I have created an adapter to use a Dewalt 20v Lithium Ion Battery with my 18v Dewalt tools.
DISCLAIMER/WARNING - Use at your own Risk. it can be Dangerous to over discharge Lithium batteries. -Risk of Fire or Explosion-
The 20V Dewalt Tools that use this type of Lithium battery have the battery protection circuitry inside the tools, not the battery, and as such the user of this adapter must be careful not to over discharge the battery.
This design includes an inexpensive Lithium battery monitor with Low Voltage Alarm (between $2-$5), that is typically used in the RC hobby.
I did not need supports for the top (18v) part, or the side clips, however it is necessary to use support on the bottom (20v) part. It prints upside down.
I printed the top battery clip (18V), and the top part of the adapter with ABS.
The side clips, bottom battery connector (20V), and bottom part of the adapter with PLA
It will likely work with All ABS or All PLA, just be careful not to break of the tabs on the top (18V) battery prongs when assembling if using all PLA
The 20V contacts locations are set up to push 24 to 28 gauge (~0.5mm) metal strips through to connect to the terminals of the battery and the tool. - I cut them from a sheet of 24 gauge 260 brass that i purchased from Amazon (search "260 Brass Sheet, 24 Gauge)
You could use other types of metal such as galvanized strapping for hanging pluming pipes, or similar, as long as it can be soldered to.
For the wires, I used 10 Gauge automotive wire for the battery connections and some strands of cat3 wire to make the connections to the battery monitor.
See the pictures below for details on the connections.
You will need to be able to solder a good solid connection between the top connector and the bottom one.
When assembling, I made the terminals for the top, then pushed them through the small top clip and then soldered the 10 gauge wire to them.
next i pushed to top connector and wires into the top part of the adapter, and sized up the length of the wires so that they would reach the B+ and B- terminals of the 20V connector block without having too much wire length. - It is a tight fit by the time everything was assembled.
The connections to the battery monitor were fairly simple, you must remove the terminal strip from it before soldering the small wires to the terminals for each cell. The battery monitor connections are (from left to right, looking at the front of it) B-, C1, C2, C3, C4, and B+ (which is C5) as labeled on the 20v battery. - See the pictures below. - don't forget to add a small wire from the B+ and B- connector for the battery monitor.
Be sure that the connectors are not shorted to each other when assembling, as the battery could burn/explode if shorted out.
you will need 4x #6-32 x 1/2" machine screws to assemble the top and bottom half. i had to cut the front two off at about 3/8" to allow the 20v battery to fit. Leave the back screws long so that they hold the 20v battery connector in place.
I used a spring out of a click pen, cut in half) for the side clips. - stretching them slightly. The clips are held in place by the top and bottom half.
20v battery connections (looking at the back of the connector)
Top 18V terminal cut and bent
18V terminal pushed over top connector. - Solder your 10 Guage wires to the bottom of the connector before installing it in the top of the adapter.
18V tool connections polarity.