It looks like Windy Nation is using the same Solar 30 Charge controller that BFL and I are running. The Bulk Voltage charge rate is adjustable on that model, up to 15.0V, on the lcd display, but it's best to verify what you are getting at the battery, once the battery is close to fully charged. Good unit, I like mine a lot. A setting of 15.0V on my unit would put 15.3V to the battery. For my Trojan T-1275 sweeper battery. It's a lot like a Screwy 31 in it's voltage and charging needs.
The end voltage you get at the battery terminals from the controller will depend a lot on the gauge of the wire you run, and the length of the final run from controller to battery. Keep it short and run fat wire.
