Recommended is at least a 12V 400A (CCA) car battery. The 600A (CCA) car battery size turned out to be the optimal power to weld all kinds of nickel strip. I do not recommend to use a so called “deep cycle” battery. They look like a car battery but these are not made to deliver very high currents for a short time. They are meant to deliver little current like 20A to 50A for some hours. They are maybe capable of delivering the high welding current, but could be damaged after some welds.

Please do not connect and use the welder on a car battery that is still installed and connected to your car. Especially not while the car is running. This could cause errors in the car electronics.

The Spot Welder works with 3s Lipos only. 4s or more cell lipos have a to high voltage for the welder. It does need 400A current at least to do good welds. The maximum current should not exceed 800A. You can calculate the maximum current your Lipo can deliver by muliplying the C rate with the capacity. For example: 5Ah (5000mAh) x 130C = 650A (650000mA) maximum theoretical current.

The following Lipos have been tested and approved to work good with the spot welder:

store=en_us” target=”_blank” rel=”noopener noreferrer”>Turnigy Nano-Tech 5000mAh 3s 65-130C or

SLS Quantum 5000mAh 3S1P 11,1V 65C/130C

You should use 0.1mm to 0.25mm nickel strips. Typically 0.15mm nickel strip is good for all standard applications.

0.3mm nickel strip is possible if the pulse time is increased to about 50ms (this time was set with a 440 A or CCA car battery). Also try to use slotted nickel strips if you want to use 0.3mm ones because the slotted ones give you better welding spots with less current or shorter pulse time.

The PulseTime highly depends on how strong your welding battery (car battery or lipo) is and what welding cables you use. Here are some PulseTimes as a basic orientation used with a 400CCA 12V car battery and the welding cable set from the shop.

• 0.15mm nickel strip: 20ms
• 0.2mm nickel strip: 26ms
• 0.25mm nickel strip: 35ms

You can use any switch that is NO (normally open). The foot switch does not carry any current, so even very tiny switches will work. (Example foot switch) . Do not wrap the foot switch wire arround a welding cable and try to make a hand switch. This can damage the Spot Welder because of inductive voltage.

Make the cables as short as possible. I recommend 10mm² (7awg) or 16mm2 (5awg) 0.5m for each cable. If you make the cables longer the welding pulse will become weaker unless you use thicker cable. Also it is more likely that you damage the Spot Welder with very long cables because of the high inductive voltage that is generated in longer cables.

The V3 does not need a seperate power supply for welding times below 50ms. It can be directly connected to the car batteries or Lipos positive pole. For the older V2 a 12V 2A or 1A power supply works good. Alternatively a 3s Lipo / Liion battery also works perfectly.

Yes in the new V3 you can directly power it from the car battery or Lipo for welding times below 50ms. For V2 or older in the standard configuration you need a seperate power supply or battery.

But if you add a 470µF 25V capacitor between the Arduinos Vin and GND you can power the V2 and older Arduino Board from the car battery. More infos on the Mod

No, you need a car battery or Lipo. A pc power supply can not give you enough Amps to weld. You need at least 400A. Typicall power supplys can deliver maximum 50A. Also power supplys usually dont like to be shorted, which is what the welder does.

Yes, some jump starters may work with the spot welder. I made a blog post about this topic. Please read it to find out what jump starters you can use.

Your Arduino Nano board may be damaged and needs replacing.

Power Supply:

The strength of the welds highly depends on the power supply of the spot welder. Your car battery or Lipo should be able to supply 400 – 600A current.

To get the best results it is recommended to use a 600A (CCA) car battery or a Lipo that can do that much current. (e.g. 3s 5000mAh 60-130C)

Nickel Strip:

Depending on what size nickel strip you are using you need to choose the right power source. Welding 0.1mm to 0.15mm nickel will work ok with a 400A current. But to get good welds on 0.2mm  or even thicker you need about 600A current.

Pressing Strength:

Its also important how hard you press the welding tips against the nickel while welding. You need to apply some pressure (about 1 kg). But dont push very hard because this will reduce the weld strength again.

By pressing hard once prior to welding, then holding the spot welding leads lightly, you should be able to get great bonds..

This effect is normal on DC Spot Welders. It is the strongest in the first few milliseconds of the weld. Which means it will be more noticeable on very short pulse times.

It can be counteracted a little bit by using differnt pressure on the welding tips. Push the positive electrode a bit harder against the nickel or the negative electrode a bit less hard.

Most of the time when the oled display stays black its a problem of the Arduino Nano. The display will only turn on if it gets a valid signal.

First try to reupload the software to the Arduino Nano again. See the Tutorial

If this does not help it could also be a contact problem of the pin header of the display. Remove the 2 screws that hold the display in place and unplug it from the socket. Then plug it back in.

Should you have a spare Arduino laying arround (it does not have to ba an Arduino Nano) you can upload the Spot Welder Software to it and connect the display to it to confirm the display does work. This way you would now for sure the defective part is the Arduino Nano.

Otherwise the Arduino Nano or the display needs to be replaced.

When you connect the Arduino Nano to your computer with an USB cable it should automatically install the drivers for the Arduino Nano.

If it does not, you need to install the driver for the USB chip manually. CH340 Windows Driver – CH340 Mac Driver – CH340 Linux Driver

If replaced, we have had reports that some Arduino Nano clones may require a slightly different uploading process from the one listed in our Software Installation Tutorial and so check the Arduino Forums for different uploading solutions.

Most of the time its a problem with the driver for the USB controller chip on the Arduino Nano Clone (CH340 Chip). Deinstalling the driver in your device manager and reinstalling or changing to an older driver version may help.

The official Arduino Support Website has a great tutorial how to switch to an older driver version.

In some cases it also helps to use an older Arduino Nano IDE Version (1.8.9) instead of the latest version.

Another common problem is the wrong processor selected. (In the Arduino IDE in the menu point “tools”) For older Arduino Nanos select Processor: “ATmega328p (Old Bootloader) or for newer Arduino Nanos Processor:”“ATmega328p”

After many hundreds of welds the welding tips will wear out. You can “refresh” them pretty easily by sanding with sandpaper or a file. The tips should always look clean for best welding results. If there is to much “burnt stuff” on them it can cause bad electrical contact to the nickel strip.

If you damaged the tips so bad they can not be sanded anymore you need to replace them or get a new welding cable set. There is a Welding Tip Change Tutorial available.

Weld Mode Setting

First check if you set the welder to the right welding mode. If it is in manual mode it will not activate a weld pulse automatically. Only if the foot switch is pressed. If it is in auto mode you can not activate the weld pulse by pressing the foot switch. It will automatically be triggered when both welding tips touch the nickel strip.

Hardware Problem

If it only works in auto mode but not in manul mode the foot switch could be defective or connected wrong. Check the assembly guide to see how the foot switch needs to be connected.

If it does not activate a pulse at all or instantly welds (short circuits) there is most likely a hardware defective on the welder. To find out which part it is you need a multimeter for some measurements.

Then you could do the folowing:

Check the voltage at pin D5 of the Arduino Nano. That should be 0V and only go up to 5V during a pulse activation.
If its always 5V its an indicator the Arduino Nano has failed.

Next check the voltage at the 8 pin header that connects the mosfet board and the arduino board.
There should be about 0V. If it always is 12V while there is 0V at Pin D5 of the Arduino Nano its an indicator that the MCP1407 mosfet driver has failed.

Another thing that could have failed is one of the 4 big protection diodes on the bottom of the mosfet board.
The damage of these is usually visible by cracks in the case of the diode or black burn marks arround the failed diode.
If these fail they tend to short out.

You can also measure the resistance between the 2 aluminum parts (with the welder switched off). That should then read about 1k Ohm or 150 Ohm on older welders.
If its close to zero it is most likely caused by a defective protection diode.

Weld Mode Setting

First check if you set the welder to the right welding mode. If it is in manual mode it will not activate a weld pulse automatically. Only if the foot switch is pressed. If it is in auto mode you can not activate the weld pulse by pressing the foot switch. It will automatically be triggered when both welding tips touch the nickel strip.

Hardware Problem

If it only works in auto mode but not in manul mode the foot switch could be defective or connected wrong. Check the assembly guide to see how the foot switch needs to be connected.

If it does not activate a pulse at all or instantly welds (short circuits) there is most likely a hardware defective on the welder. To find out which part it is you need a multimeter for some measurements.

Then you could do the folowing:

Please take a look at the mosfet board and check if there is any visible damage to the 6 mosfets or the 3 diodes on the bottom of the board.Like cracks in the components housing or burn marks on and around the components.

If that looks good (no damage)  you can measure the resistance between the two aluminum parts. For this the mosfet board needs to be attached to the top half of the welder. It should be about 1000 Ohm.  If it’s only 1000Ohm when the welder is switched off, but 0 Ohm when the welder is switched on, it’s a problem of the control electronics. (Arduino Nano or Mosfet Driver Chip)

Check the voltage at pin D5 of the Arduino Nano. That should be 0V and only go up to 5V during a pulse activation. If it’s always 5V or even higher it’s an indicator the Arduino Nano has failed.

Next check the voltage at the 6 pin header that connects the mosfet board and the arduino board. There should be about 0V. If it always is 12V while there is 0V at Pin D5 of the Arduino Nano it’s an indicator that the MCP1407 mosfet driver has failed.