3S BMS

3S 20A Li-ion Lithium Battery Protection Board (BMS) – 11.1V / 12V / 12.6V

Product Description

This 3-series (3S) 12.6V 20A lithium battery protection board is designed to provide reliable charging and discharging protection for lithium battery packs. It features automatic recovery protection and is suitable for lithium-ion and lithium polymer cells with nominal voltages of 3.6V or 3.7V.

Compatibility & Application Scope

• Suitable for 3-series lithium battery packs

• Compatible with:

  • 18650 batteries

  • 26650 batteries

  • Lithium polymer batteries

• Nominal cell voltage: 3.6V / 3.7V

Electrical Specifications

• Charging voltage: 12.6V – 13.0V

• Continuous discharge current (max): 20A

  • Reduce load current if heat dissipation conditions are poor

• Continuous charging current (max): 10A

Versions & Use Conditions

• Standard Edition

  • Suitable for start-up current up to 40A

  • For power drills under 65W

• Plus Version

  • Suitable for start-up current up to 60A

  • For power drills under 100W

Physical Specifications

• Size: 59 × 20 × 3.4 mm

• Weight: 4.3 g

Important Usage Notes

• Requires sufficient battery power for drill start-up:

  • 3 cells rated 15C–20C, or

  • 6 cells rated 10C–15C

  • Not suitable for starting standard low-rate 18650 cells

• Wiring must strictly follow the voltage sequence:

  • 0V / 4.2V / 8.4V / 12.6V

  • Do not intentionally short-circuit

• When using brushed motors under load, a non-polarized capacitor must be connected in parallel across the motor terminals:

  • Voltage rating above 25V

  • Capacitance: 10µF – 100µF

  • This prevents reverse voltage spikes and MOS transistor damage

• For 3-cell series packs, ensure all cells have the same voltage before use

  • Cells with faster voltage drop indicate poor performance and should not be mixed

Battery Matching Recommendation

Do not mix good batteries with poor-performing batteries. Use three cells with similar capacity and internal resistance. Uneven cell combinations significantly reduce performance and reliability.

This protection board is intended for users with appropriate battery matching and wiring practices to ensure safe and stable operation.