5S BMS 21V 20A Li-Ion Battery Protection Board for Power Tools
5S BMS 21V 20A Li-Ion Battery Protection Board for Power Tools
5S BMS 21V 20A Li-Ion Battery Management Protection Board
Keep your lithium battery packs running safely and efficiently with this high-quality 5S BMS (Battery Management System) Protection Board. Designed specifically for 5-series Li-ion battery packs, this compact PCBA is ideal for electric drills and other cordless power tools. Made in Mainland China.
Key Features
- 5S Li-Ion Compatibility: Purpose-built for 5-cell series lithium-ion battery packs up to 21V charge voltage.
- Smart IC Processor: Uses a dedicated 5S lithium battery IC to monitor real-time cell voltage, charge/discharge current, and ambient temperature for each individual cell.
- Comprehensive Protection: Built-in overcharge protection, over-discharge protection, and short circuit protection for safe, stable operation.
- High Continuous Discharge: Supports 8–20A continuous discharge current — well-suited for demanding power tool applications.
- Ultra-Low Power Consumption: Working current of approximately 25µA and quiescent current of approximately 6µA help extend overall battery longevity.
- Compact Size: Measures just 58 × 63 mm — easy to integrate into existing battery pack housings.
- 2 MOSFETs: Dual MOSFET design (2 MOS) for reliable switching and efficient current handling.
Technical Specifications
| Configuration | 5S (5 cells in series) |
| Charge Voltage | 21V |
| Single Cell Charge Voltage | 4.25V |
| Continuous Discharge Current | 8–20A |
| Overcharge Detection Voltage (per cell) | 4.25V |
| Working Current | ~25µA |
| Quiescent Current | ~6µA |
| PCB Size | 58 × 63 mm |
| Model | 5S21V-2MOS |
| Package Contents | 1 × BMS Protection Board |
What Is a BMS Protection Board?
A Battery Management System (BMS) protection board is the critical safety layer between your lithium cells and your device. It continuously monitors each cell's charge state and intervenes instantly to prevent overcharging, deep discharging, or dangerous short circuits — all of which can permanently damage a lithium battery pack. Choosing the right BMS and installing it correctly is one of the most important steps in building or maintaining a long-lasting Li-ion battery pack.
Important Notes
- Due to manual measurement, please allow a tolerance of ±1–3 mm.
- Colors may appear slightly different on screen versus the actual product due to monitor calibration differences.
- Battery cells, charger, and power tool are NOT included — this listing is for the BMS protection board only.
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Frequently Asked Questions
Q: What does the 5S BMS 21V protection board do for my lithium battery pack?
A: The 5S BMS protection board continuously monitors each of the five series-connected Li-ion cells in real time, tracking voltage, charge/discharge current, and temperature. It automatically activates overcharge protection, over-discharge protection, and short circuit protection to keep your battery pack safe and extend its working life.
Q: Is this BMS board compatible with my cordless electric drill?
A: This board is designed for 5-series (5S) Li-ion battery packs with a 21V charge voltage and a continuous discharge current of 8–20A, making it suitable for most handheld cordless drills and similar power tools that use a 5-cell Li-ion configuration. Always verify your tool's battery specifications before installing.
Q: Does this listing include batteries or a charger?
A: No — this listing includes only the BMS protection board (1 piece). Batteries, charger, and power tool are sold separately. The BMS is the circuit board component that you integrate into your battery pack assembly.