Know Your Solar: Solar 101 (kind of)

This is a short article I did for the upcoming issue of OutdoorX4 Magazine 


Occasionally I get asked to do a “Solar 101” talk, starting from how a solar cell actually works through the end result of a charged battery. My experience, however, is watching eyes glaze over when I start talking photons of light and electrons. While thinking about these details makes me feel all warm and fuzzy, let’s talk about how adding solar to your rig can keep you out on the adventure far away from a plug or a generator. I have blogs on my site at if you are moved to read more on how a solar cell works.

First, I am not a solar purist as much as I enjoy the ability to stay off-grid as long as I want. If you need to run a large roof air conditioner in a camper I would be the first to recommend a good generator and a way to bring plenty of gas with you. Sure, solar can do it but it’s not cost-effective and would take up precious real estate. Outside of a large roof AC you can absolutely reasonably power your rig with solar. Before you spend any hard earned money, it makes sense to do a power need inventory. Figure out how many amps per hour each item you typically use draws. Google is your friend, as there are plenty of calculators for this along with lists of common items and the amps they draw.

I am on the road at least four months a year for Overland Solar in my small Class B RV with two small group 24 coach batteries without plugging in. Like most readers of this magazine, I don’t consider staying in some RV park off a highway with hookups my idea of fun. I have all of the typical inefficient RV appliances and watch plenty of TV at night. The biggest draw in any system is the old incandescent lights. These need to be thrown in the trash and replaced with LED bulbs! I am not writing this to sell more bulbs but if you just check how many amps one single 12-volt bulb in a fixture is drawing, you will see that you can have 6 LED bulbs on for the same power and they last 50,000 hours, giving off better light. That old standard bulb draws more power than my camper refrigerator. My consumption averages 46 amp hours over 24 hours and I use my Overland Solar 90 Watt to charge my batteries back up daily.

The key to making small, truly portable solar work is the type and quality of the cells and the ability to move the panel at least twice a day so you can double the hours of sun exposure. Solar panels mounted flat on a roof are only going to produce about half the power of the same panel that is moved a couple of times to follow the sun, angled towards the sun generally around 45 degrees. In addition you need to camp in the sun with a vehicle or RV getting hot inside so the roof panels work. With a portable, you can camp in the shade and put the panel in the sun, then just point it where the sun will rise when you go to bed, reposition around noon, and one more time towards sunset. If you are going to stay with a roof-mounted system it should at least be on some type of a bracket so it can be angled or you lose around 30% of the available power.

Solar cell type and quality matter!

There are three types of cells found in solar applications but the big two are Polycrystalline and Monocrystalline. The cheap solar panels found too often are Polycrystalline even in some well-marketed name brand applications. Polycrystalline cells are made of molten silicon cast into ingots or drawn into sheets, then sliced into squares. While production costs are lower, the efficiency of the cells is lower too — around 15 percent. Monocrystalline (also called single-crystal) cells are made in long cylinders and sliced into round or hexagonal wafers. While this process is energy-intensive and wasteful of materials, it produces the highest-efficiency cells — as high as 25 percent in some laboratory tests. The third type is amorphous silicon and is so inefficient it is rarely used.

Who makes the cells and the quality control in production is a major concern. A good monocrystalline cell made with junk bonding is a waste of good money. I have seen some pretty inventive marketing on how a cell is sold as made in the USA or Germany when it was produced in China but holds an office in the USA or Germany where it was “designed” or “crafted.” Stick with a solid brand. I use Bosch cells due to quality and high efficiency but there are others that are good. When I was still doing panels by hand, I tried and tested quite a few cells but Bosch was always the best made and, just as important, was consistent in quality.

The solar panel runs the power through a charge controller which limits the charge to your batteries and should be a smart charger that can be set for different batteries. An AGM battery needs a higher charge than a standard flooded battery. The controller will go into a trickle charge when the correct voltage is reached to maintain the battery without overcharging and ruining your investment. You can use an MPPT or PWM controller. The difference would take a separate article but I use PWM controllers in my units and my off-grid home where I live full-time. I have tested both and am just not sold on the much more expensive MPPT controllers. If costs come down in the future they may be worth the money for the small additional power.

Solar power is direct current (DC) so they are ready to charge your battery system. If you need AC power you just add an inverter to your battery. Here is another area where I am not sold on very expensive inverters. I have had two well-known, very expensive, pure sine wave inverters in both my RV and off-grid home fail within a year. The $50 truck stop inverter in the RV I replaced one with has gone strong for three years. Some high definition TVs will not work well on the cheaper modified sine wave inverters but for everything in the RV and all of the electronics in the home I have never had a problem.

Battery selection is also worth its own article and there are too many variables to go into detail so, again, I have a blog on my site if you are looking for more information. One major issue is to make sure you are buying a true deep cycle battery. Many batteries are sold to customers as deep cycle batteries when they are really dual use batteries. A good deep cycle battery does not need to cost any more money. Leave those dual use batteries on the shelf or there will be frustration and headaches if you try to run a camper or expedition rig on one, even with daily solar charging.


What about clouds?

Solar panels do best on clear sunny days but still produce power with cloud cover or fog. It depends on how thick the cover is but you will generally see 10-25% of the rated capacity. I live off-grid in Washington State, not really known for an abundance of sun. Solar panels are actually more efficient at cooler temperatures than hot ones. Germany gets only about as much sunshine as the State of Alaska, but Germans have successfully installed about 25 gigawatts of solar power– half the entire world’s supply. There is also the edge of the cloud effect that actually magnifies a solar cell’s output higher than clear sun so passing clouds are not always a bad thing.


If you have any questions or would like some additional information, please feel free to shoot me an email. I am still a small enough company that I can usually respond pretty quickly. I built a small place in the middle of 40 acres and have been off-grid for two years living on two of my first 150-watt prototypes and another 100-watt panel so, yes, it absolutely can be done in comfort. I rented out my house in the Seattle area and really don’t miss the grid. I have all the things I had in the old house (expect a monthly power bill) including a big TV with streaming internet and am able to type articles like this many miles from the closest power pole or neighbor but the view is spectacular.


Brian Wurts