I'm creating a solar panel to charge a pair of old 6V Trojan batteries in series that I use for a remote phone antennae. The antennae uses about 2 watt of power full time and up to 9 watts when on hook. They're remote so can't check but seem to remember on full charge they get up to about 14.5V. I have a bunch of cells I picked up that generate about .52V and supposedly about 2000ma.
I don't want to put in an expensive charge controller just for this application so wanted to know four things.
First what size panel to I need to create to charge the batteries but not overcharge them?
Second what size blocking diode do I need so as not to discharge the batteries in the night back into the panel.
Thirdly what "formula" do I need to consider to extend the application. In other words if I decide to put in a bank of 10 12V batteries linked as pairs to create a 24V system (the antennae supports 12-48v) using the same power consumption above what would I need for the blocking diode. I know it's a ridiculous example but it'll help me understand.
Lastly - what am I forgetting?
Thanks very much.