Panels are rated for a standard sun (1000 W/m^2 insolation) at I think 25C. This is for the maximum power point, which is almost never the voltage to charge the battery at. The ones I've played with (powerfilm 5W, HQRP 20W) do more or less make their rated power in full sun (really blue sky), and 5-20% of that in clouds.
I have a 20W panel with not particularly good siting that gets sun from about 1030 to about 1600. I have seen 1.3A from it, charging a 12V AGM battery with a simple on/off controller (brunton). Over the last 2 months I have gotten an average of just over 3 Ah per day. On really sunny days I get 7Ah. So a solar setup really needs enough batteries to run for most of a week (at least in New England), and enough panel to recharge if you have 1.5 sunny days in that week. So for a fixed installation take daily use in Ah multiply by about 15 (1 week, don't discharge more than half) to get battery capacity take daily use in Ah, multiply by 2h of average good sun per day, and find a panel that can produce that current in full sun. All that said, I have taken a single 7Ah battery and the 20W panel with charge controller, and found that in mostly sunny conditions that powers a kx3 indefinitely just fine. Do not even think of using a panel without a charge controller. You will end up with excessive voltage and fry the battery. 73 de n1dam ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
