RV Solar: Making Power Away From the Grid

Welcome to the first issue of I Can RV! If you're looking for helpful information about boondocking (RVing away from utilities), RV product reviews, information for folks new to RVing, and great places to travel with your RV, you've come to the right place.

To get things rolling for our premier edition, we're combining a couple of categories: Boondocking and New RVer information – in a post relative to solar power. It's a "101" topic, geared for those who don't know much about solar power. Stick around – we'll bring up more advanced topics as the issues go by. And if you have questions, comments, or requests for future information, please drop us a line – use the "Contact Us" button on the right sidebar.

For those who haven't experienced boondocking, a question often pops up: "Where do you get the stuff you need to make your trip fun, and not a bunch of misery sitting around a candle every night when the sun goes down?" For the boondocker, electricity has to come from somewhere. For some, a mechanical fossil fuel-fired generator is the answer. Others find solar or even wind power a happier alternative. Solar and wind power are quiet and the "fuel" costs are free.

In general, solar panels and wind generators produce low voltage direct current (DC) that charges your RV batteries. The batteries store the power up for use when needed--even when the solar panels or wind generators aren't producing power. What about "shore power" devices like microwave ovens, computers, or televisions? Most of these can be operated from stored battery power through the use of an inverter, which changes DC battery power into alternating current (AC) power that's palatable to your shore power equipment.

So, will these "alternative" electrical sources, wind or solar, work for you? In most cases, yes. It really comes down to how much power you use. What's true for one "RV family" probably won't hold true for the next. Space doesn't allow us to go into detail on how to calculate how much power your own lifestyle uses, so we'll need to use a few generalities. In a future post, we'll show you to calculate your own needs.

How Much Power?

All of us need electricity to operate our lighting system, maybe running a couple of lights for four hours a day. It's nice to keep the dishes clean, and take an occasional shower, so electricity will be required for the RV water pump. Let's say that water pump will run a total of 45 minutes a day. Most of us will want to watch a little TV--maybe three hours a day. If you're boondocking in cooler weather, you'll wind up running the furnace fan to take the chill off--let's say just two hours a day. The power these devices consume is measured in "amps," and adding the factor of "how long" they're used equates to a figure called "amp hours."

Using "typical" consumption figures for these devices in our hypothetical example, our generalized RVer will use about 43-amp hours of electricity per day. How many solar panels, or how big a wind generator? Whoa, pardner! First let's talk about where you're going to put that electricity.

A common misconception is that your lights, pumps, TVs, computers, etc., all draw their needs directly from solar panels or wind generators. But the sun doesn't shine at night--when you need those lights, and sometimes the wind doesn't blow. And even with the sun shining brightly, the panels may not be producing enough power to meet a peak of power consumption. Enter your electrical "bank account."

RV Batteries: Your Power "Bank Account"

RV batteries are like a "savings account," for electrical power. With them you can save up the power your solar panels produce, and are critical for wind generator folks who probably produce far more power on a windy day than they can consume. Specially designed "deep cycle" batteries are made for "house" use, that is, they can store and provide power for powering lights, pumps, etc. These batteries customarily produce low amounts of current over a long time. If you're a "motorhomer," you'll also have one or more "starting, lighting, ignition" (SLI) batteries which are designed simply to start up and operate your motorhome engine and associated "running" operations.

When choosing batteries for your RV, never try to make an SLI battery do the job of a house battery--it won't live long enough to tell the tale. Deep cycle batteries for house use are built differently, designed to be deeply discharged and recharged many, many times. SLI batteries produce a lot of current real fast--needed for starting up an engine--and then need to be quickly recharged.

Here's the first place you need to know how much power you actually use. A properly designed electrical system for boondocking has the right amount of battery capacity to provide your electrical needs for at least two days, while only discharging the batteries to half of their capacity. Why so? Well, you may run into a situation where the sun doesn't shine for a day, and you'll need that extra reserve to keep you going. And the other part of the equation? If a house battery is often discharged to less than half its capacity, its longevity will quickly be reduced. Deep cycle batteries can be expensive, so you want to keep them happy and healthy.

So let's take our hypothetical example, where our RVer uses 43 amp-hours of electricity per day. When he "shops" for RV batteries, he'll need to have a battery bank with a minimum capacity of 172 amp hours. How so? Double the use, 43 times 2 equals 86, and then never allow the batteries to be discharged to less than half their capacity, so double that again, 86 times 2 equals 172 amp hours of storage capacity. Since it's a rare day when you'll find a single deep-cycle battery that will have this kind of capacity, you'll need to get more than one battery and wire them properly to get the desired amount of capacity. Let's say our friend finds 12 volt batteries with a capacity of 80 amp-hours. He'd need three of them to meet the needs--and he'd have some extra capacity left over, as his "bank" would provide 240 amp-hours capacity.

Now that we know what our "bank account" looks like in terms of capacity, let's talk about how to put "money in the bank."

Solar: The Primary RV Alternative

Most boondockers start out with solar panels as their primary "alternative energy" source. How much solar power do you need? Figure for every amp-hour of battery capacity, you'll need a ½ a watt of solar panel power. So in our hypothetical example, our RVer could really get away with 120 watts of solar power for his battery bank, provided he boondocks where there's good solar exposure. What is good exposure? Solar panels need to "see" full sun. Add even a bit of a shadow across their surface, or a tiny bit of cloudiness, and energy production drops off significantly. When we consider panel production, we assume six good hours of sunshine a day. If you boondock in cloudy areas, you'll need more solar panel muscle. Figure ¾ of a watt per amp-hour of battery capacity.

Mind you, you'll wind up buying more than just solar panels. Solar panels, left to themselves, can overcharge (read "cook") your batteries. And at night, left to themselves, panels can likewise discharge your batteries. What's needed is a electronic "middle man" who controls the flow of electricity. When the batteries are full, the flow of current is cut off. At night, power is not allowed back up to the panels. That "middle man" is a solar regulator, which acts as a kind of automatic switch.

Where does that leave you in terms of dollars and cents? You can buy all the individual components needed, or some outfits will sell you a complete package. A glance at a popular Internet retailer shows a package, including 200 watts of solar panels, mounting brackets (that allow for easy roof placement of the panel), and a regulator for $324. Add a few bucks for wiring, and you've got your stuff. Of course, if you don't feel comfortable installing a system, you'd have to add installation charges.

But what if your power needs are greater than our hypothetical example? Or what if your needs changed, and you need more power? The beauty of solar power is that it can be expanded with relative ease. Another panel can be mounted on the roof and wired into the existing system without much effort. If our RVer found he needed another 100 watts of power, he could find a suitable panel to add into the system for around $130. Mind you, these are new equipment prices. If you frequent heavily traveled RV hot spots like Quartzsite, Arizona, you'll find solar dealers often have used equipment for less money. Since solar panels don't "wear out," a used panel is not like buying a used car--they're far more dependable.

We hope you've found this information useful. We'll be back with more RV information in our next post. And pardon our housekeeping, we're still adjusting the site -- so that promised "Contact Us" button has eluded us. Meantime, give us a shout at ICanRV at gmail dot com.

photos: R&T De Maris

Updated 7/23/2015 0943 Mountain (AZ) to include new product links.