6pcs 4S 40A 14.8/16.8V Li-ion Lithium Battery Protection Board PCB BMS with Balance Function High-Current Charger Protection Circuit for 18650 Cells, Compatible with Drill Motor (4S 40A)

Product Name: 4S 16.8V 40A Lithium Battery Protection BoardSpecifications:Charging Voltage: DC 16.8V – 17.8VContinuous Discharge Current: Up to 40A (consider reducing load if cooling is limited)Continuous Charging Current: Up to 20ADimensions: 45mm × 60mm × 4mmBattery Compatibility:Works with lithium cells rated at 3.7V nominal and 4.2V fully charged, including 18650, 26650, and polymer lithium batteries. Supports electric drills up to 170W when used with appropriate high-drain battery configurations.Important Notes:For reliable drill startup, it’s recommended to use either four 10C–20C or eight 5C–10C high-drain cells (common models: VTC4, VTC4A, VTC5A, VTC6). Copper wire with a cross-sectional area of at least 3 mm² is suggested for the main power leads (0V and 12.6V); nickel strips may not handle the high inrush current.Please connect balance wires to the labeled points: 0V, 4.2V, 8.4V, 12.6V, and 16.8V. During soldering, try to avoid touching any components on the board, and take care not to create a short circuit.During initial battery assembly or charging, if any single cell exceeds 4.2V, the onboard “430” resistor will activate to discharge it (stopping around 4.19V). If this resistor becomes noticeably warm, it’s a good idea to check your wiring for possible errors.

• Electrical Specifications: This 4S 16.8V Li-ion Lithium Battery Protection Board BMS supports charging voltage 16.8V–17.8V, peak discharge current 40A (reduce load if cooling is insufficient), peak charging current 20A, and measures 45×60×4mm(1.77″ × 2.36″ × 0.16″)
• Battery Compatibility: Works with 3.7V nominal / 4.2V full-charge lithium cells including 18650, 26650, and polymer types; compatible with electric tools up to 170W when used with appropriate high-drain battery configurations
• Drill Motor Requirements: Successful startup of Drill Motor systems requires either four 10C–20C or eight 5C–10C high-drain cells; standard low-C-rate 18650 batteries cannot provide sufficient inrush current
• Wiring and Installation Guidelines: Connect balance leads to the correct 0V, 4.2V, 8.4V, 12.6V, and 16.8V points as labeled; avoid contact between the soldering iron and board components during installation; when used with drill motors, use copper wire with cross-section ≥3mm²—nickel strips cannot handle the high inrush current
• Protection and Balancing Function: Provides overcharge, over-discharge, overcurrent, and short-circuit protection; if any cell exceeds 4.2V during initial use or charging, the 430 resistor activates to discharge it to approximately 4.19V—excessive heating indicates incorrect wiring