There is no generally supported, safe conversion recipe in the available documentation for turning a battery charger into a spot welder. In particular, the KEKK K100 control-board manual says not to power that board with a charger. Battery-tab welding uses brief, high-current pulses, and documented projects use purpose-built capacitor or battery power sources—not a generic charger conversion.
Why a battery charger is not automatically a spot-welder power source
A charger is designed to charge batteries under its own operating conditions; that does not establish that it can deliver the brief, high-current pulse a spot welder needs. The sources available here do not establish a generally safe or compatible way to modify a charger for that job. Charger and welder designs differ, so this is not proof that every conceivable combination is identical; it is a reason not to assume compatibility or follow an unsupported wiring recipe.
The distinction matters even for a control board marketed for DIY spot welding. The KEKK K100 manual lists a working voltage of 9–16 V and describes capacitor and lead-acid battery configurations for that kit. It explicitly says not to use switching supplies, transformers, chargers, or power banks to power its board. That warning applies to the K100 as described in its manual, not necessarily to every spot-welder design. Read the KEKK K100 manual.
What battery-tab spot welding involves
For cylindrical battery cells, such as 18650 or 26650 cells, the documented task is joining nickel strip to a cell terminal. In Ian Hooper’s 2012 ZEVA project, the capacitor bank supplies a brief pulse that locally melts the strip. Hooper emphasizes that the weld current should pass between two points on the same side of the battery terminal—not through the battery. This is project guidance, not a complete design specification or safety certification. See the ZEVA capacitor-discharge project.
#1 Best Overall
- 【Ergonomic Principle】 - The hand-held pulse spot welding pen adopts the ergonomic concept, the appearance is slim and easy to hold, and it provides the user with the greatest convenience.
- 【LED Lighting Function】Dual LED high-brightness lighting device, the spot welding operation is clear at a glance. Precision spot welding in low light environment, spot welding at night, and efficient spot welding for employees with poor eyesight.
- 【Fixed Welding & Welding Pen】Fixed welding head can weld 0.05-0.35mm thick nickel-plated nickel strip, 0.05-0.2mm pure nickel-nickel strip. The soldering pen can weld 0.05-0.2mm thick nickel-plated nickel strips and 0.05-0.15mm pure nickel-nickel strips.
- 【Foot Welding】 - The spot welding machine is equipped with a foot control interface and a foot switch, which makes welding more precise and reliable. The welding pressure regulator can continuously adjust the welding needle pressure from 300g to 700g, which is convenient for welding workpieces of different thicknesses.
- 【Wide Application】 - Used for welding multi-row lithium battery pack, electric vehicle battery pack assembly and maintenance. Also suitable for coin cell batteries, battery packs of various sizes, cell phone cameras, stainless steel.
That current path is a key part of the battery-tab application: the electrodes contact the strip at two nearby points on the terminal side, so the intended weld current does not travel through the cell. It is not a reason to improvise electrode placement or use an unverified power source.
Documented designs use different power architectures
Two project examples illustrate why one design cannot be treated as interchangeable with another:
Rank #2
- Two types of Trigger Flexibility & Safety: The maximum current is 1,380 A, and the power is 11.5 KW. Seamlessly switch between hands-free foot pedal operation and precise hand control (Trigger) for versatile workflows and enhanced safety when handling sensitive batteries.
- Intelligent Thermal Protection: Built-in safety monitors battery temperature (Cont), automatically halting welding (Trigger disable) and alerting you if overheating is detected, preventing damage. If there is no operation for 8 minutes, the spot welder will automatically shut down.
- Ultra-Low Power Consumption: Engineered for exceptional energy efficiency , significantly extending standby time between uses and reducing operational costs. Precision 100-Level Power Control: Fine-tune welding strength for delicate tasks (like phone/Button batteries) or robust jobs (cylindrical power cells) with our intuitive rotary knob.
- Multi-Mode Welding for Diverse Batteries: Expertly weld cylindrical power batteries, mobile phone batteries, and Button batteries (Mode) with tailored settings accessible via the clear control panel.
- Simple Rotary Knob Operation & Clear Interface: Effortlessly adjust settings (Gear, Trigger Time, Mode, Number of continuous spot welds) using the large rotary knob and clearly labeled control panel for ultimate user-friendliness.
| Example | Power approach | What the source establishes |
|---|---|---|
| ZEVA project, Ian Hooper (2012) | Capacitor discharge | The historical build uses six 650 F, 2.7 V ultracapacitors in series, described as 108 F at up to about 16 V. These are that project’s component choices, not recommended specifications for a new build. |
| KaeptnBalu Arduino_Spot_Welder_V3 project | 12 V car battery as the welding-current supply | The repository describes that project’s power source and discusses nickel-strip thickness. These are project claims, not independent test results or a guarantee for another setup. View the project repository. |
The two examples use distinct architectures. Neither demonstrates that a battery charger can substitute for its power source, and their component details should not be copied as a universal design.
What the K100 manual says about materials
The KEKK K100 manual lists nickel-plated sheet thickness of 0.05–0.3 mm and pure nickel sheet thickness of 0.05–0.15 mm. Those are ranges stated for that kit in the surfaced manual, not independently verified performance limits or general guidance for other welders. Check the manual for the exact board and accessories you are considering rather than assuming another project supports the same material.
Recommended Free Tools
Rank #3
- Fully Cordless: Say goodbye to tangled power cords—grab this spot welder and work anytime, anywhere; Note: For optimal performance, fully charge it to 100% before first use; If the product is left unused, please charge it monthly to preserve battery health
- Strong Welding Capacity: With a maximum output power of 3360W, the mini spot welder stands out among handheld models; tested to weld nickel-plated sheets up to 0.2mm thick or pure nickel sheets up to 0.15mm thick (Welding quality closely links to battery charge level)
- Visual Display Screen: An intuitive display greatly boosts convenience, letting you monitor the welding process, device temperature, and remaining battery at all times
- Precise Gear Adjustment: With 99 fine-adjustment gears available, the spot welding equipment perfectly meets your diverse welding needs for different materials and thicknesses
- Auto/Manual Dual Modes: Choose freely between auto welding and manual trigger welding based on your needs—adapts to various scenarios for greater convenience
Electrical safety context—and its limits
OSHA’s 29 CFR 1910.254 addresses arc welding and cutting, including equipment selection and installation, enclosure of controls and input terminals, protection of welding-lead terminals, grounding, and supply connections. It is not a specific evaluation or certification of a DIY battery spot welder or charger conversion, so it cannot establish that such a conversion is compliant or prohibited.
Likewise, OSHA’s March 12, 1996 interpretation on grounding battery chargers concerns charger grounding under specified workplace conditions and use within the conditions assigned by an NRTL approval. It does not assess converting a charger into a welder.
Quick Recap
Best Value
- 5 Minute Quick Start Spot Welder: We use a wide voltage input of 100-240V and an adapter of 15amp high current for fast charging Connect the spot welding machine to the power supply using our adapter, and quickly reach the spot welding mark within 5 minutes (the display screen shows OK for spot welding), which can be used anywhere in the world
- 3-in-1 Mode: Our spot welder has an automatic mode and a manual mode, as well as a foot pedal mode. The automatic mode is where you adjust to the proper setting, insert the spot welder and start working immediately. Manual mode is to adjust to the manual mode, press the button on the spot welding pen will output once. Foot Mode, when you use the foot pedal, the positioning of the soldering probe is much easier. It is very convenient to step on the foot pedal and the spot weld pen will output a signal once
- Wide Application Range: A well made, compact spot welder. Not only for battery pack work, such as cylindrical batteries such as 18650/14500/21700, but even LiFePO4 batteries, industrial batteries, etc. And it can also be used for spot welding of different materials, for example, such as nickel plated sheet, stainless steel sheet, iron sheet, 0.2 nickel-plated and 0.2 nickel-plated butt-welded to achieve a material thickness of 0.4mm. There are 99 adjustable gears, with different gear requirements for different materials
- Professional Battery Spot Welder: Equipped with built-in super energy storage capacitors, Ultra capacitors have many thoughts of cycle life, and the maximum pulse welding power can reach 10KW. It is a brand new MOS, with no interference to the circuit or tripping issues, stable and sustainable operation, making it the best choice for professionals and DIY enthusiasts. But please, you must use it by connecting it to the wall power and charging it while using it, because the Faraday capacitor stores very little electricity and will be consumed within a minute or two
- Product design: The exterior design is rounded with no corners, so it won't hurt when a body part touches it. The shell is made of aluminum alloy, comfortable to the touch, beautiful appearance, not easy to scratch, but also has a flame-retardant nature, very safe
Rank #4
- Wireless, Portable Design: Built-in battery supports cordless operation and easy portability, eliminating cable constraints and enabling flexible use anytime, anywhere
- Visual Display Screen: Real-time voltage, gear settings and welding mode are clearly displayed, simplifying operation steps and ensuring accurate adjustments for stable welding effects
- 80 Adjustable Gears: Realizes refined welding power regulation, adapting to nickel sheets of different thicknesses with a maximum welding thickness of 0.2mm for nickel-plated sheets and 0.15mm for pure nickel sheets, meeting diverse welding requirements
- Reusable Cleaning File: Equipped with a reusable file to remove carbon deposits on the welding tip, maintaining stable welding performance and extending the tip's service life
- Durable Aluminum Shell: Boasts a sturdy aluminum shell that enhances texture and durability, resisting wear and tear for long-term reliable use
Safer next steps for a battery-tab project
- Do not infer compatibility from voltage alone. The K100’s listed 9–16 V working voltage does not mean a charger in that range is an acceptable supply; the manual specifically excludes chargers for that board.
- Use documentation for the exact design. Confirm the permitted power source, pulse control, electrode arrangement, materials, and safety provisions in an attributable manual before assembly.
- Compare purpose-built tools on relevant criteria. For a battery spot welder, check power-source compatibility, supported strip material and thickness, pulse control, included electrodes and accessories, enclosure and safeguards, and whether a manual is available.
- Do not treat project examples as instructions. The ZEVA capacitor arrangement and the Arduino project’s car-battery supply describe different builds; neither is a general recipe or a substitute for design-specific safety information.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
