In 2018, I made a little readout box so I could see what the voltages were from the battery, panels, battery at the charge controller (so I could tell if there was a problem with the battery wires), and at "Load" on the controller.
These little digital volt meter (DVM) mulit-colored readouts are cheap on Amazon or eBay:
Mounting the readouts and switches behind the clear cover of the box:
Back then the kitchen table was my electronics bench.
The LED readouts and toggle switches for them get mounted in the box and wired up:
Here was the charge controller at the time:
All together, on the bench:
Fire it up! Connected to solar system:
Hey, this reminded my nephew of the electronics in the Back To The Future vehicle, haha. I'm just missing a Flux Capacitor: