Lithium Battery Charger Protection Module (BMS) 3S 20A 12.6V
The Lithium Battery Charger Protection Module (BMS) 3S 20A 12.6V is a reliable battery management solution designed to ensure the safe charging and discharging of 3-series lithium-ion (Li-ion) or lithium-polymer (LiPo) battery packs. By integrating overcharge, over-discharge, over-current, and short-circuit protection, it guarantees both safety and extended battery lifespan.
With a rated current of 20A, this BMS module is suitable for medium-power applications such as electric tools, DIY power banks, e-bikes, portable devices, robotics, and solar-powered storage systems. Its compact PCB design makes it easy to integrate into custom battery packs, providing efficiency, reliability, and protection in a small footprint.
How It Works
This 3S BMS monitors each cell within the battery pack. During charging, it ensures that no cell exceeds 4.25V, preventing overcharging damage. During discharging, it cuts off the output once any cell drops below 2.7V, protecting the pack from deep discharge.
The module also continuously monitors current flow. If the load exceeds the 20A rating, the system activates protection to prevent overheating or permanent damage. Once normal conditions are restored, the BMS automatically resets, ensuring smooth operation without manual intervention.
Key Features
Designed for 3S Li-ion/LiPo battery packs (12.6V max)
Supports continuous discharge current up to 20A
Provides overcharge, over-discharge, over-current, and short-circuit protection
Balances cell voltage to maintain battery health
Compact PCB design for easy integration
Automatic recovery after fault conditions
Extends battery pack lifespan by preventing damage
Specifications
| Parameter | Value |
|---|---|
| Battery Type | Li-ion / LiPo (3 cells in series) – |
| Maximum Pack Voltage | 12.6V |
| Rated Discharge Current | 20A |
| Overcharge Protection | ~4.25V ± 0.05V per cell |
| Over-discharge Cutoff | ~2.7V ± 0.05V per cell |
| Overcurrent Protection | 20A (typical) |
| Short-Circuit Protection | Yes |
| Balance Function | Yes (for equalizing cells) |
| Operating Temperature | -20°C to +60°C |
| PCB Size | Approx. 50 × 20 × 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
DIY lithium battery packs
E-bikes and scooters
Portable power banks
Robotics and automation systems
Solar-powered storage systems
Medium-power electronic devices
