3S 20A 12V 18650 Lithium Battery Charger Board Protection Module BMS

he 3S 20A 18650 Lithium Battery Charger Protection Module (BMS) is a high-performance battery management system designed for safe and efficient operation of 3-series lithium-ion battery packs. This module protects your batteries from overcharge, over-discharge, overcurrent, and short circuits—extending battery life while maintaining optimal performance.

Capable of handling up to 20A of continuous discharge current, this BMS is suitable for moderate to high-power applications, including e-bikes, power banks, DIY solar energy storage systems, portable electronics, and robotics. The board automatically balances the cells during charging, helping to maintain uniform voltage across all 3 cells and prevent capacity loss over time.

With built-in precision ICs and MOSFETs, the module delivers stable performance under various load conditions. Its compact form factor and easy-to-solder terminals make it ideal for DIYers and professional developers alike.

Designed for 3S (3 cells in series) lithium-ion or LiPo battery configurations, it supports 12.6V charging systems and works with 18650 and other compatible lithium battery types.

📐 Specifications – 3S 20A BMS Module

• Battery Configuration: 3S (3 cells in series)

• Nominal Battery Voltage: 11.1V (3.7V x 3)

• Full Charge Voltage: 12.6V (4.2V x 3)

• Continuous Discharge Current: 20A

• Charging Voltage: 12.6V

• Overcharge Protection Voltage: 4.25V ± 0.05V per cell

• Over-discharge Protection Voltage: 2.5V ± 0.05V per cell

• Overcurrent Protection: 25A ± 1A

• Short Circuit Protection: Yes

• Cell Balancing Function: Yes

• Dimensions: Approx. 56mm x 45mm x 4mm

• Application: 18650 lithium-ion battery packs, e-bikes, tools, solar storage, RC projects

🔌 How to Connect

• B+ → Connect to battery pack positive terminal

• B- → Connect to battery pack negative terminal

• B1, B2 → Connect between cells (B1 = Cell 1+, B2 = Cell 2+)

• P+ / P- → Connect to charger/load positive/negative

• Note: Use thick wires for high current paths. Always connect batteries before applying any charging or load.

⚠️ Important Usage Tips

• Ensure battery cells are matched in voltage, capacity, and type before connecting.

• Always connect the batteries in series first, then connect the BMS wires in the correct order (B-, B1, B2, B3).

• Do not reverse polarity—this may damage the BMS.

• Use a 12.6V lithium charger for proper charging.

• The BMS does not include a charging circuit — it only protects and balances the pack.