DIY Arduino Battery Spot Welder Prebuilt Kit V3.2.1


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Rated 5.00 out of 5 based on 7 customer ratings
(7 customer reviews)

In stock

SKU: sw-pbkit-v3 Category:


What you get:

  • basically you get what you see on the product pictures
  • A prebuilt kit of the spot welder V3.2.1 with all the electronics already soldered to the pcbs.
  • 4 M3 screws with nuts to screw the two pcbs together sturdy if you like. (They also stay together without the screws installed)
  • The Arduino is programmed with the latest version of the spot welder software.
  • All kits are assembled and tested at our shop in germany
  • you need to order accessories like welding cables, battery terminals etc. extra

Please read the Quick Start Guide before using the Spot Welder !

Minimum Setup to start welding:

  • Prebuilt Kit
  • Welding Cables: 2 about 50cm long, high flexible 10mm² welding wires with solid copper welding tips and crimped cable shoes.
  • Car Battery (recommended 12V 400…600 CCA)
  • Battery Terminals
  • about 30cm thin wire to connect 12V to the Spot welder PCB

Additional parts that can be added:

  • Foot Switch: to activate the welding pulse manually if you dont want to use the AutoPulse feature.
  • ANL 300A Fuse: to protect the Spot Welder in case of a failure
  • Case Kits (Fuse Case, Spot Welder Case)
  • Extension Cable: needed for the fuse case and if you are using a lipo battery as welding current supply also for the Spot Welder case

The new V3.2 of the prebuilt kit can be finished without soldering required. All pcb files, part list, Arduino code… can be found at my Github page. More detailed information can also be found at the instructables and in the video.

Update 02.2018

Improvements in the V3.2.1:

  • Arduino software update that enables the measurement of pulse voltage and pulse current

Update 01.2018

Improvements in the V3.2:

  • the Arduino Board was updated so it does now come with a terminal block installed to the 12V and GND input pads. This way the prebuilt kits can be finished without soldering.
  • the voltage measurement now connects directly to the 12V input pad instead of behind the schottky diode. This guarantuees a more precise voltage measurement.
  • the 8 small SMAJ13A-13-F TVS diodes have been removed from the mosfet board. There is now one of these diodes on the Arduino board that protects all mosfet gates at once.

Update 12.2017

Improvements in the V3.1:

  • 4 SMD TVS diodes in parallell on the Mosfet PCB
  • with the 4 diodes installed it is possible to use car batteries up to 800CCA

Update 09.2017

Improvements in the V3:

  • Mosfet PCB now with 2oz copper layer and wider traces which connect the high current carrying mosfet legs to the u-shaped aluminum part
  • “AutoPulse” feature, which automatically activates a pulse after a defined delay time when both welding tips touch the nickel strip (thanks to Petr Zverina for the idea)
  • 7 segment display replaced by OLED display
  • potentiometer replaced by rotary encoder
  • Menu system to easy adjust the low battery alarm, AutoPulse delay and short pulse time
  • powered directly by car battery, no more need for extra power supply
  • TVS diode integrated on the mosfet pcb, no external diodes necessary
  • upgraded Mosfets to IRFB7430 (they can handle up to 1000A welding current with no problem)
  • Standby feature: after 5 minutes of inactivity the Spot Welder will go to standby and the foot switch and AutoPulse will be deactivated while in standby.
  • u-shaped aluminum parts is now riveted to the pcb

What is it?

An Arduino Nano based Spot Welder for battery welding

This Spot Welder can be used to weld 18650 batteries. It  uses a 12V car battery as welding current supply. Typically one 40Ah 440A battery delivers enough current to get good welds with 0.15mm nickel strips and even 0.25mm 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 12% of the time of the second one by default. Pulse time of the main pulse is adjustable by the rotary encoder and displayed on the screen in ms so you can exactly adjust the time. Its adjustable from 1 … 100 ms by default. (adjustable up to 500ms in the system menu)


The new menu and OLED display features:

The main screen shows the Pulse Time (adjustable by turning the rotary encoder), the battery bar, the total welds done and if the AutoPulse feature is activated.

You can enter the menu by “clicking” / “pushing on” the rotary encoder.

  • Auto Pulse: Here you can turn the AutoPulse on or off and set the delay time. The “AutoPulse” feature automatically activates a pulse after a 2 second delay (default) when both welding tips touch the nickel strip. If it is activated you can not use the foot switch to activate a pulse. The main screen will show “AUTO” in the right bottom corner if it is activated and “MANU” if it is deactivated.
  • Batt Alarm: you can set the voltage at which the battery alarm should be triggered (default 11V). If the alarm gets triggered the spot welder will stop working and show a low battery warning until a voltage higher than the set battery alarm is reached. (typically after recharging your battery)
  • Shrt Pulse: you can set the duration of the short pulse in %  (1 …100) . For example if it is set to 10% and the main pulse is set to 20ms the sort pulse will be 2ms. The short pulse will always be at least 1ms no matter what % value is set. So if the  main pulse is 5ms and short pulse is set to 10% it will still be 1ms and not 0.5ms.

There is also a system menu available. To find out about all its functions please read the Quick Start Guide


Customer Batteries built with the “DIY Arduino Battery Spot Welder”

Video on how to use it:

(Assembly starts at 0:48)

Additional information

Weight 120 g
Dimensions 75 x 51 x 40 mm

7 reviews for DIY Arduino Battery Spot Welder Prebuilt Kit V3.2.1

  1. Rated 5 out of 5

    Luigi (verified owner)

    I bought the welder (one month ago) and am very satisfied.
    it is very well assembled except the display that looks a little unstable if it is touched. It’s not a problem because I put it all in a plastic box that holds the welder.
    I do not use a car battery but a 300A jump starter (suaoki) that is small and light and everything works smoothly.

    • Marc Schoenfleisch

      Thank you for the positive feedback. The display problem has been fixed. All prebuilt kits from now on come with the display mounted on 12mm standoffs to the pcb.

  2. Rated 5 out of 5

    Carlo.c (verified owner)

    Hi today i got my kit fast delivery i tested nicely and thats very good i am satisfied.

  3. Rated 5 out of 5

    Bradley Tompkins (verified owner)

    Delivery was fast to the USA, about a week. The welder works wonderfully and its performance has gone beyond my expectations. Thank you for producing such an affordable kit that works so well.

  4. Rated 5 out of 5

    Damien Milk (verified owner)

    My welder arrived in remote West Australia yesterday, and after a small amount of assembly, it was up and running. Straight away it was producing first class welds, solid and reliable. Its easy to use, professionally crafted and more than affordable.

  5. Rated 5 out of 5

    Florian Münter (verified owner)

    I bought the spotwelder a while ago and it works really really good. I spotweldet a battery for my electric mountainbard with 3 layers of nickel stacked on top of each other with no problems. The kit came pre-assembled and the instructions were very clear. Very good product!!

  6. Rated 5 out of 5

    Frank Ortisi

    I just bought this thing about 2-3 wks ago, assembly into the cases were a breeze, very well made kit!
    I purchased a used battery locally for just $30 then went on to build my first two battery packs, VERY pleased with the operation and quality of this tab welder! TY!

  7. Rated 5 out of 5

    Joshua R (verified owner)

    I purchased one of the v3.2 kits and it is one of the best items I have owned. I tried other avenues, home built options, the Sunkko setup, etc…. but none compare to the quality and ability of this welder. I am using a 3S Lipo pack rated for 5000mah and 60C with no problem. I have welded up to .25mm nickel plated steel strips easily and it keeps going. If you are looking to get into spot welding, save your time and money and go with this one. Some of the welding boxes seen on Amazon, Alibaba, etc…are okay, but are twice the cost and a fraction of the quality.

    The version 3.2.1 looks even better and I am tempted to get a new setup and use my existing as a back-up – it is that good. Make sure you have sufficient battery C or CCA rating, that would be the only issue I have had and it was easily corrected.

    Great product, hands down


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