Fnirsi SWM-10: Repair Battery Packs With This Portable Intelligent Spot Welding Machine (Review)

    • by Clemens Valens
    • Reading time: 4 min

    Battery packs have invaded our world with the rise of cordless electric garden tools, electric bicycles, scooters, cars and more. These packs are spot welded with thin metal strips, creating strong, reliable joints without damaging the cells. However, the downside is that replacing a dead cell becomes a challenging task without the proper tools.

    Don't Solder, Weld!

    Anyone who has ever tried to solder a wire or metal strip to a battery knows it's nearly impossible. At best, you get a fragile joint that falls off with the slightest pull; more likely, you'll overheat the battery and risk it exploding. Adhesive tape or even chewing gum often yields better results.

    What you really need for this type of repair job is a spot welding tool, and that's where the Fnirsi SWM-10 comes in. The Fnirsi SWM-10 is a portable spot welding machine, roughly the size of a small multimeter. Designed for building and repairing battery packs, it also doubles as a 5000 mAh USB power bank for those times when you aren't working on batteries.

    welded 4 layers
    The Fnirsi SWM-10 is designed to weld nickel, iron, and stainless steel sheets up to 0.25 mm thick. I tested it, and it works perfectly.

    Unpacking the Fnirsi SWM-10

    The box includes the Fnirsi SWM-10 device, two thick cables (8 AWG, approximately 30 cm long), two spare welding tips, a USB-A-to-C cable, a roll of metal strip (10 mm wide, 0.1 mm thick, likely nickel), and a multilingual manual. Although I didn't unroll the metal strip, by measuring its circumference and estimating the number of windings, it seems to be around 5 meters long.

    fnirsi swm-10 box contents
    This is what is included in the box.

    The SWM-10 has a sleek, all-black design with a black window and three pushbuttons. The two sockets for the welding cables are located in the upper left corner. On the back, there is a foldable stand. The power button is on the top side of the SWM-10, alongside the USB connectors and a reset pinhole.

    Intuitive Display

    After powering on the device, a 1.8” color display presents various values. These are straightforward and include four user-adjustable parameters: preheat time, pulse length, pulse interval, and dots. Additionally, the display provides status information such as battery voltage, temperature, sound on/off, current, and a spot-weld counter. The left/right buttons move the cursor up and down, while the up/down buttons adjust the selected value, highlighted in yellow. A long press on the left/right button opens and closes the settings menu.

    fnirsi swm-10 color display
    Colorful display.

    A short press on the power button opens (and closes) the charge/discharge screen, where you can check the remaining battery energy and monitor the charging progress.

    The manual is concise, explaining the values, parameters, and the functions of the buttons and LEDs. However, it lacks detailed instructions on how to use the device for welding, which I had to figure out on my own. The only guidance provided is to charge the battery before welding and to avoid pressing too hard on the nickel strip for optimal results.

    How Easy Can the Fnirsi SWM-10 Be?

    It turns out that using the Fnirsi SWM-10 is incredibly simple, which likely explains why it’s touted as intelligent. Just place the two tips sequentially on the workpiece (without pressing too hard) and wait for about two seconds. You'll hear a soft clicking sound, indicating the weld is complete. The number of clicks corresponds to the "Dots" value, which ranges from 1 to 5.

    this is how you do it
    This is how you weld. Press lightly and wait a few seconds.

    The default settings worked well for me when welding a nickel strip to a button cell; removing the strip required significant force. For stronger joints, you can increase the pulse length and the number of dots. However, be cautious: higher settings can cause sparks and smoke, potentially burning or damaging the underlying surface. I recommend wearing goggles to protect your eyes. Additionally, exercise caution when handling thin sheet metal, as it's easy to cut yourself.


    The Fnirsi SWM-10 is a must-have for anyone facing a dead cell in a battery pack, unsure how to fix it. Battery pack replacements can be pricey, making this affordable tool a worthwhile investment. Beyond repairs, it enables DIY battery pack assembly and serves various spot welding needs. Plus, it doubles as a handy 5000 mAh power bank—an all-around versatile addition to any toolkit.



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