1.4 series 16.8V 40A lithium battery protection board with auto recovery function; 2. Integrated with 10 imported low internal resistance MOSFETs, supports continuous discharge up to 40A, with 100mA balancing current, suitable for power tools such as electric drills, sprayers, LED lights, and low-power inverters; 3. Designed for lithium batteries with nominal voltage of 3.6V or 3.7V (including 18650, 26650, and polymer lithium batteries), and full charge voltage of 4.2V per cell; 4. Compatible with electric drills having starting current below 80A and power rating under 230W, equipped with balancing charge functionality; 5. Reduces high current heating by 30% and enhances anti-interference performance; Conditions for successful operation: 1. Requires 4 cells with 15C-20C or 8 cells with 10C-15C power-grade batteries (standard 18650 power cells recommended); 2. Connection wires between battery pack and protection board must be as short and thick as possible; 3. During initial battery welding, ensure no load or external device is connected to the output; 4. If startup fails, refer to the product documentation for troubleshooting; Precautions: 1. Use 4 pieces of 10C-20C or 8 pieces of 5C-10C power-grade batteries for reliable electric drill startup (recommended models: SONY VTC4, VTC4A, VTC5A, VTC6); for 0V to 12.6V connections, use copper wire with cross-sectional area of 3mm or larger (nickel strips not allowed); 2. Wire connections must strictly follow the diagram for 0V, 4.2V, 8.4V, 12.6V, and 16.8V points; avoid contact with any components on the board during soldering and prevent intentional short circuits; 3. During initial battery installation or charging, if any single cell exceeds 4.2V, the 430-ohm resistor may heat up and initiate discharge (stops when voltage drops to approximately 4.19V); if the resistor becomes excessively hot, inspect wiring connections immediately;