Independent doublespring mechanism: Each welding needle extends and retracts independently, with balanced pressure to prevent loose welds and improve throughput in batch spot welding. This design addresses the pressure imbalance of single integrated pens and is suited for volume production. Efficient welding tool for 18650 batteries: Handheld spot welder optimized for 18650 cell packs, featuring a builtin switch and an automatic trigger for precise, easy operation. Compatibility and usage: This is an integrated spot welding pen that must be connected to a spot welding machine; it cannot be used on its own. Ergonomic onehanded operation: Builtin travel switch enables onehanded use without a foot pedal, improving work efficiency. The penstyle grip allows the operator's hand to rest comfortably, enabling a large contact area on the battery during welding. The long stroke and balanced handle help reduce fatigue during extended use, making it well suited for batch production. Practical use scenarios: Assembly of 18650 battery packs for consumer electronics, power tools, or electric vehicles in batch production lines. Prototyping and work where quick, repeated spot welds on battery cells are required. Small to midscale manufacturing or workshop settings that require efficient, onehanded operation for continuous welding tasks.