The batteries in a non charging state will be about 12.4 to 12.6 volts. Later in the day after the sun has been up but before say 3PM check the batteries again to see if they are higher than when you checked in the dark. You could also throw a blanket over the panel and see if the voltage changes.
2007 Country Coach Tribute 260 Sequoia
40' DP w/Cat400, F494513
Live next to Yosemite
Tror Fourwinds Class C, 1961 American Eagle 01 Bus