Thanks, all - great advice. If I could summarize, it sounds like the best option would be to use a 5W panel, and have it feed into some sort of a box, where I had 3 separate blocking diodes to isolate each charging line, 3 separate fuses, and possible switches for 3 separate leads that would go into each battery. I think it would also be a good idea to have some type of a regulator from the panels to ensure no overvoltage. I assume a 1 Amp blocking diode would be sufficent. Have I summarized that correctly?