Lately I’ve been playing with the BM2 battery monitors, available on ebay and automotive shops for 20-30 dollars. They attach to the batteries, connect to your phone or PC over bluetooth and hold the voltage history for 30 days. In addition the software provides low voltage alarm notifications. There are other automotive testing functions as well. The software allows you to set names for each sender, and show multiple devices on one screen.
The downsides are limited bluetooth range. However, they’ve been useful. When I first got them, I noticed that one of the tower trailers was suddenly not producing voltage in the early afternoon. It turned out, with the sun getting lower in the sky, one trailer was in the other’s shadow. Moving them further apart fixed the issue.
Below is a voltage measurement from before and after clearing 3 inches of snow off of the solar panels. It clearly does make a difference.
Being able to keep an eye on the voltages from a nice, warm, location, can be a boon here in the frozen Minnesota tundra.
Above chart from the end of a cloudy day… I imagine with the snow removal it will do much better when we actually get some direct sunlight too.