5S 21V 30A/45A BMS Lithium Battery Protection Board with NTC
5S 21V 30A/45A BMS Lithium Battery Protection Board with NTC
5S 18V–21V 30A/45A BMS Lithium Battery Charging Protection Board with NTC & Balance
Protect and extend the life of your lithium battery packs with this high-performance 5S BMS (Battery Management System) Protection Board. Designed for 18V–21V lithium-ion cell configurations, this module delivers reliable overcharge, over-discharge, and overcurrent protection — all in a compact SMD package. Available in 30A and 45A current ratings and sold in packs of 1, 2, or 3 boards.
Key Features
- 5-Series Cell Configuration: Supports 18V–21V (5S) lithium-ion battery packs for power tools, e-bikes, and DIY energy storage projects.
- Dual Current Options: Choose between 30A and 45A continuous discharge ratings to match your specific load requirements.
- NTC Resistor Temperature Protection: Built-in NTC thermistor monitors battery temperature and automatically cuts off current when the board exceeds safe operating limits (0–80°C), preventing thermal runaway.
- Active Cell Balancing: Equalizes voltage across all 5 cells during charging, maximising total capacity and prolonging overall pack lifespan.
- Overcharge & Over-Discharge Protection: Automatically disconnects the circuit when any individual cell reaches its upper or lower voltage threshold.
- Overcurrent & Short-Circuit Protection: Instantaneous cut-off on load short-circuit events, safeguarding both the board and your battery cells.
- SMD Module Design: Compact surface-mount board is easy to integrate into battery enclosures, power tool packs, and custom battery builds.
- Supply Voltage: 21V (5S fully charged state)
- Operating Temperature: 0–80°C
- Package Options: 1 PC, 2 PCS, or 3 PCS — stock up and save.
Ideal Applications
- 18V–21V cordless power tools (drills, saws, grinders)
- DIY lithium battery pack builds and replacements
- E-bike and electric scooter battery management
- Portable power stations and energy storage systems
- RC vehicles and robotics power packs
- Computer and electronics backup power modules
Technical Specifications
| Cell Configuration | 5S (5 Series) |
| Nominal Voltage | 18V (charged: 21V) |
| Continuous Current | 30A / 45A (selectable) |
| Temperature Sensor | NTC Resistor (built-in) |
| Operating Temperature | 0°C – 80°C |
| Package Type | SMD Module |
| Condition | New |
| Country of Origin | Made in Mainland China |
Related Products You May Like
- Electromagnetic Induction Tester – Coil & Circuit Fault Detector
- Air Compressor Pressure Gauge 0-10/0-12/0-25 Bar | DIY Tool
- 360° Bicycle Chain Cleaner Tool | Bike Gear Cleaning Kit
Learn more: ENERGY STAR product efficiency guidance
Frequently Asked Questions
Q: What does the NTC resistor do on this BMS protection board?
A: The NTC (Negative Temperature Coefficient) resistor is a built-in thermistor that continuously monitors the temperature of the BMS board and battery cells. When the temperature rises beyond the safe threshold, the BMS automatically disconnects the circuit to prevent overheating and potential thermal runaway, keeping your battery pack safe during heavy use or charging.
Q: What is the difference between the 30A and 45A versions of this BMS board?
A: The ampere rating refers to the maximum continuous discharge current the board can safely handle. The 30A version suits lighter loads such as smaller power tools or moderate-draw electronics, while the 45A version is designed for higher-demand applications like heavy-duty cordless tools, e-bikes, or high-current DIY battery packs. Choose based on the peak current draw of your specific device.
Q: Can this BMS board be used to replace an existing battery protection board in a cordless power tool?
A: Yes — this 5S BMS module is widely compatible with 18V–21V lithium-ion battery packs commonly found in cordless drills, circular saws, and grinders. Always verify your existing pack's cell count (5S), voltage, and current requirements before installing to ensure compatibility.
Q: Is the cell balancing feature active during charging only, or also during discharge?
A: The balancing function on this BMS board is primarily active during the charging cycle. It equalises the voltage across all five cells as they charge, ensuring each cell reaches the same state of charge and preventing individual cells from being overcharged or undercharged — which significantly extends the overall lifespan of your battery pack.