Charge/Discharge Protection Module BMS 4S – 4 × 18650 Li-Ion Batteries 40A
The 4S 40A BMS module provides complete protection for 18650 Li-Ion battery packs composed of 4 cells in series (14.8V). It is ideal for applications such as drills, electric screwdrivers, drones, robot vacuums, RC cars, or other devices powered by 14.8V battery packs.
Functions and Advantages
- Protection against overcharge and over-discharge
- Discharge current limiting (40A continuous, 70A instant)
- Protection against short circuit and overcurrent
- Active balancing function between cells – uniform charging
- Individual controller for each cell
- High performance and reliability for demanding applications
Operation
Each cell is monitored independently. When the voltage difference between cells exceeds 0.1V, the current of the most charged cell is redirected through a resistor, balancing the entire pack. This ensures all cells reach 4.2V simultaneously during charging and 3.2V during discharge, extending battery life.
Technical Specifications BMS 4S 40A
Input Voltage | 16.8V – 18.1V DC |
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Maximum Charging Current | 20A (continuous) |
Maximum Discharge Current | 40A (continuous), 70A (instant) |
Maximum Voltage per Cell | 4.2V ± 0.03V |
Minimum Voltage per Cell | 3.2V ± 0.1V |
Number of MOSFETs | 10 |
Balancing Current | 100 mA at 4.2V |
Integrated Protections | short circuit, overcurrent, balancing |
Dimensions | 60 × 45 × 3.4 mm |
Recommended Applications
- Electric screwdrivers and drills
- Robot vacuums, drones
- RC cars, hoverboards
- DIY projects with 14.8V Li-Ion batteries
Photo Gallery – BMS 4S 40A Module






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