Lithium Battery Charger Protection Module (BMS) 3S 40A 12.6V
The Lithium Battery Charger Protection Module (BMS) 3S 40A 12.6V is a powerful and reliable protection board designed for 3-cell Li-ion and LiPo battery packs. With its high discharge current rating of 40A, this BMS is suitable for demanding applications such as high-power e-bikes, electric scooters, solar storage systems, robotics, and heavy-duty DIY power banks.
It provides essential safety functions, including overcharge, over-discharge, overcurrent, short-circuit, and cell balancing. By preventing unsafe operating conditions, this module extends the life of the battery pack and ensures consistent performance even under heavy load.
How It Works
The module monitors each cell in the 3S (12.6V max) battery pack individually. If any cell reaches an overcharge threshold (~4.25V), charging is stopped to prevent damage. Similarly, if any cell discharges below ~2.7V, the BMS cuts off the load to avoid deep discharge.
With its 40A rated discharge current, the module supports powerful motors, inverters, and energy-hungry devices. Built-in short-circuit protection immediately disconnects the output during unsafe conditions, while automatic recovery allows the system to return to normal once the fault is cleared. The balancing feature keeps cells equalized, ensuring maximum pack efficiency and lifespan.
Key Features
Supports 3S Li-ion / LiPo packs (12.6V max)
High discharge current: 40A continuous
Full protection: overcharge, over-discharge, overcurrent, short-circuit
Integrated cell balancing for voltage equalization
Automatic recovery after faults
Compact PCB design for versatile integration
Long lifespan and reliable performance
Specifications
| Parameter | Value |
|---|---|
| Battery Type | Li-ion / LiPo (3 cells in series) – |
| Maximum Pack Voltage | 12.6V |
| Rated Discharge Current | 40A |
| Overcharge Protection | ~4.25V ± 0.05V per cell |
| Over-discharge Cutoff | ~2.7V ± 0.05V per cell |
| Overcurrent Protection | 40A (typical) |
| Short-Circuit Protection | Yes |
| Balance Function | Yes (active balancing) |
| Operating Temperature | -20°C to +60°C |
| PCB Size | Approx. 55 × 25 × 3 mm |
Pin Configuration
| Pin/Pad | Label | Description |
|---|---|---|
| B+ | Battery Positive | Connects to the positive terminal of the pack |
| B- | Battery Negative | Connects to the negative terminal of the pack |
| B1 | Cell 1 connection | Between Cell 1 (+) and Cell 2 (-) |
| B2 | Cell 2 connection | Between Cell 2 (+) and Cell 3 (-) |
| P+ | Pack Positive | Output/charge positive terminal |
| P- | Pack Negative | Output/charge negative terminal |
Applications
High-power e-bikes and electric scooters
Solar energy storage systems
Robotics and automation
DIY lithium battery packs
Power inverters and backup power systems
Heavy-duty portable power banks
