Voltage Guage on 1991 Spartan Diesel Pusher.

I have a 1991 Spartan Starcraft Diesel Pusher. When driving, the Voltage Meter on the Dashboard is on the line between red and Green. Does that indicate a Problem with the Alternater, or does that mean the Battery is charged? when I hit the Switch for the Batteries on the Monitor above the Kitchen Stove, it says my Batteries are in good shape