The BMT 4S Lithium Battery Charge/Protection Board (40A) is a high-performance Battery Management System (BMS) designed for 4-series lithium-ion and lithium-polymer battery packs, including 18650 and 26650 cells. It provides essential protection functions to ensure safe charging, discharging, and long-term reliability of lithium battery systems.
This module supports a nominal 14.8V (4S) lithium battery configuration with a full charge voltage of 16.8V, making it suitable for high-power applications such as power tools, portable energy systems, backup power banks, and DIY battery packs.
The board includes advanced protection features such as overcharge, over-discharge, overcurrent, short-circuit protection, and automatic recovery, ensuring stable operation even under demanding load conditions. It is capable of handling continuous discharge currents up to 40A, with a high current burst capability depending on cooling conditions.
An optional balancing function helps equalize cell voltage levels, improving battery lifespan and overall pack stability. The compact PCB design allows easy integration into battery assemblies while maintaining strong thermal and electrical performance.
Key Features:
- 4S lithium battery management system (16.8V max charge)
- Supports 18650, 26650, and Li-ion/LiPo cells
- High current capability up to 40A continuous discharge
- Overcharge, over-discharge & overcurrent protection
- Short-circuit protection with auto recovery function
- Cell balancing function for improved battery lifespan
- Suitable for high-power DIY and industrial applications
Specifications:
- Battery Type: 3.6V / 3.7V lithium cells (Li-ion / LiPo)
- Configuration: 4S (4 series cells)
- Charge Voltage: 16.8V - 18.1V
- Continuous Discharge Current: 40A max
- Continuous Charge Current: up to 20A
- Overcharge Protection Voltage: ~4.25V per cell
- Over-discharge Protection Voltage: ~2.5V per cell
- Balance Start Voltage: ~4.2V per cell
- Operating Temperature: -40 C to +85 C
- PCB Dimensions: ~45 × 55 × 3.4 mm (variant dependent)
- Weight: ~9-10 g
- Protection Functions: Overcharge, over-discharge, overcurrent, short circuit, auto recovery
What's in the box
1 x BMT 4S 40A Lithium Battery Protection & BMS Board 16.8V
