3S 20A BMS 18650 Lithium Battery Protection Board (11.1V–12.6V)

This 3S 20A Battery Management System (BMS) board is designed for custom 18650 and 21700 lithium-ion battery builds. Covering a nominal 11.1V up to a fully charged 12.6V, it provides essential safety and balancing for DIY power packs suited to FPV ground stations, radio transmitters, goggles, or low-draw long-range fixed-wing aircraft.

Key features

• Safely manages charge and discharge cycles for 3-cell (3S) lithium-ion arrays
• Delivers up to 20A continuous discharge current for sustained low-to-medium loads
• Integrated hardware protection prevents catastrophic overcharging, deep over-discharging, and short circuits
• Compact layout easily heat-shrinks alongside standard 18650 cell configurations

Specifications

• Configuration: 3S
• Voltage Range: 11.1V nominal, 12.6V max
• Continuous Discharge Current: 20A
• Continuous Charge Current: 20A
• Charging Voltage: 12.6V
• Balance Current: 100mA
• Overcharge Detection: 4.25V per cell
• Over-discharge Cut-off: 2.3-3.0V per cell
• Cell Compatibility: 18650, 21700 (3.7V nominal Li-ion)
• Protection Circuitry: Overcharge, over-discharge, over-current, short-circuit, with automatic recovery
• Weight: 4 g

Note: When assembling lithium-ion packs for primary flight power, multirotor peak current spikes can easily exceed 20A. For demanding drone builds, wire the main power lead to bypass the BMS for discharge, relying on the board solely for safe charging and cell balancing.