4S 16.8V 40A Li-Ion Cell BMS Charging Protection Module

Overview: 4S 16.8V 40A Li-Ion Cell BMS

The 4S 16.8V 40A Li-Ion Cell BMS Charging Protection Module is a compact Battery Management System engineered for 4-cell (4S) lithium-ion and lithium-polymer packs. Designed for medium to high power projects, this BMS provides reliable protection, cell balancing, and automatic recovery to keep your pack safe and performing at its best.

Key Specifications

• Pack configuration: 4S (up to 16.8V fully charged)
• Continuous discharge current: 40A
• Peak cutoff current: approximately 50 to 55A
• Overcharge cutoff: ~4.25 ±0.05V per cell
• Over-discharge cutoff: ~2.7 ±0.1V per cell
• Operating temperature: -20°C to +60°C
• Compatibility: works with CC/CV Li-Ion chargers

Protections and How They Work

• Overcharge protection: Stops charging when any cell exceeds about 4.25V to prevent cell damage.
• Over-discharge protection: Cuts output when cell voltage drops below about 2.7V to protect cell longevity.
• Overcurrent protection: Detects high discharge currents and shuts down output if peak currents reach roughly 50 to 55A.
• Short-circuit protection: Instant cutoff to prevent catastrophic failure of the battery pack or load.
• Cell balancing: Passive balancing maintains equal voltages across all four cells for improved capacity utilization and longer service life.
• Automatic recovery: The module can resume normal operation automatically once fault conditions clear, without manual reset in most cases.

Applications

This BMS is suitable for a wide range of projects that require a reliable 4S protection solution:

• DIY 16.8V battery packs and replacement packs
• Electric bikes, scooters, and personal mobility devices
• Robotics, automation, and high-drain actuators
• Solar energy storage and off-grid power systems
• High-power LED lighting and portable power stations
• Inverters and UPS systems

Installation, Compatibility and Best Practices

• Use with CC/CV Li-Ion chargers and ensure correct connection to B-, P-, and B+ terminals as per pack wiring diagram.
• Ensure proper wiring gauge for 40A continuous loads to avoid voltage drop and heating; consider heavier gauge for peak currents.
• Mount on a stable, non-conductive surface and provide ventilation when used in enclosed spaces or high ambient temperature.
• Balance your cells when assembling packs and periodically check cell voltages to ensure effective balancing operation.

Why Choose This 4S 40A BMS

• Reliable protection suite for safe charging and discharging cycles.
• Integrated cell balancing extends battery life and stabilizes pack performance.
• Robust PCB and thermal design for medium to high power projects.
• Automatic fault recovery reduces downtime for many common faults.
• Ideal for makers, engineers, and system integrators building 16.8V battery solutions.

Note: Images are for illustration purposes only.