21V 7MOS Li-Battery Protection Board for Electric Tools BMS

21V 7MOS Li-Battery Protection Board for Electric Tools

Keep your electric tool battery packs running safely and efficiently with this 21V 7MOS Lithium Battery Protection Board. Designed for DIY enthusiasts, hobbyists, and professionals alike, this compact BMS (Battery Management System) board features a built-in balancing circuit and temperature protection to safeguard your battery cells from overcharge, over-discharge, and overheating.

Key Features

• 21V Rated Voltage – Compatible with standard 5-series lithium-ion battery packs used in cordless electric tools
• 7 MOS Design – Seven MOSFET switches deliver robust current handling for demanding power tool applications
• Cell Balancing Circuit – Automatically equalizes cell voltages to maximize battery life and maintain consistent performance
• Temperature Protection – Integrated thermal cutoff prevents damage from overheating during heavy use or charging
• Overcharge & Over-Discharge Protection – Keeps each cell within safe operating limits for long-term reliability
• Compact Form Factor – Measures approximately 90.5 × 62 mm, fitting neatly inside most standard electric tool battery enclosures
• Durable Construction – Built with a combination of plastic and metal components for lasting durability

Specifications

Who Is This For?

This protection board is ideal for anyone rebuilding or repairing cordless tool battery packs, designing custom battery systems, or working on electronics DIY projects. Whether you're replacing a faulty BMS in a drill, circular saw, or other 21V cordless tool, this board is a reliable, cost-effective solution.

Important Notes

• Slight color variation from product images may occur due to monitor settings and lighting conditions.
• Please allow a minor measurement deviation (±1–2 mm) for stated dimensions.
• Batteries are not included.

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Learn more: EPA guidance on lithium-ion battery handling

Frequently Asked Questions

Q: What type of battery cells is this 21V protection board compatible with?

A: This 21V Li-battery protection board is designed for use with 5-series lithium-ion (Li-ion) battery packs, which are commonly found in 21V cordless electric tools such as drills, screwdrivers, and saws. It is compatible with standard 18650-type or similar cylindrical Li-ion cells arranged in a 5S configuration.

Q: Does this board include short-circuit protection?

A: Yes. The 7MOS design and built-in protection circuitry provide safeguards against overcharge, over-discharge, overcurrent, and short-circuit conditions, helping to protect both the battery cells and the connected device from damage.

Q: How does the balancing circuit work?

A: The integrated cell balancing circuit monitors the voltage of each individual cell in the battery pack and redistributes charge as needed to ensure all cells remain at an equal voltage level. This extends overall battery life and prevents premature cell degradation caused by imbalanced charging.

Q: Are batteries included with this protection board?

A: No, batteries are not included. The package contains only 1 × 21V 7MOS Li-battery Protection Board. You will need to source compatible lithium-ion battery cells separately.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.