While doing some cleaning up and rearranging of the shack during the COVID-19 shut down we are in, I decided I would complete a task I’ve had on the back burner for a while. Building a way to monitor the power supply or, if I am running them, the back-up batteries.

I used an aluminum project box I got off Amazon, a V/A digital read out meter and a shunt. Took an evening of my time between mapping out the cuts, wiring everything in, assembling the box, and what the family needed me for of course!

The finished project doesn’t look bad if I do say so myself, and the wife suggested I build a few more to sell. I may do that as some have already expressed interest to varying degrees. If you would like one then email me at kf4drr@gmail.com and we can discuss. Lead times will vary as this is a hobby and I don’t stock parts and have to divide my time between work, family and then the hobby.

There’s also another version of this display that will handle 20A and tracks the wH used, that might be of interest for monitoring portable operations for some so if you wanted that one I could put power poles in the rear and label accordingly.

With the shunt this meter will do 4.5-100v DC and up to 50A that’s a nice paring as my PS is a 40A model so there’s a bit of headroom left. I mounted the shunt under the desk next to the industrial din rail terminals that I use to wire everything to. Then the DC- has the shunt installed according to the directions between the terminals and the PS. A 3 conductor cable provides V+, V-, and Ain (or A+) up to the display for all the readings made across the shunt via a 16mm 8 pin din aviation connector as is typical on most of our base rigs for the microphone connection.

One thing I noticed was at lower amperage with the shunt installed the amp meter is not as accurate. With the radio in receive and at a low volume it will show 00.0A but the second the radio is keyed it starts reading current draw. I suspect this is a failing of the shunt design and not the meter specifically. Problem is, if I was to power up all 12V equipment at one time the total amp draw would exceed the meter’s ability by itself thus the need for the shunt.

Below is a few photos of the completed project.

Meter front view
All connected up and monitoring the power supply/battery health
Meter rear view
Rear connections are an 16mm 8pin DIN aviation connector