Trailer owners need to calculate the Amp Hours (AH) usage per day to select the proper solar panel size required to charge their battery bank. One Amp hour equals the battery bank providing 1 Amp of energy each hour. A battery bank that holds 100 Amp Hours of energy provides 25 Amp for four hours or 50 Amp for two hours.
If you use 50 Amp Hours each day, and have the proper size battery bank, you should have the ability to draw the necessary power (50 Amp ) without draining the batter bank below 50 percent. This means the solar panels must provide 50 Amp hours of the energy a day to replenish the battery bank. Find out the number of Amp required to run each appliance. Multiply the Amp by the hours of usage. Add the AH for each appliance to get the total AH.
Find out the number of Amp Hours the solar panel produces per hour by determining the amperage rating. For example, if the brand states the panel generates 8 Amp in sunny, clear conditions, this means the panel produces 8 AH per hour. Keep in mind, this represents the maximum energy production under ideal conditions: full sunlight and cloud-free. An RV owner in the sunny southwest experiences sunny conditions most of the time compared to an RV owner in the Midwest.
Determine how many hours of sunlight the panel will receive on an average day. Use this figure to calculate number of AH a panel can generate each day. If area receives an average of 5.58 hours of sunlight each day, multiply 5.58 by the panel AH to get the Total AH for each panel. Using the above example, 5.58 multiplied by 8 Amp equals 44.64 Total Amp Hours. Therefore, the solar system requires two panels to replenish the 50 Amp used from the battery bank on a daily basis.
Most panels have brackets that mount to the trailer's roof. Rubber roofs usually have a plywood base, which allows the installer to screw the panels into place just about anywhere on the roof. When using this method, do not insert screws into joints between the plywood. For a fiberglass roof, drill pilot holes in the fiberglass material large enough for the screw's diameter. This prevents cracking the panels. On metal roofs, locate the rafters underneath the roof and screw the solar panel mounts into the center of rafters. Avoid mounting panels directly to the roof. Use a sealant around any roof penetrations to protect against water infiltration.
Follow the manufacturer's wiring instructions for the solar panels. Most trailers require 12 volts, which requires the "parallel" wiring technique. This means connecting the positive-to-positive wire and negative-to-negative wire. The other wiring option, "series," connects positive wire to negative wire. However, the series wiring method increases the system's voltage, which could damage the solar charger. These wires run to a concentrator. Make the final connection to the solar charger and link to the battery bank.
