Solar panel charging tips for any location, including forests

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By Bob Difley
Boondocking in the national and state forests in summer and using solar power to provide your electricity presents different challenges than found when snowbirding in the Southwestern deserts.

In the desert, because most campsites are open to the sky, you get charging from your panels from the first glint of sun over the morning horizon until it has passed out of view in the western sky. However, since the angle of the sun is lower, you will not receive the charging power your panels are capable of unless you tilt your panels toward the sun’s trajectory across the sky – getting as close as 90 degrees to the sun as possible. Position your RV horizontal to the sun’s movement, and verify that the elevated panels – or other rooftop equipment – do not shade the silicon part of the panel.

Since winter days are shorter, your total charging time will be shorter, and your batteries may not have sufficient time to become fully recharged. Therefore, you may have to schedule more electricity-using hours (meals, showering, computer use) during daylight, so as not to deplete too much from your batteries overnight.

When you move from the desert to a pine-shaded campsite, however, your challenges change. Since the sun during the summer months passes more directly overhead, your panels do not have to be elevated to take full advantage of the sun’s rays throughout the day.

Days are longer so you have many more charging hours every day than in the desert, and since the number of nighttime dark hours roughly equals the eight hours of sleep needed, most electricity-using can be accomplished while the panels are charging if you coordinate your sleeping and rising times with the sun’s rise and set.

But now comes the hard part. Since you are camping in a forest, you will undoubtedly have periods of the day when the sun is blocked from reaching your panels by the magnificent (and tall) trees surrounding your campsite. Short of camping out in the middle of a meadow (which can be nice) you will have to guess where to park to get as many hours of sunlight as possible reaching your panels.

Try to avoid any part of the panel being shaded since that reduces the amount of amps that pass into your batteries. Then watch the sun as it moves across the sky and watch for when your panels are blocked. A small move or repositioning may gain more sunlight. Unless the surrounding trees are very tall or very close to your campsite, you should be able to get enough midday sun hours from overhead to give your system some good strong charging.

The remaining consideration in both desert and forest is the number of overcast or rainy days, which will produce reduced battery charging. It is therefore a good idea to oversize your system slightly to account for all the variables.

(Reprinted from March 2018, for those who missed it.)

You can find Bob Difley’s RVing e-books on Amazon Kindle.

##RVT899


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Tommy Molnar
Tommy Molnar

I just took the lazy man’s way out and upgraded from our ‘puny’ 375 watt roof-mounted solar array to a 700 watt array, and upgraded our controller to an MPPT unit. We mostly boondock out here in the west but when we camp somewhere in the trees, we make sure we are judicious in our power use. So far, so good. We always get a full charge on our two 6 volt batteries. And, at 73, I no longer have the zeal to climb up the ladder twice a day to prop up or take down the panels.

Wolfe
Wolfe

Im not planning on manually propping up panels either… i’m planning motorized auto- tracking that *I* don’t direct. Based on directional light sensors or “max wattage wiggle”, the panels aim themselves. It looks easy, but I may be delusional. 🙂

Tommy Molnar
Tommy Molnar

You figure that stuff out, Wolfe, and report back. It sounds like it’s way over my pay grade – 😉

Ronnie Bolling
Ronnie Bolling

I haven’t bought it yet since my Promaster van is still in the local conversion shop and I want to test my capabilities first, but the Yeti solar generator (vs a propane or gasoline powered generator) and the Boulder briefcase portable solar array is what I’m leaning towards to supplement the rooftop panels the shop is installing on my van. This system can be easily moved to a sunny spot and another plus is you can recharge the generator using shore power or the 12 volts from your RV while driving.

Graybyrd
Graybyrd

I’m a disciple of the KISS system: first, we bought two 100-watt rigid panels; second, we bought a 35-foot extension cable with panel connectors; and third, we installed an MPPT solar charger. Our truck camper has room for only one Group27 deep cycle battery. We hook the panels in series; with higher series-connection voltage the MPPT charger converts enough power to charge even on overcast, dim days. I deploy the panels propped up in the clear beside the truck camper, angled to the brightest portion of the clouds. It works.

Wolfe
Wolfe

At my largest, I ran four class-29 120AH batteries, no solar. I’d usually just run between plugging into shore power or drive-charging, but was able to shove 50A of charging into the 480AH bank from a generator in a pinch. The whole bank died a couple of winters ago, so now I’m back to 2, and thinking to add solar instead of more batteries, so probably going to follow your path… Maybe two 100W solar panels ($70×2) and MPPT controller ($15), for $155 before installation to “play with” and get a feel for what I’d need IF more. I’ll probably… Read more »

Wolfe
Wolfe

I’ve now seen several people with fairly simple (sometimes genius-level, analog simple) sun trackers on outrigger panels, and wonder why more people aren’t doing this, since folks have claimed they get 30-40% extra power with their existing panels. The panels don’t have to move fast, so truly tiny motors geared way down can swing pretty large arrays. Panels mounted on a tripod to avoid shade or re-aim seems far more versatile than roof-mounting, although not quite as convenient. Are motorized panels that unknown? With panels at 70 cents a watt, solar is getting very tempting, but I’m shaking out the… Read more »

Robbie
Robbie

I think the reason they don’t purchase sun trackers is the added expense. Instead, I just bought extra panels. The only time I have to tip my panels is in December and January….by February, all my panels lay flat. We hit 100% SOC almost every day.

Wolfe
Wolfe

Probably true for smaller installations — the tracker has to cost less than 3rd panel to be worthwhile for 2. Anything larger, I still think tracking wins $$$(?). Part of that guess is that I lean towards outrigger panels in the first place, to avoid shade or to aim manually. I assume a tripod is slightly more expensive than stationary mounting is(?). Then there’s the debate over single or double axis tracking, since east-west is seemingly more critical than up-down. Both DIY projects, I’ve seen “4-sensors and microcontroller”-type and a brilliant counter-polarity-solar analog-drive system (No brain, the unshaded solar panel… Read more »