Multipurpose Portable Power – David VK3RU November 2023
I had been contemplating for some time a little multi purpose battery pack which might be handy around the shack and be used when out and about, the result is the following small project.
The main objectives were to construct a battery pack suitable for both portable radio (QCX) and testing/repairs at the local Opp Shop. I volunteer at the Opp Shop testing donated items including clocks, radios and toys and it would be handy to complete testing without the need for new and often expensive batteries which if included, make an item far too expensive.
Comprising Anderson Power pole output to power portable radio gear and a variable regulated output to binding posts all protected with fuses in both legs to the battery. My project was built using a 3D printed box, Battery from Paul (3AHM), Voltage and Current regulator from EBay, a few bits and pieces from the junk box and an afternoon in the shack.
To kick off I ordered a battery and charger from Paul and my mate in Adelaide was good enough to convert a rough sketch into a suitable program to print up a very nice 3D printed box. That box arrived yesterday and during the course of the day, one of my projects was finally complete.
Along the way there were a couple of learnings.
- The controller OFF button only isolates the output but the regulator remains powered up, so a switch was required to isolate the battery when not in use.
- Adding a rocker switch necessitated cutting an extra hole in the box which is not as easy as you might imagine. I discovered there is not a lot of material between the top and bottom surfaces of 3D printed box and it is not easy to file, a coarse file or Stanley knife works best.
- The regulator input/output negative is not common necessitating some sort of additional point of multiple connection. My solution was a fuse in the negative rail to the battery providing extra solder points.
- At this stage I am not sure if we will ever cause the regulator fan to run, but if we start pushing the power envelope, some ventilation might need to be considered.
Testing complete and it works as intended although I did wonder what value fuses to install. The QCX draws only 300mA and most of my Opp Shop items are low current items but we also need to consider the charging circuit. Charging is via the Anderson Power pole connections and being common, it is also in the fused circuit. The charger supplied by Paul shows 12VDC at 1A so I figured a 2A fuse was safe for charging, the QCX has a 500mA in line fuse and I can set the regulator current to whatever suits the purpose up to the fuse rating.
Recently I had occasion to deploy my new battery pack at the Opp Shop as there was no suitable 9V battery available and it worked a treat, so we can tick that box. All that now remains is to get out of the shack and give it a test using the QCX in a park or mountain top.