Wow! Lotta good information in this thread! Let me add a couple details.
First, Wayne wrote
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... the up front cost of a solar system that could fully recharge my batteries when parked in the shade.
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NO solar panel will generate power when it is shaded. As RMR noted, output drops near zero if even a small part of a panel is shaded. There are physics reasons for this, and I will correspond offline with anyone who cares - but the bottom line is that you need full direct sun on the entire panel to get the rated power out of it. This is one reason (in fact, the only reason I can think of) to make your panels portable rather than bolting them to the roof of the trailer. With portable panels on the end of a cord, you can move them into the sun, even if the TM is in the shade. RMR camps mostly in high altitude areas where there is little-to-no shade, so bolt-down panels work well for him. I often camp in wooded areas with some (or a lot of) shade, so portable panels work for me.
And Paul wrote
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So, given 12 hours of daylight, the solar panel should be putting approx ....
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Sad to say, this is way too optimistic. Solar panels don't generate power from simple daylight. They require bright sunlight shining directly on the panel, at not too much of an angle. In most areas of the country, you get about 4 hours of solar-panel-usable sunlight each day, assuming you don't have a complicated steering mechanism to make the panels track the sun's movement. In some really sunny southern areas (like southern California), the average can be as high as 6 hours per day in summer. In northern areas, it drops to as little as 2 hours on a sunny day in winter. Again, RMR noted this when he said he experiences 3-5 hours of good sun in sunny high-altitude Colorado. That's about right.
The Dept of Energy's National Renewable Energy Lab (NREL) has collected an enormous amount of data regarding solar energy. You can find a lot of it at
http://www.nrel.gov/solar/ .
All of this has to be factored in when you size a solar system. Solar is great! But it is not magic.
Bill