RV Systems
RV Solar - practical energy independence
By By Jerry (RiverGuy) Brown
Oct 25, 2005, 11:47

For the ultimate in RV energy independence, solar energy can't be beat. As long as the sun is shining and your RV isn't shaded, solar panels silently capture the sun's abundant energy. Of course there is much more to the story, we'll introduce the basics in this article. However, anyone who is seriously considering purchase of a solar system for their RV should study the topic in more depth than we can cover here. Noel and Barbara Kirkby’s book "RVers' Guide to Solar Battery Charging" is the definitive reference.

Solar panels, note tilt and "tethered" panel

We'll start with the most visible component of a solar system, the panels. In actuality, these are arrays of individual photo-voltaic cells mounted in a rigid frame. Typical panels today come in 80 and 120 watt capacities, with sizes in the 2' x 3' or 2' x 4' range, so they readily fit on a typical RV roof. They can also be "tethered" via a flexible cable and placed on the ground. One advantage of this approach is that the panel can be oriented to the sun at any time of day. Solar panels have no moving parts and usually carry at least a 10 year warranty. Multiple panels can be wired together to increase the system capacity. For optimal charging during winter months, panels should be tilted toward the south at about a 45º angle.

The second major component of a solar system is a bank of deep cycle batteries. These are different from automobile batteries; they are designed to be repeatedly charged and discharged. Although for optimal performance, they should not be routinely discharged below

Inverter and deep cycle battery bank

about half of their rated capacity. Your battery capacity should be roughly balanced to the amount of solar charging capacity available. Both should be sized to your anticipated needs, figuring the effective battery size at half the rated capacity. In addition, some allowance should be made for cloudy weather, although it’s not practical to store more than a couple of days needs. The Kirkby book includes worksheets for sizing your system. Also, many solar retailers provide online worksheets at their web sites.

The third component of your system is the charge controller; this device ensures that your batteries are not overcharged. Some controllers also include over-temperature protection and special circuitry to optimize charging performance.

Inverter display and charge controller

 

The last component is optional; however, if you plan to operate AC appliances from your solar charged batteries, you will need an inverter. Again it must be sized to your needs. Also many appliances will not function on a low end inverter due to the nature of the AC current they supply. You need to buy at least a mid-range unit that produces "modified sine wave" current. It's also important to get the highest rated efficiency that you can afford.

Wiring it all together is not difficult; many RVers install their own systems, relying on instruction manuals from suppliers. Of course complete dealer installed systems are also available.

Trailer Life's RV Repair & Maintenance Manual RV Repair and Maintenance Manual is the most popular resource for owners who prefer to work on their own RVs.	Woodall's RV Owner's Handbook Learn how to perform preventative maintenance and repairs on your RV from RV technical guru Gary Bunzer.	RVers Guide to Solar Battery Charging RVers who yearn for independence from generators and RV park hookups will find this an essential guide to selecting, buying and using a solar electric system.