3S 40A 18650 Lithium Battery Charger Protection Board BMS (11.1V - 12.6V) with Balance Function for Drill Motor & LiPo Cells

Safely power high-drain power tools and motor projects with the 3S 40A 18650 Lithium Battery Protection Board (BMS) with active cell balancing. Engineered specifically for 3-series ( $11.1 ext{V}$ nominal / $12.6 ext{V}$ peak) Li-ion and LiPo battery packs, this heavy-duty BMS handles up to $40 ext{A}$ continuous discharge current and high peak surge currents, making it ideal for cordless drill motors, electric screwdrivers, and robotics. Built with multi-layer circuit protection including overcharge, over-discharge, overcurrent, and short-circuit protection, as well as integrated cell balance circuitry to maximize battery pack lifespan and capacity.

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Tags 3S 40A BMS 3S 18650 Battery Protection Board 3S BMS with Balance 12.6V Drill Motor BMS 3S 40A Balanced BMS Module 11.1V 12.6V Lithium Battery BMS Cordless Drill Battery Protection Board

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Product Details :

The 3S 40A 18650 Lithium Battery Protection Board (Enhanced Balanced Version) is an industrial-grade Battery Management System (BMS) designed for $3 ext{-cell}$ ( $3 ext{S}$ ) series-connected Li-ion or LiPo battery configurations. Operating across the nominal voltage range of $11.1 ext{V}$ ( $3.7 ext{V}$ per cell) to $12.6 ext{V}$ fully charged ( $4.2 ext{V}$ per cell), this module is specifically tuned to withstand the intense current spikes and inductive back-EMF generated by high-power DC motors, such as those in cordless drills, lawn trimmers, and DIY electric vehicles.

Featuring built-in passive cell balancing circuitry, the module equalizes the voltage across all three series cells during the end of the charge cycle ( $100 ext{mA}$ balance current). This prevents individual cells from overcharging or undercharging relative to others, significantly extending overall battery pack health and usable capacity. Equipped with low internal resistance power MOSFETs, the board sustains up to $40 ext{A}$ continuous discharge while providing instant short-circuit cutoff and thermal overload defense.

Key Features and Benefits

High Discharge Current Rating ( $40 ext{A}$ Max Continuous): Designed with low-resistance MOSFET array capable of handling inductive motor startup currents ( $up to 80 ext{A}$ transient surge).
Integrated Cell Balancing Function: Automatically balances voltage differences across individual cells during charging ( $100 ext{mA}$ balance current per cell).
Comprehensive 4-Fold Safety Protection: Built-in protection against overcharge, over-discharge, overcurrent, and output short circuits.
Optimized for Cordless Drill Upgrades: Engineered to handle motor stall currents and high starting torque in power tools without premature tripping.
Heavy Copper PCB Traces: Multi-layer thick copper pads minimize electrical resistance, ensuring cool running during sustained heavy loads.

Technical Specifications

Feature Component	Specification Details
Series Cell Configuration	$3 ext{S}$ ( $3 ext{ Series}$ Li-ion / LiPo cells, e.g., 18650, 26650)
Nominal Voltage Rating	$11.1 ext{V} - 11.5 ext{V DC}$
Full Charge Cutoff Voltage	$12.6 ext{V DC}$ ( $4.2 ext{V} pm 0.05 ext{V}$ per cell)
Continuous Discharge Current	Up to $40 ext{A}$ (requires good heat dissipation)
Continuous Charge Current	Up to $20 ext{A}$
Overcharge Detection Voltage	$4.25 ext{V} pm 0.05 ext{V}$ per cell
Over-discharge Detection Voltage	$2.50 ext{V} pm 0.08 ext{V}$ per cell
Cell Balancing Current	$pprox 100 ext{mA}$ per cell
Internal Resistance	$< 10 ext{ m}Omega$
Operating Temperature	$-40^circ ext{C to } +80^circ ext{C}$

Wiring & Connection Guide

1. Solder Pad Mapping:

Pad Label	Connection Point	Wire Gauge Recommendation
0V ( $B_-$ )	Negative terminal of Cell 1 (Pack Main Negative)	Thick Silicone Wire ( $12 - 14 ext{ AWG}$ )
4.2V ( $B_1$ )	Positive terminal of Cell 1 / Negative of Cell 2	Standard Wire ( $20 - 22 ext{ AWG}$ )
8.4V ( $B_2$ )	Positive terminal of Cell 2 / Negative of Cell 3	Standard Wire ( $20 - 22 ext{ AWG}$ )
12.6V ( $B_+$ )	Positive terminal of Cell 3 (Pack Main Positive)	Thick Silicone Wire ( $12 - 14 ext{ AWG}$ )
$P_+$ / $C_+$	Positive output to load / Positive input from charger	Thick Silicone Wire ( $12 - 14 ext{ AWG}$ )
$P_-$ / $C_-$	Negative output to load / Negative input from charger	Thick Silicone Wire ( $12 - 14 ext{ AWG}$ )

2. Wiring Diagram Schematic:

          [Cell 3]             [Cell 2]             [Cell 1]
     (+) ---|||--- (-)    (+) ---|||--- (-)    (+) ---|||--- (-)
      |            |       |            |       |            |
      |            +---+---+            +---+---+            |
      |                |                    |                |
      v                v                    v                v
   +------+----------+------+-------------+------+----------+------+
   | 12.6V(B+)      8.4V(B2)             4.2V(B1)         0V(B-)   |
   |                                                               |
   |              3S 40A BALANCED BMS PROTECTION BOARD             |
   |                                                               |
   |     P+ / C+                                      P- / C-      |
   +--------+--------------------------------------------+---------+
            |                                            |
            v                                            v
     [ Load / Charger (+) ]                       [ Load / Charger (-) ]

IMPORTANT DRILL MOTOR NOTE: To start a heavy inductive motor (such as a 775 motor or power drill) without triggering BMS current trip protection, use high-drain discharge batteries (minimum $15 ext{A} - 20 ext{A}$ rating per cell) and keep battery connection wires as short and thick as possible ( $12 - 14 ext{ AWG}$ ).

Applications

Cordless Drill & Power Tool Repair: Converting old Ni-Cd/Ni-MH power tools to $12 ext{V}$ 18650 Lithium-ion packs.
High-Torque DC Motor Drives: Powering 775/795 DC motors in robotics, DIY CNCs, and electric sprayers.
Custom 12V Li-ion Battery Packs: Building portable $12 ext{V}$ power banks for LED lights, solar storage, and Bluetooth amplifiers.
RC Models & Drones: Protecting $3 ext{S}$ battery packs used in RC boats, starter kits, and ground vehicles.