by Collyn Rivers – Updated 2021
Grid Connect Solar Modules
Using grid connect solar modules for RVs is readily done but needs an MPPT regulator. This article by Collyn Rivers explains how and why it is done.
Grid connect solar modules are often sold very cheaply. Most, however, produce optimum power at voltages that cannot be handled by the 12-24 volt solar regulators used in most RVs. Using grid connect solar modules for RVs is however readily done by using an MPPT (Multiple Power Point Tracking) solar regulator. An MPPT regulator accepts a much wider voltage range. Grid connect solar modules for RVs can also be used in stand-alone solar systems. This article by Collyn Rivers (RV Books) explains how and why.
Grid connect modules are made in a huge range of voltages and sizes. Those of around 300-350 watts tend to be the best value for money. Most output about 50 volts at 60-7 amps.
Juggling volts and amps
An MPPT solar regulator ‘juggles’ incoming volts and amps to produce whatever needed to charge your solar system’s batteries deeply, speedily and safely. For RVs such as camper trailers, caravans and motorhomes this is usually a (nominal) 12 or 24 volts.
Care is needed when buying an MPPT solar regulator when using grid connect solar modules for RVs. Some accept any input voltage from as low as 9.0 volts to often well over 100 volts. But some work only from 9-36 or so volts. Others have an upper limit of about 50 volts. This will be shown in the maker’s literature.
This 400 watts Morningstar MPPT solar regulator is ideal for smaller systems. It will accept input from solar panels up to a nominal 36 volts. (The maker emphasises its suitability for use with grid-connect solar modules for RVs.) Pic: Morningstar.
MPPT regulators do not need prior setting for incoming solar voltage. They do, however, need setting for the type and voltage of the battery/s used (e.g. lead-acid, AGM, gel cell etc), and usually for the capacity (amp hours). This is usually easy to do. If in doubt ask the vendor (or most girls or boys from 9 upward).
The Australian-designed (now US-made) Outback Power MPPT units will accept up to 110 volts or so at up to 80 amps – ideal for larger systems on motorhomes converted coaches – and home stand-alone systems. Pic: Outback Power.
Can I legally install grid connect solar modules for RVs myself?
In Australia, it is legal for non-electricians to install grid connect solar panels for RVs etc, as long as the solar array’s nominal voltage does not exceed about 65 volts. The peak off-load voltage must be under 120 volts dc. This typically limits solar module output to a (nominal) 72 volts.
You are unlikely to experience other than a tingle up to 24 volts. Care is still needed, particularly if working on the RV’s roof. Anything above 50 volts or so can give quite a shock. Unless experienced in electrical work have someone who is to assist you. If the modules produce, or are series-connected, to produce above 120 volts dc, you must use a licensed electrician.
Be aware that many (probably most) ultra-cheap solar regulators are claimed to be MPPT – when they are not. Stay only with known brands.
Full details of all this, plus a great deal more is included in my books: Caravan & Motorhome Electrics, Solar That Really Works! and (for bigger systems) Solar Success. See also related articles (under Power/Solar) on this website. My other books are the Camper Trailer Book and the all-new Caravan & Motorhome Book. For information about the author please Click on Bio.