a Schottky, to help dissipate avalance current. Have you reviewed this and think it's a good idea or necessary for your design? Also the suggestion of adding ~82 Ohm resistors between the FET drivers and the FET gates. Thanks for your work on this!!</p>
<p>Do you have a link to the thread with the information so i can take a look ?</p><p>I have done several hundres welds with the spot welder and there was no problem so far. Therefore i did not think about adding more parts to it.</p>
<p>Adding the TVS is redundant. THe mosfets specified in the BOM have builtin TVS diodes.</p><p>Adding the schottky is a good idea.</p>
<p>@ake- You&acute;re referring to the body diode? How much energy are you assuming that these are capable of dissipating, if not using a clamping circuit? $2 TVS for $20 of mosfets might not be a bad idea.</p>
<p>I did some measurements and with the shottky diode only there are crazy voltage oscillations which make the spot welder freak out. You can see it in the step i added to the instructable. With Shottky+ tTVS everything works fine.</p>
Here's a thread that mentions your system. https://endless-sphere.com/forums/viewtopic.php?f=14&amp;t=83411
<p>Any thoughts on this? The mod seems to help extend life of mosfets greatly.</p>
<p>I will do some oscilloscope tests soon. And if its good add the diodes to the future prebuilt kits. You can already get them on my tindie store f you want to upgrade your existing spot welder. I do also have a little wiring diagram there. </p><p>https://www.tindie.com/products/KaeptnBalu/diy-arduino-battery-spot-welder-diode-set/</p>

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