3S 40A 18650 Lithium Battery BMS Protection Board – 11.1V / 12.6V with Auto Recovery & Cell Balancing
The 3S 40A 18650 Lithium Battery Protection Board is a high-performance Battery Management System (BMS) designed to protect and manage 3-cell series lithium-ion battery packs. Rated at 11.1V nominal and 12.6V fully charged, this BMS board is purpose-built for demanding applications such as cordless electric drills, garden sprayers, LED lighting systems, and low-power inverters where both high discharge current and precise cell protection are critical.
Built for High-Current Power Tools
This BMS module delivers a continuous discharge current of up to 40A, with a maximum supported starting current of 80A — making it directly compatible with drill motors drawing up to 135W of power. The continuous charge current is rated at 20A, enabling fast recharging without overloading the protection circuitry. For environments where cooling is limited, it is advisable to operate at a reduced load to maintain long-term board integrity.
Active Cell Balancing for Longer Battery Life
One of the standout features of this board is its built-in 100mA active cell balancing, which ensures each of the three cells in the pack remains at an equal state of charge during both charging and discharging cycles. This balancing action prevents individual cell overstress, significantly prolonging the overall lifespan of the battery pack. Combined with the AUTO Recovery function, the board automatically resets after a protection event — removing the need for manual reset switches or user intervention.
Comprehensive Multi-Layer Protection
The board integrates 10 low on-resistance MOS tubes that provide a full suite of protections including overcharge detection (4.25V ±0.025V per cell), over-discharge detection (2.50V ±0.08V per cell), and overcurrent protection rated at 40A. The wide operating temperature range of -40°C to +85°C ensures reliable performance in both hot workshop conditions and cold outdoor environments.
Wide Cell Compatibility
This BMS is compatible with any 3.6V or 3.7V nominal lithium-ion cell format, including the popular 18650 and 26650 cylindrical cells, as well as flat polymer lithium (LiPo) cells. The charging voltage range of 16.8V to 18.1V covers standard 3S lithium charger outputs, making integration straightforward.
Compact and Easy to Install
With a compact PCB footprint of just 46 × 60 × 3.4 mm, this protection board is designed to sit neatly within battery packs or directly on the battery bundle itself — ideal for space-constrained drill bodies and portable power tool enclosures. Its lightweight construction adds minimal weight to the overall assembly.
Whether you are building a custom 3S 18650 battery pack for a cordless power tool, replacing a damaged BMS in an existing pack, or designing a DIY lithium battery solution, this 3S 40A BMS protection board delivers the protection, balance, and current handling needed for a safe and high-performing build.
Package contains
1 x 3s 40A bms with balance
