Can I modify the wire gauge or length on my kWeld spot welder?

Understanding the importance of welder circuit inductance

Your kWeld spot welder comes with a set of standard wires that many are tempted to replace. We encourage the DIY mindset and appreciate you sharing your modifications and experiences with the kWeld World community.

This article is written to help you understand how changing the length and diameter (gauge) of the wires impacts inductance.

Firstly, please understand that excessive inductance can damage the kWeld unit. Increasing the wire length and the associated inductance also reduces the maximum current your kWeld can safely handle. Therefore, during setup, the sum of all wire lengths is entered in the "CableLen" setting.  The software will then limit the maximum current and protects the kWeld spot welder.

Let's try to explain inductance using an analogy that might be easier to visualize. Consider the waves formed by the wind on the ocean. The stronger the wind and the larger the body of water (fetch), the more imposing the waves. In the case of your welder, the electric current - measured in amperes - can be compared to this wind, while the wire length can be likened to the surface of the water on which the wind acts. Thus, inductance would be represented by the waves formed under these conditions.

Clear so far? Let's then explain why large waves are threatening to the longevity of your kWeld spot welder.

The kWeld spot welder can be likened to a highly sophisticated switch, with the MOSFET as its key component. This welder is equipped with six MOSFETs and is designed to handle currents of up to 2000 amperes.

Continuing with the analogy, let's imagine a bay on the ocean with a dam at its end. This dam is designed to withstand long-term use, taking into account specific parameters such as the maximum wave size based on the region's wind history.

Now, suppose a geological event opens the bay to the ocean, increasing the fetch. The waves generated by normal winds would be much larger than what the dam was designed for. The large waves crashing into the dam will lead to excessive stress and ultimately the dam's failure.

Is it worth changing the wire diameter? I could try to continue the analogy using the depth of the water and its effect on wave shape, but I believe it suffices to say that wire diameter has a relatively minor impact on this equation.

Your welder comes with a total of one meter of 8-gauge wire. Eighty centimeters are allocated to the electrode side, meaning the input wires are only ten centimeters long. It would certainly be desirable to lengthen these wires to offer more flexibility in the welder's placement. However, this modification could be detrimental to the welder. We therefore recommend using the wires included in your kWeld kit. It is also important to add any additional length, such as the wires between the terminals and the connector of a LiPo battery, for example, and to adjust the "CableLen" parameter.

Here is a graph illustrating the relationship between the total wire length and the corresponding maximum capacity of your kWeld spot welder. This graph, along with a more in-depth discussion of inductance, is available in the kWeld manual, accessible in the Resources section on the GridRewired.com website.