DEWALT battery

DIY battery for DEWALT tools. Uses either 18650 or 21700 cells, with options for 5 and 10 cells.
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updated January 20, 2024

Description

This design is intended for use with 21700 cells, but 18650 cells will work. I highly recommend using 21700 cells. This comes with 5 and 10 cell options as well, so there are 4 types of battery you can build (5 cell 21700 or 18650, 10 cell 21700 or 18650).

I recommend building a 5-cell 21700 battery. I made 2 of these and have been very happy with their performance for over a year. I have dropped, hit, and generally abused them over that time. By sourcing your own high quality 21700s you can get double the energy storage and power output compared to the Chinese 18650 batteries that typically come with new dewalt tools.

Please be aware of the drawbacks of building a 10 cell 21700 battery. The print will be more likely to break when dropped, and you most likely cannot take advantage of dewalt's fast chargers, which results in very long charge times. Dewalt uses a [different BMS board](https://www.aliexpress.us/item/3256805075613649.html) for their large batteries.

Materials:
(x4) - M4 screws (20mm length for 5 cell, 40mm length for 10 cell)
(x1)  - small spring 
        - silicone (caulking or RTV)
(x5 or x10) - 21700 or 18650 cells
(x1)  - Dewalt BMS board

I recommend printing in ABS, nylon, or polycarbonate because they have much better impact resistance.

The total cost can be less than $30 if you get a good deal on cells or already have some. Some good 21700 cell options are Molicel 21700 P45B, Samsung 30T, Samsung 40T, or Samsung 50S. Any cell with a rating over 20 amps works.

Guide:

1. Check cell voltages are within the same range. If their voltages are too different the battery will not charge.

2. Insert the cells into the holders alternating positive and negative

3. Spot weld or solder very thick nickel strips or copper wire to the cells to form 1p5s config. This needs to carry a lot of amps so make sure the connection is good.

4. Attach BMS/terminals to the top rack with glue or using soldering iron to melt the plastic together. Solder the BMS wires. You can see if the BMS is working by pushing the button on the led board.

5. Assemble the battery by putting the cells+bms into the bottom print. Place the led board and the battery level button print into their slots. Get the release button in place with a spring on the circle area of the top rack. Screw the top case shell into place. Check the fit and make sure no wires are pinched.

6. Test the battery to make sure it charges and works with your tools.

7. Disassemble and use silicone glue to fill in all the empty space in the battery. The more glue you use the stronger the battery will be. The important areas to glue are the corners and the area around the battery terminals where the tool holds onto the battery. Do not glue the release button.

8. Reassemble and double check no wires are pinched.

Example links to items you need. I have no affiliation with these and you should be able to find cheaper listings.
BMS board:
https://www.aliexpress.us/item/3256805535552741.html? 
https://www.aliexpress.us/item/3256803602190043.html

21700 cells:
https://www.18650batterystore.com/products/samsung-40t
https://www.18650batterystore.com/products/molicel-p45b

Silicone (kitchen and bath caulking or RTV is fine):
https://www.homedepot.com/p/GE-Silicone-1-10-1-oz-Clear-All-Purpose-Caulk-2708911/100091111
https://www.amazon.com/Permatex-80050-Silicone-Adhesive-Sealant/dp/B0002UEPVI/

Springs (10mm diameter or smaller, around 14mm height):
https://www.aliexpress.us/item/3256801222091501.html?
 

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The author marked this model as their own original creation.

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