4S 40A Li-ion Lithium Battery Charger Cell Module PCB BMS Balance Charging Board for 18650 Li-ion Batteries
The 4S 40A Li-ion Lithium Battery Management System (BMS) is a protection circuit board designed for 4-cell (4S) Lithium-ion or Lithium Polymer (LiPo) battery packs with a nominal voltage of 14.4V–14.8V and a fully charged voltage of 16.8V. It is commonly used for high-drain applications such as electric drills, sprayers, and LED lights, offering continuous discharge up to 40A, enhanced balancing, and auto-recovery.
Description and Key Features
Balanced Charging: The balanced version (often referred to as the upgraded version) ensures each battery cell is charged to the same voltage level to prolong battery life, featuring a 100mA balancing current.
High Power Capacity: Specifically designed with 10 low-internal resistance MOS tubes to handle 40A continuous discharge, making it ideal for powerful cordless drills.
4-Way Protection: Built-in protection against overcharge, over-discharge, short circuit, and over-current.
Auto-Recovery: The BMS automatically recovers from faults like over-discharge or short circuit once the load is removed or when voltage levels stabilize.
Enhanced Features (Upgraded Version): Newer models often feature improved anti-interference, 30% lower heat dissipation, and increased starting power (up to 220W).#
Specifications (Balanced Version)
Battery Configuration: 4-Series (4S), Lithium-ion/Polymer.
Compatible Nominal Voltage: 3.6V / 3.7V per cell (14.4V – 14.8V total).
Charging Voltage: 16.8V to 18.1V DC.
Continuous Discharge Current (Max): 40A (Requires good heat dissipation/heatsink).
Continuous Charge Current (Max): 20A.
Starting Power Capacity: Suitable for drills starting under 80A, power below 135W-220W.
Overcharge Detection Voltage: 4.25V ± 0.025V per cell.
Over-discharge Detection Voltage: 2.50V ± 0.08V per cell.
Balanced Current: 100mA (approx.).
Operating Temperature: -40°C to +85°C.
Dimensions: Approximately 46mm x 60mm x 3.4mm.
Crucial Wiring Instructions
The BMS must be connected strictly according to the wiring diagram to avoid damage to the circuit:
0V (B-): Connect to battery pack negative terminal.
4.2V (B1): Connect to the positive terminal of the 1st battery.
8.4V (B2): Connect to the positive terminal of the 2nd battery.
12.6V (B3): Connect to the positive terminal of the 3rd battery.
16.8V (B+): Connect to the positive terminal of the 4th battery.
P+ / P-: Connect to the charger and load (common port).
Note: The “430” resistor heating during charging indicates the balancing circuit is actively working. If the resistor heats up when not charging, check for incorrect wiring.
Important Usage Notes
High Drain Batteries Required: To start electric drills, you must use high-drain batteries (e.g., 15C-20C). Ordinary 18650 batteries will not work.
Voltage Balancing: Ensure all 4 groups of batteries are at the same voltage before assembly.
Heat Dissipation: For continuous 40A use, a heatsink or enhanced cooling is required to prevent over-temperature protection from shutting down the system.
Motor Protection: When using with brush motors, it is recommended to add a non-polar capacitor (10uF-100uF, >25V) across the motor’s positive and negative terminals to prevent voltage spikes from breaking the MOS tubes.
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