I dabbled with solar in a previous job. Just a one panel, striclty DC operation for remote monitoring stations.
While I had a data logger (Campbell Scientific) for the monitoring needs, I monitored the voltage (if my memory serves me correctly) out of the MPPT Charge controller. I remember being able to graph this and 'see' the charge cycle during the daytime.
It was pretty cool as you could see the charge go to maximum, then tail off, then go into a 'maintenance' mode once the batteries were fully charged. This was important to me at the time as I wasn't sure if I undersized the panel (calculated this by knowing the watts/sq.cm. solar exposure (throughout the year as it changes), then calculate sunlight hours (during winter/worse case), then knowing your system load determine if you have enough charge capability). some times, if we had a series of cloudy days, I could see I would run out of charge and (in the winter) didn't have enough hours of sunlight to get back to a full charage on the batteries (I was in a situation where budget was tight and I couldn't get as many batteries, etc... as I wanted).
I know the old system I upgraded had solar panels that were ten plus years old, and their efficiency was drastically reduced from their initial specified outputs (like 50%). Now, solar panels have a better life span and I believe (again going from memory) that you only net under a 10% reduction in ten years (check this, it would also be dependent on the manufacturer).
Anyway, (sorry, I digressed) it may be interesting to see this charge curve, maybe even compare it over the years to see what is going on with your panels. All it would take is a datalogger (or anything that can capture voltage measurements). You could then see how your panels were 'aging'.
Did your system come with any monitoring capabilites that you could tap into? If not, maybe ask if they could provide some. I don't know the voltage levels that you may encounter in your large installation (as I was just dealing with single panels), but it would be interesting.
It may also be interesting to measure solar output and have that graphed with your data as well.
Anyway, congrats on this system as it is pretty cool to have something like this installed in your home!
Edited by BraveSirRobbin, 14 April 2018 - 05:41 PM.