Project:DeWalt Battery Replacement

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DeWalt Battery Replacement (NiMH to LiPo)

ProjectDeWalt Battery Replacement 0.jpg
Status: done
Release Date: October 2018
Team: Johannes
Materials Used: DeWalt cordless drill with broken battery, 3S lipo, a balancer board
Tools Used: soldering iron, 3D printer
Software Used: Fusion 360
Approx. Cost: approx. 10 € (without the battery)

A DeWalt_DC740KA Cordless Drill that we used to have had a broken battery which needed to be replaced. In order to replace it, we used LiPo batteries with a custom charging curcuit. In addition to this page, the discussions during the replacement can be read on github. Once done, you can find the repaired drill on the drilling table again!

Battery Circuit

connections between Battery and Protection Circuit:
the inside of the Battery
Originally, the battery circuit was using a 20A protection circuit:
connections between Battery and Protection Circuit
This was modified in order to support 30A:
how I made a 30A protection circuit out of an 20A protection circuit

The battery case had to be recreated. This was done using the 3D Printer. The files can be found here.

Charging Station

Since the battery got replaced, we also needed a new charging station:
ProjectDeWalt Battery Replacement 1.jpg
The charging station is nothing special, just a DC to DC converter with constant current and constant voltage (CC/CV). The current is set to 0.5A and the voltage to 12.5V which provides a safe charging process.
Charging Curve: Dewalt ladevorgang.png
Charging: CC red LED
Battery Full: CV green LED