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I installed 520 watts of solar panels on my Georgetown roof. You can add up how many watts of power your lights and appliances use, and for how long each day, to try and get an estimate of how much solar you will want. When I did the math, it looked like two 140 watt panels would suffice. The problem is that the panels are mounted flat on the roof, and most formulas assume the panels are aimed at the sun. Fortunately, I had planed for the possibility of needing more panels and had space on the roof. I used a larger charge controller that could accommodate the additional panels. The next year I added two more 120 watt panels (the 140 watt ones were unavailable), and this has worked very well for my needs when boondocking.
There are three types of solar cells commonly available. Monocrystaline cells are the most expensive, and most efficient (18-22%). They are made from a single silicon crystal that is sliced into thin wafers. Polycrystaline cells are made from poured silicon, and are lower priced and slightly less efficient (16-18%). These are the most commonly used cells on solar panels, and they are what I have. Both of these types of cells are then mounted into a rigid frame panel. The third type is thin film. They are often flexible, and appear as a single surface rather than individual cells on a panel. Because they are much lower efficiency (7-12%), you would need a larger surface area.
My solar panels are attached to the roof using 8 "Z" brackets per panel, with #10 stainless steel screws to secure into the plywood underneath the fiberglass roof. Before installing the screws and brackets, put a gob of Dicor over each drilled screw hole. After all the brackets are secured to the roof, cover them with additional Dicor.
Use #10 UL listed 4703 sunlight resistant photovoltaic wire from the panels to a roof junction box. From the roof junction box down to the controller and then to the batteries use #4 or #6 cable to minimize voltage drop. Because the heavier gauge cable is typically not available as sunlight resistant, I installed it in conduit on the roof. Install the solar charge controller as close as possible, but never in the same compartment as the batteries.
Select a roof location where the panels will not be shaded by any vents, air conditioners, TV antenna, etc. Because most solar panels are made of individual cells wired in series, if just one cell gets shaded it can shut down the entire panel. It's just like those old Christmas lights, where if one bulb burned out, the whole string stopped working.
The first photo shows the four panels installed on the roof. The second photo is of the basement compartment that is closest to the batteries with the charge controller, disconnect box, and an inverter.
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2010 Georgetown 373
2013 Jeep Wrangler
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