Very good to hear I'm not alone in my madness :)
I don't have solar, but do have a RPI2 collecting data from my Magnum and several other custom built WiFi sensors and switches around the trailer... it all ties together in a web based "dashboard" that I can bring up on any tablet or smartphone.
Not familiar with the RPI3, but if it's using one of those tiny microsd cards for the database, you'll want to move the db over to a USB stick or external USB hard drive. The SQL server on my RPI2 burned through two microsd cards already, the constant writes killed the cards dead.
