3S 40A 12.6V BMS Li-ion Lithium Battery Protection Board (Enhanced Version)
Overview
The 3S 40A BMS is a high-performance battery management system designed for 12.6V Lithium-ion packs. It provides essential protection for 3-series battery configurations (18650/26650 cells), ensuring safety during charging and discharging. This module is specifically built to handle high-current demands, making it the perfect choice for high-power DIY projects and electric tool repairs.
Key Features
High-Current Support: Supports continuous discharge up to 40A and charging up to 20A.
Full Protection Suite: Built-in protection against overcharge, over-discharge, over-current, and short circuits.
Efficient Design: Utilizes 10 low-resistance MOSFETs to minimize heat and maximize power delivery.
Automatic Recovery: Automatically restores output once the fault condition is removed.
Technical Specifications
| Feature | Specification |
| Series Configuration | 3S (3 Cells in Series) |
| Nominal Voltage | 11.1V / 12V |
| Charging Voltage | 12.6V – 13.6V |
| Continuous Discharge Current | 40A (Max) |
| Peak Starting Current | 80A (Instantaneous) |
| Dimensions | 41mm x 60mm |
Common Applications
Power Tool Repairs: Ideal for upgrading or repairing 12V cordless drills (e.g., DeWalt, Makita, Bosch).
DIY 12V Battery Packs: Build custom battery packs for LED strips, WiFi routers, and DC fans.
Solar Energy Storage: Manage small-scale solar battery storage for emergency backup lighting.
Robotics: Power high-torque DC motors in mobile robot platforms.
Important Installation Guide
For successful operation, ensure you follow the wiring sequence below:
Connect the B- (0V) battery terminal.
Connect the B1 (4.2V) terminal.
Connect the B2 (8.4V) terminal.
Finally, connect the B+ (12.6V) terminal.
Note: Using high-drain “Power Cells” is highly recommended when using this BMS for electric motors or drills.

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