Portable – adjustable power supply with Bosch 18V battery (based on ZK-4KX)

This mini power supply module is based on the ZK-4KX converter and delivers an adjustable output from 0.5V to 30V, up to 3A.
I have a bunch of 18V Bosch Professional batteries around, so I wanted them to power the module in order to keep everything tiny and portable, yet packing a big deal of autonomy.

Disclaimer

Electricity should always be handled with care. I am not responsible for your build or modifications, the step-by-step instructions show how I built my own version, not a guarantee of safety for your setup. Please do your own research before attempting this build, use properly rated components, double-check all wiring and solder joints, and test everything thoroughly before use.

Parts

I designed this model around the components I already have on hand, so I can't provide a reliable link for every part. Depending on the dimensions of the components you use, minor adjustments to the models may be required.

Electronics

• 1× ZK-4KX module

• 1× Banana female connectors (Aliexpress)

• 1× DC 5.5×2.1 female connector (Aliexpress)

• 1× SPST switch (Amazon)

• 1× 3A ATO fuse

• 2× male spade connectors

• 2× female spade connectors

Assembly

• 5× M3 Ruthex inserts

• 5× M3×12mm screws

• 4× M3×8mm screws

• 4× M3 nuts

• 2× M2 Ruthex inserts

• 2× M2×8mm screws

Step by step

1 – Insert the two male spade terminals into the battery adapter (make sure the polarity is correct) and secure them with hot glue while fitted on the battery. Before gluing them in place, double-check that their angle aligns properly with the holes in the base plate.

2 – Fit all the components into the front and rear panels. It is a tight fit, so patience may be required.
The power-supply-banana-tongue part must be printed 4 times, its role is to prevent the banana connectors from twisting once screwed on the panel. Depending on your printer's tolerances, the openings may require a bit of sanding or trimming before installation. Pliers can help insert the parts.

3 – Add all the threaded inserts (3× M3 under the back panel, 2× M3 under the front panel, 2× M2 for the fuse holder)

4 – Install the switch and fuse holder. Position the fuse holder and its terminals where the wires are under the least amount of mechanical stress, then glue the holder to the base plate using cyanoacrylate. A bit of hot glue on the two terminals help keeping them secure. Screw the lid on afterwards. 

5 – Wire and insulate all connections according to the wiring diagram.

6 – Join the two halves and add install the remaining screws.

7 – Once powered on, make sure to configure the undervoltage function of the ZK-4KX to prevent deep discharging of the battery.

Credits

• The ZK-4KX counterform has been taken from this model by @Vikvoch

• The fuse holder has been adapted from this model by @Cederb