4S 14.8V 16.8V 40A 18650 Lithium Battery BMS Protection Board with Balance

4S 14.8V 16.8V 40A 18650 Lithium Battery BMS Protection Board with Balance is a high-drain 4-series (4S 14.4V/14.8V nominal, 16.8V full charge) Battery Management System (BMS) PCB engineered for high-power 16.8V cordless drills, electric screwdrivers, RC vehicles, and 4S 18650/21700 battery banks. Capable of 40A continuous discharge current (up to 80A pulse for high-inrush motor starts) and equipped with an onboard passive cell-balancing resistor network, it protects and equalizes all 4 cell groups simultaneously.

Key Features:

• High-Power 40A Continuous / 80A Peak Discharge: Populated with a parallel array of ultra-low-$R_R_DS(on) power MOSFETs to handle 40A continuous current and 80A motor-start inrush spikes without nuisance tripping.
• Integrated 4-Channel Passive Cell Balancing: Built-in bleed resistors automatically equalize cell voltages (~35mA–42mA balance current) near 4.20V so all 4 series cell groups reach full charge together.
• 4-Stage Hardware Protection: Monitors `B-`, `B1`, `B2`, `B3`, and `B+` to protect against overcharging (4.25V/cell), over-discharging (2.50V/cell), overcurrent (60A–80A), and short circuits.
• Anti-Interference Cordless Drill Design: Includes filtering capacitors to prevent inductive motor brush noise from falsely triggering overcurrent shutdown on 16.8V drills.
• Low Quiescent Standby Drain (<100µA): Preserves stored energy when tool or solar battery packs sit idle.

Technical Specifications:

• Supported Battery Configuration: 4S (4 Series 3.7V Li-ion / 18650 / 21700 / 26650 Cells — 14.8V Nominal)
• Charging Voltage: 16.8V to 17.0V DC CC/CV
• Continuous Discharge Current: 40A Max (Use High-Drain ≥15C–20C Power Cells for Drill Loads)
• Continuous Charge Current: 20A Max
• Instantaneous / Pulse Current: Up to 80A
• Cell Balancing Current: ~35 mA to 42 mA per channel (at 4.18V–4.20V)
• Overcharge Detection Voltage: 4.25V ± 0.05V per cell
• Over-Discharge Detection Voltage: 2.50V ± 0.10V per cell
• Quiescent Current: < 100 µA | Operating Temp: -40°C to +85°C

Mechanical Specifications:

• PCB Material: Heavy-Copper FR-4 Double-Sided Green Fiberglass PCB
• Terminals: 7 × Wide Tinned Solder Pads (`0V`/`B-`, `3.7V`/`B1`, `7.4V`/`B2`, `11.1V`/`B3`, `14.8V`/`B+`, `+`/`P+`, `-`/`P-`)

Dimensions:

• Length: ~60 mm (Balanced Version)
• Width: ~45 mm
• Thickness: ~4.0 mm
• Weight: ~14 g

Pinout and Wiring:

• 0V (B-): Connect to Cell 1 Negative (Pack Negative).
• 3.7V (B1): Connect between Cell 1+ and Cell 2-.
• 7.4V (B2): Connect between Cell 2+ and Cell 3-.
• 11.1V (B3): Connect between Cell 3+ and Cell 4-.
• 14.8V (B+): Connect to Cell 4 Positive (Pack Positive 14.8V/16.8V).
• + (P+) & – (P-): Connect to 16.8V load and 16.8V CC/CV charger using heavy 12–14 AWG wire (never mix high-drain power cells and old laptop cells in the same pack!).

Datasheet Reference:

• Protection Architecture: 4S Li-Ion BMS Supervisor + 4-Channel Passive Bleed Balancer + 8/10-MOSFET Power Stage

Commonly Used in:

• 16.8V (4S) Cordless Drills, Impact Drivers, and Rotary Saws
• 4S2P / 4S4P 18650 Solar & Portable Power Station Packs
• 14.8V High-Power RC Boats, Rovers, and Robotics
• 12V–16.8V Car Vacuum Cleaners, Air Compressors, and Car Wash Pumps

Applications:

• Builds or repairs 4S1P and 4S2P 16.8V cordless drill battery packs that draw 30A–60A startup current spikes.
• Provides both high-current 40A protection and automatic 4-cell passive balancing on a single compact board.
• Powers 12V–16V portable air compressors, pressure washers, and high-power LED work lights.

Equivalent Models:

• 4S 30A High Current Li-ion Lithium Battery 18650 Charger Protection Board Module: 30A 4S BMS module (`PID 2700`).
• 3S 40A 18650 Lithium Battery Protection Board: 3-cell (11.1V/12.6V) 40A balanced BMS board (`PID 22419`).

Package Includes:

• 1 × 4S 14.8V 16.8V 40A 18650 Lithium Battery BMS Protection Board with Balance