5S 18/21V 20A Li-Ion Cell BMS Charging Protection Module

Overview: 5S 18/21V 20A Li-Ion Cell BMS

The 5S 18/21V 20A Li-Ion Cell BMS (Battery Management System) is a compact, high-performance protection module designed to safeguard 5-series lithium-ion battery packs. Engineered for applications that demand reliable charge and discharge safety, this BMS delivers precise voltage monitoring, multi-level protections, and balanced charging to maximize pack life and performance.

Why Choose This 5S Li-Ion BMS?

• Engineered specifically for 5S (5-cell) Li-Ion packs: nominal 18.5V (3.7V per cell) with a maximum charge voltage around 21V.
• 20A discharge capability supports medium- to high-power devices like e-bikes, power tools, and robotics.
• Robust protection set: overcharge, over-discharge, overcurrent, and short-circuit safety to protect cells and connected electronics.
• Balanced charging helps equalize cell voltages and extend overall battery lifespan.

Key Features

• Designed for 5S Li-Ion battery packs (5 × 3.7V cells = 18.5V nominal)
• 20A continuous discharge capacity suitable for demanding loads
• Multi-level protection: overcharge, over-discharge, overcurrent, and short-circuit
• High-quality MOSFETs and integrated control IC for efficient switching and thermal stability
• Balanced charging function to improve long-term cell health
• Compact form factor for easy integration into DIY and OEM battery packs

Typical Applications

• E-bike and electric scooter battery packs
• Portable power tools and cordless equipment
• DIY power banks and custom battery packs
• Robotics and hobby electronics requiring 18–21V supply
• Solar energy storage and portable solar battery solutions

Technical Specifications

• Battery configuration: 5S Li-Ion (5 cells in series)
• Nominal voltage: 18.5V (3.7V per cell)
• Maximum charge voltage: up to 21V (typical cell charge 4.2V × 5)
• Continuous discharge current: 20A
• Protections: overcharge, over-discharge, overcurrent, short-circuit
• Balanced charging: passive balance function across cells
• Components: high-quality MOSFETs and control IC for reliability

Wiring and Installation Notes

Correct wiring is essential to the safe operation of the BMS. Follow these guidelines:

• Terminals: connect cells and pack leads to the labeled terminals B+, B-, B1, B2, B3, B4, B5 in order.
• Polarity: ensure correct polarity on every connection. Reversed wiring can permanently damage the module.
• Wiring: use appropriately rated, high-quality wires for both load and charging connections to handle 20A continuous current.
• Fusing: consider adding a fuse or circuit breaker on the main pack positive lead for additional safety.
• Placement: mount the BMS where it has adequate ventilation and is protected from moisture, dust, and direct mechanical stress.

Installation Checklist

1. Verify each cell voltage and state before connecting the BMS.
2. Connect cell taps in order: B- (pack negative), B1 (cell1 positive), B2 (cell2 positive), B3, B4, B5, and B+ (pack positive).
3. Secure all connections and insulate exposed terminals to prevent shorts.
4. Test pack voltage and balance behavior with a multimeter before first use.
5. Charge the pack under supervision for the first cycle to confirm protections engage correctly.

Safety and Best Practices

• Always follow Li-Ion battery safety guidelines: avoid over-temperature, physical damage, and deep discharge.
• Do not exceed the rated continuous current of 20A. For intermittent higher currents, confirm MOSFET and PCB trace ratings and check thermal performance.
• Keep the BMS away from conductive debris and liquids. Use heat shrink or an enclosure for added protection when used in mobile applications.
• If any abnormal heating, swelling, or strange odors occur, disconnect the pack immediately and inspect cells and wiring.

Support and Compatibility

This 5S 18/21V 20A Li-Ion BMS is compatible with most 5-cell Li-Ion chemistries used in e-bikes, power tools, robotics, and DIY battery projects. For specific compatibility questions or custom wiring advice, consult our technical support or an experienced battery technician.

Summary

The 5S 18/21V 20A Li-Ion Cell BMS Charging Protection Module provides reliable, balanced protection for 5S battery packs. With multi-level safety, 20A discharge capacity, and high-quality components, it is an excellent choice for hobbyists and professionals building e-bikes, power tool packs, solar storage, and other portable power systems.