4S 40A 18650 Lithium Battery BMS

The 4S 40A 18650 Lithium Battery BMS is a protection board for building four-series lithium-ion battery packs. It supports four 3.6V or 3.7V cells—or four parallel cell groups—connected in series to produce a 14.8V nominal battery pack with a 16.8V fully charged voltage.

The board protects the battery pack against overcharging, excessive discharge, overcurrent and short circuits. Its stated 40A discharge rating makes it suitable for higher-current battery projects, although the safe practical current depends on the cells, wiring, connections, heat dissipation and load conditions.

This BMS is suitable for battery-pack builders, electronics technicians, robotics developers and DIY users across Ghana. DIYGH supplies lithium battery protection boards, 18650 battery accessories and power modules from Kumasi to customers nationwide.

Product Details:
Product Type: Lithium-ion battery BMS protection board
Battery Configuration: 4S
Compatible Cells: 3.6V or 3.7V lithium-ion cells, including 18650 cells
Nominal Battery-Pack Voltage: 14.8V
Maximum Fully Charged Voltage: 16.8V
Rated Discharge Current: Up to 40A under suitable operating conditions
Maximum Charge Current: Up to 20A for common module versions
Battery Arrangement: Four cells or cell groups connected in series
Protection Functions: Overcharge, over-discharge, overcurrent and short-circuit protection

Application:
Suitable for 4S 18650 battery packs, rechargeable tools, robotics projects, portable power systems, LED lighting, small motors, sprayers, battery-powered electronics, DIY energy-storage projects, STEM practicals and custom lithium battery packs.

Important Usage Information:
This BMS is a battery protection board and does not replace a lithium battery charger. Use a suitable 16.8V lithium-ion charger for the completed 4S pack.

Use cells with similar capacity, voltage, internal resistance and condition. Follow the terminal markings and wiring sequence printed on the board carefully. Incorrect wiring or mismatched cells can damage the board, cells or connected equipment.

This model is intended for standard 3.6V/3.7V lithium-ion cells. It should not be used with LiFePO₄ cells unless the board is specifically marked for LiFePO₄ chemistry.