This portable spot welder is designed for DIY enthusiasts and professionals. Its compact design features an integrated power supply and welding pen, eliminating the need for external components. The welding pen uses gold-plated terminals for excellent conductivity and low contact resistance. It includes a micro-USB 5V charging interface for convenient recharging. Built with precision craftsmanship and high-performance components, it offers ease of use and long service life.Operation instructions: 1. Press and hold the power button for 3 seconds to turn the device on or off. 2. After startup, the unit operates in automatic welding mode, delivering one weld every 2 seconds. 3. Press the power button to adjust output power level; blue LED indicates selected gear. 4. Ensure battery surfaces are clean, rust-free, and smooth before welding. 5. Ensure nickel strips are clean and smooth. 6. The welding tip must make firm metal-to-metal contact to initiate a weld; lifting the tip allows the next weld cycle. 7. Apply appropriate pressure so the welding needle, nickel strip, and battery surface maintain solid contact—avoid poor or intermittent contact. For different nickel thicknesses, select the appropriate power gear. Higher power is not always better; test to determine the optimal setting.Model: SW-401 Charging: Micro-USB 5V Battery: Compatible with 18650 or 21700 lithium-ion batteries Warning: Do not touch any exposed metal parts of the device with the welding pen. Color: Black Material: Aluminum alloy Dimensions: Approx. 249.7 × 57.83 × 24.45 mm (9.84 × 2.27 × 0.96 in) Package Includes: 1 × Spot Welder Machine Note: Only the item listed is included; accessories shown are for illustration only. Note: Color may vary slightly due to screen settings and lighting conditions.