Milwaukee M18 12.0Ah Battery Rebuild Kit - 15x21700 Case + BMS (No Cells)

Milwaukee M18 12.0Ah Battery Rebuild Kit – 15×21700 Case & BMS

This DIY rebuild kit is designed for rebuilding or repairing Milwaukee M18 12.0Ah lithium-ion power tool batteries. It includes a complete replacement housing, internal metal contacts, hardware, and a compatible BMS board. Perfect for experienced battery builders looking to restore performance using 15×21700 lithium-ion cells.

This is a compatible replacement kit. It is independently manufactured and is not an original Milwaukee-branded product.

Kit Includes:

• Milwaukee M18 12.0Ah compatible battery case (top & bottom shell)
• BMS / protection board
• Nickel-plated internal contact plates
• Spring contacts
• Thermal pad and insulation pieces
• Screws and assembly hardware

Cell Configuration:

• Designed for 15 × 21700 lithium-ion cells (5S3P layout)
• Fits Milwaukee M18 tools and compatible chargers
• Cells are NOT included

Battery Capacity:

This kit uses a 5S3P configuration, so the finished pack capacity is approximately three times the rated capacity of each individual 21700 cell. Fifteen matched 4,000mAh cells produce a pack of roughly 12Ah. Actual capacity, output current, and runtime depend on the cells selected and the quality of the assembly.

What Is Not Included:

• 21700 lithium-ion cells — you supply your own
• Spot welder
• Battery charger
• Power tool
• Battery assembly service

Important Information:

• This is a DIY battery rebuild kit
• Battery assembly experience is required
• Spot welding is strongly recommended
• Use only properly tested and closely matched cells. Do not mix cells of different brands, models, capacities, ages, or condition.
• Always verify cell orientation, polarity, insulation, and pack voltage before connecting to a tool or charger
• Please review all product photos carefully before ordering

Additional Parts and Resources

For additional battery-building parts — cells, nickel strips, insulation rings, BMS boards, connectors, and other DIY battery supplies — visit RenewSpark.

For helpful tools, calculators, rebuild planning utilities, and technical information, download the RenewSpark Tools app.

Milwaukee and M18 are trademarks of their respective owner. This compatible product is independently manufactured and is not produced, sponsored, or endorsed by Milwaukee.