DIY Dewalt Battery

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Important Note:
This model is not designed for repair or modification of original Dewalt batteries. Parts are incompatible and will not fit.

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This design supports 21700 and 18650 cells, with options for 5 or 10 cells. There are four types of batteries you can build with this model:

• 5-cell 21700
• 5-cell 18650
• 10-cell 21700
• 10-cell 18650

Regardless of the cell type, the overall size of the battery will remain the same.

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Recommendation:
For the best results, I recommend building a 5-cell 21700 battery. I’ve made two myself and have been impressed with their performance, even after heavy use, drops, and impacts. By sourcing high-quality 21700 cells, you can achieve double the energy storage and power output compared to typical Chinese 18650 batteries found in new Dewalt tools, with minimal size and weight difference.

Why DIY is Better:
Building your own battery offers superior performance to knockoff options sold on Amazon or eBay. By choosing quality cells, you reduce the risk of dangerous malfunctions, and assembling this design with plenty of glue makes it more durable than many commercial alternatives, which often skip adhesives altogether.

A Word of Caution:
While the 10-cell 21700 battery is possible, it has a higher risk of breaking if dropped, and it may not be compatible with Dewalt’s fast chargers. This is because Dewalt uses a different BMS board for their larger batteries. If you choose to build a 10-cell version, please share your experience with fast charging, and I will update this guide.

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Materials Required:

• Four M4 screws (20mm for 5-cell, 40mm for 10-cell)
• One small spring (9mm diameter or smaller, about 15mm long)
• Tube of silicone (caulking or RTV)
• Five or ten 21700 or 18650 cells
• Dewalt BMS board

You can build this for under $30, especially if you find a deal on cells or have some available. For 21700 cells, I recommend:

• Molicel 21700 P45B
• Samsung 30T, 40T, or 50S

Ensure the cells are rated for 20+ amps and avoid old laptop cells.

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Quick Instructions:

1. Check cell voltages – Ensure all cells are within the same voltage range, or the battery won’t charge.
2. Insert the cells – Place cells in the holder, alternating between positive and negative terminals.
3. Spot weld or solder – Use thick nickel strips or copper wire for 1p5s or 2p5s configuration. Ensure strong connections for high current.
4. Attach the BMS and terminals – Follow the wiring diagram, and secure the BMS to the top rack with glue or by melting the plastic. Solder the necessary wires.
5. Assemble for testing – Fit the soldered assembly into the bottom case. Add the LED board, battery level button, release button, and spring. Screw the top shell into place. Check for proper fit.
6. Test functionality – Ensure the battery charges fully and works with your tools. This is your last chance to fix mistakes before gluing.
7. Glue for durability – Disassemble and fill the case with silicone. Focus on the corners and the terminal area where the battery attaches to the tool, as this is the most vulnerable spot during impacts. Avoid gluing the release button and spring.
8. Final assembly – Reassemble the case, double-checking for pinched wires. Allow the glue to cure.

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Helpful Links:
I’m not affiliated with these sellers. Feel free to find cheaper or local alternatives.

• BMS Board
• Samsung 40T 21700 Cells
• Molicel P45B
• Silicone Caulking
• Small Spring

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