The 4S 40 A 18650 Lithium Battery Protection Board (BMS) is a high-current battery management solution designed to safely manage four series-connected 18650 Li-ion cells. Built for demanding loads, it provides comprehensive protection against overcharge, over-discharge, overcurrent, and short-circuit conditions while supporting high continuous discharge. This BMS is ideal for power tools, robotics, electric mobility, inverters, and high-power DIY battery packs requiring a 16.8 V lithium configuration.
Core Board Specifications
• BMS Type: 4S lithium battery protection board
• Supported Cells: 4 × 18650 Li-ion (series connection)
• Continuous Discharge Current: Up to 40 A
• Protection Functions: Overcharge, over-discharge, overcurrent, short-circuit
Electrical & Interface
• Nominal Pack Voltage: 14.8 V
• Maximum Charge Voltage: 16.8 V
• Balance Method: Passive cell balancing (during charging)
• Connection Pads: B+, B−, B1, B2, B3, P+, P−
• Supported Chemistry: Li-ion only (not LiFePO₄)
Performance Characteristics
• Supports high-current loads with stable output
• Automatic cutoff during fault conditions
• Improves pack safety and longevity
• Suitable for continuous heavy-duty operation
Physical Characteristics
• Module Type: PCB-mounted BMS board
• Form Factor: Compact, high-current layout
• Copper Traces: Thickened for 40 A handling
• Clearly labeled solder pads for secure wiring
Compatibility
• 4S 18650 Li-ion battery packs
• High-power DC motors and controllers
• Arduino, ESP32, and embedded power systems
• Power tools, inverters, and mobility projects
Key Advantages
• High 40 A current capability
• Robust safety protections for lithium packs
• Compact design for custom enclosures
• Essential for high-power battery builds
Technical Insights
• Use matched cells (same capacity, age, and brand)
• Balancing works during charging only
• Charger must be rated for 4S Li-ion (16.8 V)
• Incorrect wiring can permanently damage the BMS
Applications
• DIY 4S 18650 battery packs
• Power tools and electric equipment
• Robotics and automation systems
• Energy storage and backup power
• High-current embedded projects
Pro Tip
• Connect BMS before the first charge
• Insulate the board to prevent accidental shorts
• Verify individual cell voltages during assembly
• Use thick wires and secure solder joints for high current
Package Includes
• 1 × 4S 40 A 18650 Lithium Battery Protection Board