I checked my single-panel PV test panel setup this morning.
When I opened the garage door, a rodent scurried away - he was small, some sort of vole or mole.
I pulled out the voltmeter to check the batteries.
The four batteries are not perfectly matched, so the voltage was a little higher on two batteries than the other two.
I was also surprised that the number of times the LED was blinking on the solar charge controller indicated that the batteries weren't fully charged. I assume that the settings on the charger were for flooded batteries. I am using gel batteries, which run at a little lower voltage.
I opened up the charge controller to adjust its settings.
Inside, right on the circuit board, was one small mouse poop!
Apparently, the rodent had crawled inside to keep warm! There is only one conduit knock-out hole removed from the controller. All four wires run through it. There is about enough room left for me to stick my little finger through.
Note to self: In finished PV system, use connecting rodent resistant conduit, and mount controls on wall instead of floor.
I have heard that a "computer bug" comes from the early days of electro-mechanical computers. The first time one of those systems didn't work right was from a moth being stuck in a knife switch.
So, maybe computers have bugs, and PV systems have mice!
