FMA 5S 18V Li-ion Battery Protection Circuit Board (BMS/PCM)
Professional-grade Battery Management System (BMS) protection circuit board designed for 5S lithium-ion and lithium-polymer battery packs. Provides comprehensive protection against overcharge, over-discharge, overcurrent, and short circuit conditions to ensure safe and reliable battery operation for various applications.
Key Features
- 5S Configuration: Designed for 5-cell series lithium battery packs (18V nominal, 18.5V typical)
- Multi-Protection: Overcharge, over-discharge, overcurrent, and short circuit protection
- 5A Continuous Current: Supports up to 5A continuous discharge current
- Compact Design: Space-efficient PCB layout ideal for smaller battery packs
- High Reliability: Quality components ensure long-term stable operation
- Versatile Applications: Suitable for portable devices, small power tools, and custom battery projects
Package Contents
- 1× FMA 5S BMS Protection Circuit Board
Technical Specifications
| Configuration | 5S (5 cells in series) |
| Nominal Voltage | 18V (3.6V per cell) |
| Typical Voltage | 18.5V (3.7V per cell) |
| Full Charge Voltage | 21V (4.2V per cell) |
| Max Continuous Discharge Current | 5A |
| Overcharge Protection Voltage | 4.25V ± 0.05V per cell |
| Over-discharge Protection Voltage | 2.5V ± 0.1V per cell |
| Battery Chemistry | Li-ion / LiPo |
| Weight | Approximately 100g |
| Condition | Brand New |
Applications
- 5S lithium-ion battery pack protection
- 18V power tool battery replacements
- Portable power banks and battery packs
- Small power tool battery assemblies
- LED lighting systems
- Portable electronic devices
- RC hobby applications
- Medical equipment battery packs
- Custom battery pack projects
- DIY battery rebuilds and upgrades
Protection Functions
Overcharge Protection: Automatically disconnects charging when any cell reaches the overcharge protection voltage (4.25V ± 0.05V), preventing battery damage from excessive voltage.
Over-discharge Protection: Cuts off discharge when any cell voltage drops to the protection threshold (2.5V ± 0.1V), preventing deep discharge that can permanently damage lithium cells.
Overcurrent Protection: Monitors discharge current and disconnects the load if current exceeds safe limits (5A continuous), protecting both the battery and connected devices.
Short Circuit Protection: Instantly disconnects the battery in the event of a short circuit, preventing fire hazards and equipment damage.
Installation & Wiring
Before Installation:
- Ensure all battery cells are balanced and at similar voltage levels (within 0.1V)
- Verify that the battery pack voltage matches the BMS specification (5S configuration)
- Prepare necessary tools: soldering iron, wire strippers, multimeter, heat-shrink tubing
- Work in a clean, well-ventilated area with proper ESD protection
- Wear safety glasses and insulated gloves
Wiring Guidelines:
- Connect balance wires to each cell in the correct sequence (B0 to B5, refer to product images)
- Use appropriate wire gauge for main power connections (minimum 18AWG for 5A)
- Double-check polarity before making final connections (positive to P+, negative to P-)
- Ensure all solder joints are clean and secure with good electrical contact
- Insulate all connections with heat-shrink tubing to prevent shorts
- Test voltage at each balance point with a multimeter before powering on
- Verify total pack voltage is within expected range (18V-21V)
Required Skills:
- Understanding of lithium battery chemistry and safety
- Proficiency in soldering and electrical connections
- Ability to read wiring diagrams and follow technical specifications
- Knowledge of proper battery handling and safety protocols
- Experience with multimeter usage and voltage testing
Who Should NOT Attempt Installation:
- Individuals without electrical or electronics experience
- Those unfamiliar with lithium battery safety requirements
- Anyone without proper tools or workspace
- Minors without qualified adult supervision
- If unsure about any aspect of installation, consult a professional technician
Important Notes
Current Rating: This BMS is rated for 5A continuous discharge current. Ensure your application does not exceed this current limit. For higher current applications, consider our 7S, 10S, or 12S BMS boards with higher current ratings.
18V Power Tool Compatibility: This 5S BMS is ideal for 18V power tool battery pack replacements and rebuilds. The 18V nominal voltage is a common standard for cordless power tools.
Connector Customization: We ship the standard configuration as shown in the main product images. If you require specific connectors or custom wire arrangements, please refer to the product gallery images and contact us with your requirements before ordering.
Compatibility: This BMS is designed for 5S lithium-ion or lithium-polymer battery packs with nominal voltage of 18V/18.5V. Ensure your battery configuration matches before purchase. Using this BMS with incorrect battery configurations can result in improper protection and potential safety hazards.
Testing: After installation, perform thorough testing including voltage checks at all balance points, charge/discharge cycles, and protection function verification before putting the battery pack into regular use.
Why Choose FMA BMS Products?
FMA specializes in high-quality battery management solutions for lithium-ion and lithium-polymer battery systems. Our BMS boards are manufactured using premium components and undergo rigorous quality control testing to ensure reliable protection and long service life. Each board is inspected and tested before shipment to guarantee it meets our strict quality standards.
Custom BMS Solutions
Need a different cell configuration, current rating, or custom features? We offer custom BMS design and manufacturing services. Contact us with your specifications including cell count, voltage requirements, current ratings, and any special features you need, and we'll create a tailored solution for your application.
Safety Information
Charging: Use only chargers designed for 5S lithium battery packs with proper voltage (21V) and current specifications. Never exceed the maximum charging voltage.
Storage: Store in a cool, dry place away from direct sunlight, heat sources, and flammable materials. Keep out of reach of children.
Operation: Do not bypass or disable protection functions. Do not expose to water, moisture, or conductive materials that could cause short circuits.
Temperature: Operate within recommended temperature range. Avoid extreme temperatures during charging and discharging.
Disposal: Dispose of according to local regulations for electronic waste. Do not incinerate or dispose of in regular trash.
Inspection: Regularly inspect for signs of damage, overheating, or component failure. Discontinue use immediately if any abnormalities are detected.
Shipping & Transportation Notice
Hazardous Material: This product is designed for use with lithium batteries and may be subject to shipping restrictions.
Air Transport Restrictions: Due to international air transport regulations, shipments may be subject to additional restrictions and longer transit times.
Packaging Compliance: All shipments comply with applicable packaging requirements for electronic components.
Delivery Time: Electronic component parcels may experience extended delivery times due to customs inspections and carrier handling procedures.
Documentation: Proper documentation accompanies all shipments to ensure compliance with international shipping regulations.