21V 18650 Battery Protection Board for Makita – 6MOS 30A / 5MOS 25A

21V 18650 Battery Protection Circuit Board – Compatible with Makita Power Tools

Keep your Makita 18V/21V lithium-ion battery packs running safely and reliably with this high-quality Battery Management System (BMS) Protection Board. Available in two configurations — 6MOS 30A and 5MOS 25A — this 5-string (5S) protection board is engineered to guard your 18650 cells against overcharge, over-discharge, short circuit, and overcurrent, dramatically extending the life of your battery pack.

Whether you're rebuilding a worn-out Makita battery or upgrading an existing pack, this CE-certified replacement circuit board is a cost-effective and dependable solution for DIY enthusiasts, technicians, and tradespeople alike.

Key Features

• Compatible with Makita 18V/21V 18650 battery packs — drop-in replacement for standard 5-string configurations
• Two variants available: 6MOS 30A (higher current capacity) and 5MOS 25A (standard performance)
• 3 alloy MOSFETs for efficient switching and low heat generation
• Built-in temperature control — thermal protection prevents overheating during charge and discharge cycles
• Copper hardware contacts for superior conductivity and durability
• Large board design (5-string/5S) — accommodates standard 18650 cell layouts
• CE Certified — meets European safety and electromagnetic compatibility standards
• Full protection suite: overcharge, over-discharge, overcurrent, and short-circuit protection
• Low voltage rating: below 75V DC / 50V AC — safe for residential and workshop use
• Made in Mainland China

Specifications

Why Replace Your Battery Protection Board?

A faulty BMS is one of the most common reasons a lithium-ion battery pack stops charging or loses capacity. Instead of buying an entirely new battery, replacing just the protection circuit board is a smart, affordable fix. For more information on lithium-ion battery safety, refer to the U.S. Consumer Product Safety Commission's Lithium-Ion Battery Safety Guide.

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Frequently Asked Questions

Q: Which Makita battery packs is this protection board compatible with?

A: This 21V 5-string (5S) 18650 BMS protection board is designed for Makita 18V/21V lithium-ion battery packs that use standard 18650 cells in a 5S configuration. Always verify your existing board's dimensions and cell layout before purchasing to ensure a proper fit.

Q: What is the difference between the 6MOS 30A and 5MOS 25A variants?

A: The 6MOS 30A version uses six MOSFET transistors and supports a continuous discharge current of up to 30A, making it suitable for higher-demand power tools. The 5MOS 25A version uses five MOSFETs and handles up to 25A — ideal for standard Makita tool usage. Choose based on your tool's current draw requirements.

Q: Does this board protect against overcharging and short circuits?

A: Yes. This BMS protection board includes full overcharge protection, over-discharge protection, overcurrent protection, and short-circuit protection, as well as a built-in temperature control function to prevent thermal runaway — a key safety feature for 18650 lithium-ion cells.

Q: Is installation difficult? Do I need special tools?

A: Installation requires basic soldering skills and appropriate tools (soldering iron, multimeter). It is recommended for experienced DIYers or electronics technicians. If you are not comfortable working with lithium-ion cells, please seek professional assistance, as improper handling can be hazardous.

Q: Does the package include batteries or a charger?

A: No. The package includes 1 × Protection Board only. Batteries and chargers are sold separately.