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.