I would suggest there are three common options that do this well.
Option 1:
The least expensive option is to use a larger lead acid car or truck battery. Lead acid batteries are actually very well suited for this application. They are built to provide a lot of power for a short time such as is used by the starter motor on an internal combustion engine. We would suggest that a healthy, but not necessarily new, 800-900CCA (cold cranking amps) battery is a good choice. It should be able to provide more than 1500 amps for the milliseconds that are required by the kWeld spot welder. The main drawback with this set up is that the spot welder must sit between the terminals in order to keep the length of the wires short, and inductance as low as possible. Keeping a battery minder or solar charge controller connected to your battery will ensure it is always ready to go.
Option 2:
If portability is required, it may be a better choice to select an appropriate LIPO (lithium polymer) battery. These are used in the RC world and can provide the needed jolt of energy despite their small and light form factor. The downsides to this option are that, unlike lead acid batteries, providing maximum power is harder on the battery and LIPO batteries tend not to last as long. Once they swell up, they should be discarded responsibly and replaced. LIPO batteries can be quite expensive and require specialized chargers. They are also known to catch fire and special precautions must be taken to avoid burning down the house. Keeping your batteries in a fireproof bag and not charging them when unattended are examples good practices.
Option 3:
keenlab, the manufacturer of the kWeld does provide a good solution. The kCap ultra-capacitor module will provide 1300+ amps at 8.2v. This module can recharge very quickly and provide consistent, repeatable power surges needed for quick work. The kCap module can be charged at 70amps by the kSupply board. Alternatively, a suitable bench top power supply that can be voltage regulated may be an option, albeit slower. For those looking for maximum performance, two kCap modules can be connected in parallel and charged to about 7.8 volts to provide about 1850 Amps of current at the electrode tips. A single kSupply can be used to charge the doubled up powerhouse.
Perhaps the best feature of the keenlab line-up is that, given the multiple setup options, it is possible to first start with the simplest option 1, and upgrade your system at a later time.
We'd love to see a picture of your setup! Share your thoughts and pictures on the kWeld World Facebook group.
Get in touch with your comments or questions by writing to info@gridrewired.com
]]>Your kWeld spot welder came with a set of stock wires which many are tempted to change. We encourage the DIY mentality and love the fact that you rewire masters share your mods and experiences with the community on kWeld World.
This article is written to help you understand the impact changing wire length and diameter (gauge) can have on inductance.
Firstly, please understand that too much inductance can damage the kWeld unit. Increasing the wire length and related inductance also reduces the maximum current your kWeld can handle safely. Hence, in the setup, the wire length is entered in order for the software to limit the maximum current and protect the kWeld spot welder.
In the manuals, Frank at keenlab discusses the inductance calculations at length. Here, we’ll try to summarize the impact of changing wires with one example. We will also link the related charts and an on-line inductance calculator so that you can explore the impact of your desired changes.
In this example, the kWeld is powered by a 12V deep cycle lead acid battery. It is capable of 1000CCA. The rewire master in this example wanted to lengthen the power cables using 4 AWG cables measuring 56cm each (22”).
In this chart, you will notice that the total circuit inductance in not equal to the addition of the two smaller circuits. This complicates the calculation for a change of only the power supply cables since the new cables are a different gauge. The method used in this following chart was to average the wire diameter out over the entire circuit to find a value for comparison.
Each wire is added in this manner: (8AWG) 40cm + 40cm = 80cm, (4AWG) 56cm + 56cm = 112cm, Total wire length is 192cm. The 8AWG wire has a diameter of 0.33cm, the 4AWG wire has a diameter of 0.52cm. The average diameter over the full length of wire is 0.44cm.
You can see that this change more than doubles the total inductance in the kWeld circuit.
In order for you to calculate inductance for your desired change, we include here and on our resource page, some links to the resources we used for these calculations.
Wire gauge to diameter conversion chart.
Submit your question so that we can build a useful Q&A
info@gridrewired.com
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