Caution: Solar panels in daylight are ‘live’ so care should be exercised in handling or testing.

When looking into solar panels you will come across the term ‘photovoltaic’ (PV) which Wikipedia defines as ‘the field of technology and research related to the application of solar cells for energy by converting solar energy (sunlight, including ultra violet radiation) directly into electricity(solar electricity)’. 

Solar panels are made up of cells and there are three types of cells – monocrystalline solar cells, polycrystalline (or multi-crystalline) solar cells and amphorous solar cells.  These solar cells are then physically and electrically joined and placed in a frame forming a solar panel or PV module.  A number of solar panels joined together is called a solar array.

BP Solar and Kyocera use polycrystalline or multi-crystalline cells in series for their solar panels.  BP Solar states these type of solar panels charge batteries virtually in any climate. 

Solar panels or solar modules come in various sizes and capacity ranging from 5W up.  To some extent the number of solar panels and the size of the solar panels you can have or fit to your RV will be dictated by the dimensions of the roof and the available space after the placement and number of roof hatches such as the four-season hatch or skylight as well as any roof top air conditioner.

Solar panels are heat sensitive so that is why you see them mounted on a bracket spaced above the roof of your caravan or RV leaving some air space underneath the for cooling.   Also, as the solar panels are heat sensitive they produce less power when they get hotter particularly in the north of Australia and even around Brisbane in summer as the writer has experienced.  Some solar panels are less affected by some shade, some will completely shut down if shaded by as little as 5%, but as yet no solar panel will work in complete shade.

Collyn Rivers * has stated - ‘Outputs vary from type to type, but in typical RV installations most solar modules produce a bit over 70% of their apparently claimed output. Many modules have a small panel on their rear face that shows what they actually produce. For an '80-watt' module this is usually about 58 watts’. Collyn suggests dividing the watts by 16 or 17 (not 12V ie: 80W ÷ 17 = 4.7A) for a truer output.

* Reproduced by express permission, Collyn Rivers, Caravan & Motorhome Books, Broome, WA 6725.  This article is protected by Copyright.  www.caravanandmotorhomebooks.com

Using the example above, 22 watts is ‘lost’.  Essentially the solar panel may be rated 80 watt at full sunlight at a particular temperature but if the temperature is too hot then the voltage produced is less than the rating.  There is a feature called Maximum Power Point Tracking (MPPT) used in some of the more expensive solar electric charge controllers which you could investigate further – it may be too technical for most applications.