RV Modifications Part 3- Solar Panel Expansion and Modification

 October 21, 2021

RV Modifications Part 3- Solar Panel Expansion and Modification

Our 2020 Winnebago View 24D came standard with a Zamp 30A Solar Charge controller and two SunPower 100W flexible solar panels installed on the roof with an open plug on the roof and a second open plug in the utilities bay to connect additional solar panels.  The main electrical consumer to worry about on boon docking trips is the refrigerator/freezer which draws 65W in normal operation mode. Having solar will allow the sun to power the refrigerator during daylight hours and hopefully enough solar energy can be stored in the dual 105Ah flooded cell coach batteries (210Ah combined) to run it through the night and during periods of poor lighting.  

Our kids gave us a SunPower 110W flexible solar panel for Christmas, which was a cosmetic match to the existing SunPower 100W panels.  

Winnebago and most manufacturers that use the SunPower flexible solar panels simply glue them down onto the surface of the roof.  This is inexpensive and easy to do, but comes with some inherent problems.  Besides dirt and corrosion, heat is a mortal enemy of solar panels.  Even though the SunPower flexible panels are frequently mounted in this manner, the documentation that came with the new SunPower 110W panel plainly states "Care should be taken to provide ventilation behind or underneath the modules, especially in hot environments."  Searching the internet and reading about other people's experiences with these solar panels, it is clear that some people only get 2-3 years of use out of these panels, while others see many years of reliable service.  I suspect the way they are mounted can significantly effect longevity.  

Not only does mounting the panels directly onto the fiberglass roof of the RV prevent ventilation and cooling for the panel, but it also transfers the heat directly to the RV roof, increasing the heat load that the air conditioner would have to deal with.  It would be ideal to mount solar panels with a distinct air gap between the panels and the actual roof of the RV.  That way, not only will air convection cool the panels, but the panels will also cast shade on the RV roof, further reducing the solar heat load for the air conditioner to deal with in hot environments.  

So I set about manufacturing extruded aluminum frames to provide rigidity to the flexible panels and mounting brackets that would allow the panels to be removed for service or replacement without damaging the fiberglass roof of the RV.  I had to cut the silicone sealant used to glue the panels to the roof using some Spectra fishing line tied between dowels.  This allowed me to remove the panels without flexing them, which might have damaged them worse than the heat might have if I left them as originally installed.  I cleaned the roof and repaired all the holes where screws were used to secure the panels to the fiberglass roof with epoxy and fiberglass.  

Once all the frames were manufactured, I mounted the panels in the frames and then mounted all the frames on the roof.  I also tidied the electrical wires into flexible cable conduits for UV protection and to reduce wind noise and vibration.

The solar panels seem to do a pretty good job of keeping the batteries charged.  The Zamp Solar Charge Controller shows the battery charge status in real time.  So far, during trips, the battery stays more than 3/4 charged unless we use the 2000W Inverter to power the microwave, toaster or induction cooktop to prepare meals.  After using the coffee maker and toaster in the morning, it takes 2-3 hours in the sun to bring the battery back to full if we unplug from shore power before breakfast.  If we start the night with full batteries but no shore power, by morning, the batteries will drop to about half capacity from running the refrigerator, TV, furnace, hot water maker and lighting.  If it's sunny, the battery will be back to full in about 4 hours.  

We also have a Cummins LP generator to supply electrical power when needed, but the solar panels are adequate to maintain the batteries for everything except cooking with the induction cooktop and microwave.  As our flooded cell batteries age, we may eventually replace them with lighter and potentially higher capacity Lithium Iron Phosphate batteries, but these are very expensive (close to $1K each) now.  Hopefully the price will come down in the next year or two as more lithium battery production comes on line.  The Zamp Solar Charge Controller and Zantrex inverter can be easily reprogrammed to work with Lithium batteries, as well as flooded cell and AGM batteries.  While the Amp-hour ratings for Lead-Acid and Lithium batteries are similar, the lithium batteries are about 60% the weight, and supposedly the lithium batteries can be much more deeply discharged without damaging the batteries.  Lithium batteries also can recharge more quickly than lead acid, so they may be inherently better for use with solar chargers.  That will be most likely be an upgrade that will come in 3-4 years, if we end up with typical life expectancy from our current flooded cell group 31 batteries.