Without doubt, our solar setup has given us more independence, more freedom and more fun as full-time RVers than anything else

in this lifestyle. It has allowed us to go anywhere anytime. If there is one area that RVers should spend money, besides purchasing

the rig itself, it is in getting set up to use the sun for electricity. In this section I describe the two systems we have had, offer a little

theory, discuss the installation and some of the discoveries we have made along the way.

The biggest advantage of a solar charging system in an RV is that the system is working from dawn to dusk, silently and with no

smell or fuel cost, no matter where you are or what you are doing. Towing, parked at the grocery store, or camped, the batteries are

being charged. They start getting charged before you finish breakfast, keep charging while you hike or go sightseeing, and continue

all day, rain or shine. They don't quit charging til nightfall. You never have to think about the batteries getting charged. It just

happens. In our current rig I feel like we have electrical hookups all the time -- and we never get hookups!

We have had two very different solar setups, a modest one on our Lynx travel trailer and a more robust one on our Hitchhiker fifth

wheel. In both cases we camped without hookups 85% of the time or more, relying on our solar panels to provide all our electrical

needs. We did purchase a Yamaha 2400i generator in January, 2008, but have used it only rarely since then: a few times after many

dark winter days to give the batteries a boost, and a few times to run the air conditioning in the summertime. Other than that, we just

lug it around and turn it on every 4-6 weeks to flush the gas through the lines.

Our "modest" solar setup allowed us to use almost every appliance we own, however, we had be conservative with our electrical use

over the winter. Our "robust" system is like having full electrical hookups wherever we go. No conservation necessary! On our

biggest electrical use day to date, we watched our 26" LCD TV with its huge surround-sound system and sub-woofer for 15 hours (it

was the Olympics!) and ran the computer for 7 hours, made popcorn in the microwave and ran several lights for 4 hours in the

evening. The next day the batteries were fully charged by mid-afternoon.

BASIC ELEMENTS OF THE SYSTEM: BATTERY CHARGING and CURRENT CONVERSION

The basic components of each solar setup was the same, and is comprised of two major subsystems. One subsystem charges the

batteries and includes:

• batteries

• solar panel(s)

• charge controller to protect the batteries from overcharging

The other subsystem converts the battery DC power to AC power so we can run our AC appliances like the TV and electric razor.

This includes:

• inverter(s)

The difference between the systems is the overall capacity, that is, being able to run

more appliances at once, being able to run more appliances for a longer time at

night, and being able to run larger appliances.

So, in a nutshell, the batteries, panels, charge controller and inverter(s) do the same

job as plugging a generator into the shore power connector on the side of the rig.

The panels and charge controllers charge the batteries. The inverter makes it

possible to use AC appliances, though not necessarily via the AC plugs inside the

trailer. The cost of each setup was comparable to the cost of a similar capacity

generator, $970 for the modest setup (compare to a Honda 2000i) and $3,900 for the

robust setup (compare to an Onan 3.6 kW). However, unlike a generator, there is no

noise, no fuel cost, and no smell.

The solar panels are mounted on the roof. In the Lynx we had just one panel, and

at first we didn't want to make holes in our perfectly watertight roof just to mount the

panel. However, after loading it in and out of the trailer a bunch of times and

worrying about it getting damaged while traveling, Mark finally decided it was safer

on the roof.

Our panels are mounted flat. Some people mount them with tilting brackets so they

can be tilted towards the sun. We were shown a persuasive graph indicating that the

difference in solar collection is just 11% between flat and perfect orientation towards

the sun, and if we absent-mindedly drove off with them tilted up they could be

destroyed in the wind. The real deciding factor for us was that it would be a 6-week

wait for the store to order tilting brackets, and this way we don't ever have to climb up

on the roof to tilt our panels or even think about our solar charging system at all once it was installed.

(See "A Winter's Tale" near the end of this page for what we learned about flat versus

tilted panel performance in wintertime).

Cables run from the panels through the roof down to the charge controller which is

mounted somewhere in a storage compartment where you can see it. Another wire

run connects the charge controller to the batteries in the battery compartment. The

solar panels send as much power to the charge controller as they can get from the

sun. The charge contoller monitors the power coming from the panels and gives the

batteries only what they can handle so they don't get fried.

The inverter(s) are installed separately. These can either be portable units that plug

into cigarette lighters in the rig or larger units that are permanently wired to the

batteries. When using a small inverter connected to a cigarette lighter, AC appliances

are then plugged into the 3-prong AC outlet on the inverter. Turn the inverter on and

then the 3-prong outlets are "live" and you can run your appliance. Alternatively, a large inverter (to support a vacuum cleaner,

microwave, hair dryer, toaster, coffee maker, etc.) gets installed very close to the batteries and is wired direclty to them permanently.

An extension cord can be run from the AC receptacle on the inverter into the interior of the trailer. Or the inverter can be wired into

the AC wiring of the trailer. In either case, the inverter needs to be turned on in order to provide AC power. When we had the small

charging system on the Lynx, we also kept a cheap inverter in the truck that we could plug into the cigarette lighter to charge the

laptop, camera batteries or toothbrush as we drove around town.

When purchasing a solar setup, it helps to work with a knowledgeable solar power store and salesman. We have seen huge

variations in what stores charge for solar equipment.

A MODEST SOLAR SETUP

A fully functional, inexpensive solar setup, comparable in price and power output to to a portable Honda 2000i inverter generator

($970 or so) is simply:

• Two 6-volt batteries giving 220 amp-hours of capacity

• 130 watts of solar power

• A charge controller that can support 10 amps

• A portable inverter that can supply 150 watts of AC power

This is essentially the setup we had on the Lynx travel trailer. It could power a 19" LCD TV and DVD player, radio or laptop as well

as charge camera batteries, razor, toothbrush, cordless drill, cell phone, etc. It could not run the microwave, hair dryer, toaster,

coffee maker or vacuum. For those, we simply installed a larger inverter connected directly to the batteries (not a portable inverter).

This system is the smallest size system I would consider for an RV if you want to drycamp or boondock for more than a night or two

and be comfortable.

This setup worked great in the spring, summer and fall when the sun was high in the sky and the days were long. We never thought

too much about our power use until the middle of December when the days got short and the nights got long and cold. Then we

began to long for a bigger system. On long cold winter nights we had to conserve our use of lights and the TV to make sure our

furnace (which used a lot of battery power) could still run. We used oil lamps a lot on those winter evenings. If we had stayed in that

trailer longer we would have installed a vent-free propane heater that did not use any battery power (we eventually did that the

following winter: see the heater page).

I think every RV sold should have this kind of a charging system installed as standard equipment, as it is perfect for all part-time

campers who spend weekends and week-long vacations in their RVs during the summer months.

In 2007 we installed in the Lynx:

• Two Energizer (Sam's Club) 6-volt batteries giving us 220 amp-hours of capacity ($130)

• One Kyocera 130 watt solar panel ($609)

• A Morningstar Sunsaver charge controller that could support 10 amps ($55)

• A portable Radio Shack 150 watt inverter connected to a DC cigarette lighter in the trailer

[to run everything except the vacuum ($59)]

• A Pro One 800 watt inverter connected to the batteries with an extension cord run into the interior of the trailer

[to run the vacuum ($75)]

The total cost for this setup was $972, including $44 for wire, connectors and mounting brackets. We were quoted $135-$350 for

installation. Mark is very handy, though not a Master Electrician, and the installation was easy for him.

SOME THEORY -

CHARGING & CONSUMPTION

Here is some theory to explain why the above system is "sufficient" but is not "robust." When it comes to a solar battery charging

system, the concept of power charging and consumption is very simple. The amount you can use, or take out of the batteries, is

essentially only as much as the amount you can charge or put into the batteries. If you use (or take out) more than you charge (or

put in), sooner or later your batteries will be discharged and dead. The batteries are just a temporary storage place for electricity.

They act as a flow-through area for the power you are going to use.

The most important part of any solar setup is the amount of charging going on

(i.e., the total size, or capacity, of the solar panels), and you want that to be

greater than the amount of electricity you use. More must go into the batteries

than comes out. You can have an infinite number of batteries and eventually

discharge them all completely if you repeatedly use more electricity than your

solar panels put in. Too often we find people who want to add batteries to

address their power shortages when what they really need to do is add more

solar panels. Also, as a rule of thumb, you don't want to take out more than 1/3

to 1/2 of the total capacity of the batteries in one night of watching TV and using

the lights.

AMPS and AMP-HOURS

Appliances use amps to run. Another unit, the amp-hour, refers to the number of amps an appliance uses when it is run for an hour.

For instance, an appliance that uses three amps to run will use up three amp-hours when it runs for an hour. These amp-hours will

be drawn from the batteries, and the batteries, in turn, will look to the solar panels to recharge the amp-hours they have forked over

to the appliance. It is for this reason that you need to know how many amp-hours you will use in a typical day: ultimately those amp-

hours must be replaced by the solar panels, so the number of panels you purchase will be determined by how many amp-hours you

use in a day.

To estimate how many amp-hours you might use in a day, estimate how many hours each appliance will run and multiply that by the

number of amps the appliance uses.

We have measured some of the appliances in our trailer, and this is how many amps they use:

Single bulb DC light

1.5 amps

Dual bulb DC light

3.0 amps

Dual bulb fluorescent light

1.5 amps

19" LCD TV

5.5 amps

DVD / CD Player

0.5 amps

15" MacBook laptop, on & running

5.5 amps

15" MacBook, off and charging

1.6 amps

Sonicare toothbrush charging

0.1 amps

FM Radio w/ surround-sound

3.0 amps

12' string of rope lights

3.3 amps

Most DC appliances list their amp usage in the user manual or spec sheet. Most AC appliances list their wattage instead of

amperage. So for AC appliances you have to convert the wattage rating to get the amperage rating. You can get a rough estimate

of the number of amps that an AC device will use simply by dividing the wattage by 10.

Technically: Watts = Volts x Amps. AC circuits run at 120 volts and DC circuits run at 12 volts, so on a DC circuit an appliance will

use 10 times as many amps as it will on an AC circuit.

To determine most precisely how many DC amps an AC appliance will use when running on an inverter, start by dividing the watts by

12. However, inverters are not 100% efficient. Typically they are only about 85% efficient, losing a bunch of watts to heat as the

inverter runs. So it takes more watts to get the required amps out of an inverter, the exact figure being 1 / 85%. This means you

have to divide your DC amps (that watts / 12 figure you just obtained) by 0.85 to get

the most accurate result. This is messy. Rather than dividing watts first by 12 and

then by 0.85, you can simply divide the watts by 10 and get a pretty close estimate.

Our 19" LCD TV is rated at 65 watts. How many amps DC? 65/10 = 6.5. We

measured the TV at 5.5 amps at the volume we like to hear it. If we cranked the

volume the meter went up to 6.5 amps. Likewise, the laptop is rated for 65 watts. As

we opened and closed files and started and stopped various programs, the meter

zoomed all over the place between 3 amps and 6.5 amps. Most of the numbers were

near 5.5 amps. When we shut down the laptop and left it plugged in for charging, the

meter dropped to 1.6 amps.

WHERE DO THE BATTERIES FIT IN?

Battery storage capacity is measured in amp-hours (Ah), and more is better. As a starting point, most new RVs come equipped with

one 12-volt Group 24 battery which will give you about 70-85 Ah of capacity. Upgrading to two 12-volt Group 24 batteries (wired in

parallel) will give you 140-170 Ah of capacity. If, instead, you replace the single dealer-installed 12-volt battery with two 6-volt golf-

cart batteries (wired in series) you will get 220-225 Ah of capacity.

Assuming the sun has charged the batteries completely by nightfall, and sticking to the rule of using only 1/3 of your total battery

capacity each night, you will have as little as 25 Ah of nighttime capacity if you keep the single 12-volt battery that came from the

dealership, or you can have as much as 75 Ah of nighttime capacity if you install two new 6-volt batteries. You can always add more

batteries too, the only limit being where to put them.

AND HOW ABOUT THE SOLAR PANELS?

Battery capacity is only part of the story. The ultimate limiting factor is how many amp-hours the solar panels can put into the

batteries during the day. If the solar panels are sized too small to charge the batteries sufficiently each day, you will eventually

discharge the batteries over a series of days and they will be dead.

Solar panels are rated in terms of Watts. The relationship between the Ah that the panel can store in a battery and its Watts rating is

not straight forward. Suffice it to say that a 130 Watt panel produces 7.5 amps in maximum sunlight, and both of those numbers are

available in the specs for the panel. What isn't stated is how many Ah a panel will produce in a given day. We have found that our

120 watt and 130 watt panels produce between about 8 Ah and 40 Ah per day depending on the season and the weather, ranging

from a dark winter day to a sunny summer day. Latitude also plays a role (more sun to the south) and there are more fully sunny

days in the west than in the east. However, in general our panels produce around 25-30 Ah per day each.

If you have the time and inclination, you must figure out how many Ah you use each night, make sure that that number is less than

1/3 of your total battery capacity AND make sure your panels can provide that many amp-hours of charging each day. But all that

sounds very difficult. Luckily there are some rules-of-thumb.

NEVERMIND THE THEORY - HOW MUCH DO WE REALLY CONSUME?

We met a couple living on their 27' sailboat on its trailer in the desert (they were on their way to launch it in the Sea of Cortez), and

they were using just 6 amp-hours per day because they had a tiny solar panel. In the Lynx we used about 25-35 amp-hours per day.

In the Hitchhiker we use an average of 90-120 amp-hours per day.

In the Lynx, with its modest solar setup, we used just one light at a time and often used oil lamps, watched TV or DVDs for a few

hours a night some nights, listened to the radio or CD's for a few hours some days, charged the laptop and other appliances for a

few hours at a time. On most winter mornings we woke up to find the batteries fairly well discharged (our simple 4-LED display would

have two or three LEDs lit, indicating partial discharge). We did not use our microwave. We could have if we'd installed a slightly

bigger inverter, but we rarely used one in our stick-built house, so we didn't bother in the trailer. The Sunsaver charge controller did

not indicate how much charge was going to the batteries, but I would estimate it was typically anywhere from 1-6 amps per hour, or

about 25 Ah per day in winter.

In the Hitchhiker, with its robust solar setup (described below), we often have two, three or more lights on at night, use the laptop and

26" TV with a large surround-sound system for as many hours as we like, run the microwave once in a while, and even use the hair

dryer. We never think about consumption but instead get a kick out of watching the charge controller as it pumps amps into the

battery -- or doesn't -- depending on how thirsty the batteries are.

So as a rule of thumb, here is the number of amp-hours consumed per day:

• 6 Ah = living ultra-conservatively

• 25 Ah = live modestly in spring, summer, fall, but get very conservative in winter

• 120 Ah = live just about the way you do in your house

SOLAR SHOULD BE INSTALLED ON ALL RVs

It is strange to me that RV dealerships don't sell solar setups as a dealer add-on. Many sell generators, but I haven't found any that

sell solar in an easy-to-purchase package. With a little effort they could design three standard systems, modest, better and deluxe,

and give their customers something really valuable -- a trailer that is self-sufficient right there in the dealer lot, without hookups.

Watching the Tour de France on TV, we noticed that most of the RVs lining the roads had solar panels. Sadly, that is not true on this

side of the Atlantic. Also, most trailers in the US are sold with one 12-volt Group 24 battery. That is inadequate for anything more

than stopping at a rest area for lunch! 12-volt "marine" batteries are hybrid batteries. They are designed to be both "starter"

batteries to start a marine engine, and to be "house" batteries to provide power to lights and appliances. 6-volt golf-cart style

batteries are strictly "house" batteries designed only for deep cycle use, not for engine starting. Trailer batteries aren't used to start

any engines, so those 6-volt golf-cart batteries are really superior for powering the lights and appliances in an RV. It doesn't make

sense for dealers to sell trailers for tens of thousands of dollars with one measely, insufficient 12-volt Group 24 battery instead of two

6-volt golf-cart batteries, when the cost difference is just $65.

GET YOUR HANDS DIRTY!

It is hard to play with solar until you actually take the

leap and buy a panel, charge controller and cables and

hook it all up. However, you can definitely get the

hang of how inverters work without a huge financial

outlay.

Here is a sampling of inverters along with current

prices, specs and reviews. They are 175 watt, 400w,

700w, 1200w, a true-sine 1500w (explained below)

and a generator. The inverters we bought aren't the

more well-known brands, whereas the ones shown

here are. If you are curious about all this and haven't

used an inverter before, pick up the cheapest one and

try it in your car to see how it works. You can charge

your cell phone or laptop or run a small TV just as you

would in your RV.

This will help give you a hands-on feeling for the "how

to run AC appliances from a DC battery" half of the

equation. The other half is the solar panel and charge

controller, of course, and since it involves purchasing

cable and connectors, is not easy to experiment with

until you take the plunge.

The Yamaha generator rounds out the list to a nicely

formatted 6 items but is also here because it is the one

we have. As mentioned above, we do not use it to

charge the batteries, but we do use it to run the 15,000

BTU air conditioning unit about 5-10 nights a year.

BATTERY TYPES

The factory standard 12-volt Group 24 battery found in most RVs will give you 70-85 amp-hours of capacity -- not enough. It would

make so much more sense for the dealers to sell standard (or sell an upgrade kit for) two 6-volt batteries, giving you 220 amp-hours

of capacity (upgrading to two 12-volt Group 24 batteries gives you only 140-170 amp-hours of capacity). The 6-volt batteries will also

give you true deep cycle batteries rather than hybrids. Cheap dealer-quality 6-volt batteries cost about the same as cheap dealer-

quality 12-volt batteries. So why bother installing an upgrade to two 12-volt batteries? We bought our Lynx with two 12-volt

batteries, not knowing the difference. By winter we had upgraded to two 6-volt batteries, giving us much more capacity to run our

lights and appliances for more hours at night and on consecutive cloudy days when the batteries didn't get fully recharged.

I have heard the very bizarre argument that it is better to have two 12-volt batteries in parallel instead of two 6-volt batteries in series,

because if one battery fails in the 12-volt pair you will still have a working battery, whereas if one fails in the 6-volt pair you will have

nothing. If you have a solar charging system and you pay attention to your power consumption you will never have a total battery

failure. Check your batteries every so often to make sure the water level is topped off -- and add enough distilled water to bring any

low cells up to the bottom of the neck of the cell. A single battery of a pair will never just up and fail if it is charged daily and you take

care of it. However, if the battery gods are just dead set against you and one does fail, you will be without power only for the length

of time it takes to go to a hardware store and get another. Worst case, you can place the new battery on the ground outside the

trailer and hook it up temporarily to get the water pump (or lights or TV or whatever appliance you absolutely have to have) working

again until you sort out your longer term battery solution.

6-volt batteries have the same footprint as 12-volt Group 24 batteries, however the 6's are about 3 inches taller. So, before

upgrading, you have to check the height in your battery compartment. Our Lynx travel trailer had enough room in the battery

compartment on the hitch to fit the larger 6-volt batteries. The Hitchhiker fifth wheel required quite a bit of retrofitting, both at the

factory and at the dealer. The NuWa factory custom installed four vented battery boxes for us, but they were for 12-volt Group 24

batteries. The dealer cut the bottoms off the battery boxes and ran some angle iron along the bottoms so the batteries could be

recessed, sitting on the angle iron, and still fit their vented tops in the basement compartment of the trailer. NuWa now offers four

factory installed 6-volt battery boxes that are properly sized with their 2009 models.

Batteries are racist and ageist. They like to be surrounded by other batteries of the same age, make and model. Don't mix and

match 6- and 12-volt batteries or old batteries with new ones. Batteries are very altruistic, and the strong ones will spend all their

energy charging the weak ones and trying to help them keep up. So if you are upgrading, consider just replacing the batteries that

you have with a new matched set.

A ROBUST SOLAR SETUP

In a nutshell, in order to run your RV with the same level of comfort as a house, using all of your appliances whenever you feel like it

without thinking about conserving at all, you will need at least the following:

• Four or more 6-volt batteries giving you at least 440 amp-hours of capacity

• 360 or more watts of solar power

• A charge controller that can support 30 amps or more

• An inverter that can supply at least 1000 watts of AC power

That is a very big system and is comparable in cost and power output to a 3,500 watt or larger onboard Onan diesel or propane

generator -- $3,500 or so. It will power everything except the air conditioner, regardless of weather or season.

In 2008 we installed on our Hitchhiker fifth wheel:

• 4 Trojan 105 6-volt batteries (2 in parallel to make two 12-volt batteries, and those 2 pairs in series with each other) ($315)

• 3 120-watt Mitsubishi solar panels and 1 130-watt Kyocera panel, for a total of 490 watts of solar power ($2,364)

• 1 Outback MX-60 60 amp charge controller ($495)

• 1 Exceltech XP 1100 watt true-sine wave inverter ($545)

The cost for all of this was $3,869, including $150 for wire, connectors and mounting brackets. Mark did the installation. My rough

guess is that the installation might have cost $500 if done by someone else. We would have bought 3 Kyocera 130 watt panels to

complement our existing one, but they did not manufacture one that was easy to connect. Mitsubishi's 120 watt panels could

connect to our Kyocera more easily and were about $25 less per panel, so we chose those instead. Our batteries are fully charged

by the end of each day, rain or shine, and we typically use anywhere from 75 to 120 amp-hours of battery power per day. The

charge rate varies greatly, but it is typically anywhere between 4 and 25 amps per hour, depending predominantly on the state of

charge of the batteries (moreso than on the weather). The charge controller deliberately reduces the charge rate as the batteries

approach full charge. We have seen charge rates of 10 amps per hour in driving rain storms and in full shade. That is more than

our Yamaha 2400i generator could produce; it charges at just 8 amps per hour!

The solar panels are mounted on the roof in series with 10 gauge wire running

between them. (See section at end of this page about Series versus Parallel wiring).

The wire comes up to the panels from a ground location on the trailer frame in the

basement compartment and it returns to charge controller in the basement. The two

wires running to and from the basement are housed in a 6' piece of 1" PVC pipe that

we placed behind the refrigerator, and the wires run from the top of the fridge vent

out onto the roof. Because the panels are in series, only 7.5 amps of current runs

through these wires.

Down in the basement, more 10 gauge wire runs from the charge controller to the

batteries. This section of the wire sometimes carries 25 amps or so, as the charge

controller delivers as many amps to the batteries as they can take, and at times they

want a lot. In hindsight I'm not sure it was any easier running the wiring through the fridge vent down the back of the fridge than it

would have been to drill a hole in the roof above a closet and run the wire down the inside of the closet through a hole drilled in the

floor to the basement compartment. Mark did the closet method in the Lynx, but we learned later most installers use the fridge vent,

so he tried it on the Hitchhiker.

Our inverter is wired in a manner that is ideal for us but would be greeted with jeers

and dire warnings by Master Electricians. It works well for us because we never get

electrical hookups. If you switch a lot between hookups and boondocking, then this

method would not be a good idea.

First we unplugged two appliances that use a lot of AC power when they sense AC

power on the line. We did not want the inverter to be taxing the batteries in order to

run AC appliances we did not need or that could run from some other energy source.

The first appliance we took out of the AC circuitry was the fridge. We simply unplugged

its AC plug in the back, effectively forcing it to use propane gas to run all the time.

Ours is a model where you can push a "Gas" button on the front to force it to gas, but

by unplugging it from the AC outlet it can never switch by mistake.

The second appliance we removed was the DC converter box. This box is provided so the trailer can run its DC appliances when it is

plugged into shore (AC) power without having to use the batteries. It takes a lot of AC power to run, and it turns on as soon as it

senses AC power on the line. When we boondock we want to run our DC appliances from our batteries, so the DC converter needs

to be shut down. We simply unplugged its AC connector from its outlet. When first learning about this stuff, I found the terms

"inverter" and "converter" very confusing and did not understand the difference between them. If you are a little puzzled too, check

my notes about these two components at the bottom of this page.

Next, we wired -- no, Mark wired -- the inverter directly to the batteries. Then he took a 3-prong extension cord and cut off the

female end. He purchased a male connector and wired it to where the female end had been, effectively making a male-male

extension cord. He plugged one end into the inverter and the other end into the AC outlet where the DC converter had been plugged

in (this just happened to be a handy AC outlet near where he had installed the inverter). Bingo! When the inverter was turned on we

had AC power to all the outlets in the trailer.

The huge caveat about cheating like this -- and it is cheating -- is that the shore power outlet on the

outside of the trailer is LIVE. Don't stick your finger in there. Actually, don't stick your finger in any

outlet... More importantly, don't try to plug something into the shore power outlet on the trailer

(either electrical hookups OR a generator) when the inverter is turned on -- things will blow up. This

is the reason that you don't want to have this kind of quasi-wiring if you frequently switch between

shore power and boondocking.

If you are going to be switching between shore power and inverter power frequently, you need to

wire the inverter into the AC wiring via a subpanel connected to your AC distribution panel, and

other websites describe this process in beautiful detail.

AN IMPRESSIVE MOMENT

We have seen some remarkable numbers on the Outback charge controller, showing how many

amps are currently going into the batteries or how many amp-hours have been collected for a given

day. I wanted to get a photo of the display for this web page. We were outside Bryce Canyon,

Utah, in early August and it was around noon -- a very favorable location, season and time of day

for solar collection. However, this particular day was extremely gloomy. There were no visible

shadows on the ground, and storms were advancing towards us in the distance.

I took a photo of the black sky over the field next to our trailer. Then I turned around and looked at the Outback. it was putting 25

amps into the batteries! As I stood there the sky around us lightened a little -- still no visible shadows, but everything lightened just a

bit. I looked at the Outback and it was now putting over 28 amps into the batteries. I took a photo. Soon the sky darkened again

and the Outback fell first to 19 amps, then 15, and eventually to 10 as it started to pour.

INVERTER and CONVERTER CONFUSION

If you are like me, the terms "inverter" and "converter" sound so similar it seems they might be one and the same thing. They are

actually two very different components with very different missions in an RV.

Inverters

The AC inverter takes the DC battery power and uses it to make AC power so you can run things like TVs and DVDs and charge

things like your camera batteries. You turn on the inverter, plug an AC appliance like an electric razor or TV into it, and poof, the

razor or TV works.

Inverters can be "true sine wave," meaning the AC power signal coming out of the inverter is identical to the power signal of a wall

outlet in a house, or they can be "modified sine wave." meaning the waveform is clipped at the top and bottom and is stair-stepped in

between rather than being a smooth sine wave. True sine wave inverters start at about $400 for the smallest ones whereas modified

sine wave inverters top out at about $400 for the largest ones. We purchased a true sine wave inverter for our "robust" solar setup,

because it matched the quality of the system and our particular unit was noted for its ruggedness (we run it 15 hours a day,

sometimes 24). Our Exeltech true sine-wave inverter is designed to operate medical equipment, so it provides exceptionally clean

and stable AC power. Ironically, some RV parks have unstable AC power that can damage AC appliances in an RV; our inverter

power is cleaner and more reliable! Desktop computers, laser printers, TV and stereo equipment are the most likely appliances to

have trouble with modified sine wave inverters. However, we never had a problem with any of our appliances using those inverters

with our modest solar setup on the Lynx. Modified sine wave inverters often have loud fans, and Mark did have to put WD40 on our

Radio Shack inverter twice when the fan quit working unexpectedly.

Inverters come in two flavors: plain inverters and inverter/chargers. An inverter/charger can be a very efficient battery charger when

you are plugged into shore power. However if your solar charging system is effective and you aren't going to plug into shore power

very often, there is no need to pay the extra money for an inverter/charger rather than a plain inverter.

Converters

The DC converter takes the AC power coming in from the shore power cord (via electrical hookups or a generator) and gives power

to all the DC appliances in the rig so the batteries can take a break. It essentially does what the batteries do, but does it only when

there is shore power.

The DC converter in an RV also charges the batteries while connected to shore power. Some converters have sophisticated multi-

stage charging mechanisms, and others simply provide a trickle charge.

The DC converter is not involved in the solar setup. In our "robust" solar setup the DC converter is actually unplugged because our

inverter powers all the AC outlets in the rig. By design, if it were plugged in, the DC converter would automatically impose a huge

demand on our batteries whenever we turned on the inverter.

A WINTER'S TALE - To Tilt or Not To Tilt

(Added January, 2009)

When I first wrote this page, we hadn't yet experienced a winter with our new solar setup. Now, in January, we are some three

weeks past the winter solstice, and we have all kinds of data to report.

We didn't pay any attention to our charging capabilities until about November 15th. At that point we were in Yuma, Arizona, about as

far south in the western US that you can go, and I noticed that the charge controller wasn't reaching "float" mode by the end of the

day. So we started turning off the inverter when we went to bed at night. Then all was well again (the inverter uses about 2 amps

per hour, even when nothing is running, so that conserved an easy 40 amps per day).

Around December 1st we moved to Quartzsite, Arizona, and set up camp next to our friends Bob and Donna Lea Jensen, veteran RV

boondockers who have been wintering in the Arizona desert for over 20 years. We compared notes on our solar setups and

discovered some interesting results. The Jensen's setup includes 3 Kyocera 120 watt solar panels in parallel and a Heliotrope

charge controller.

Their panels are mounted on tilting brackets, and they oriented their rig to maximize their southern exposure. Each of their panels

was a perfect 45 degrees toward the sky facing due south. We were nearby, oriented to maximize the sun coming in our windows in

the morning. By this season, the sun was rising in the southeast, skimming along above the horizons, and setting in the southwest.

Our panels follow the roof line of our trailer, so in our current orientation two of our panels were tilted about 5 degrees to the

northeast, one faced directlly upwards, and one faced about 10 degrees to the southwest.

In general, as we compared our charging pattern with the Jensens, we found that our charge controller would work all day to achieve

a full charge, which it generally did by about 4:45 in the afternoon (at which point it could no longer get anything from the sun). The

Jensens were fully charged by 1:00 p.m., and their charge controller quit trying to put anything into the batteries after that (our

charge controller always puts 5-7 amps into the batteries, even when they are "fully charged" and "floating."

One day we decided to keep closer tabs on each other. We had watched two DVDs the night before, and they had watched TV a bit

less, so the two battery banks were probably not equally discharged. They have a 23" flat screen HDTV with no surround-sound,

whereas we have a 26" flat screen TV with surround-sound and a large subwoofer, so we had probably drained our batteries a bit

more. However, I was shocked at how much more efficient their system was because of the tilted panels. It was clear to me that if

you want to operate your panels to their full potential during the worst winter weeks (December 1 to January 20), it is important to

have tilted mounting brackets and to orient your RV so the panels face due south. The mere "11% difference" between flush-

mounted and tilted panels that Wind & Sun had alluded to last summer must have been the average difference over the course of a

year. The difference in the weeks around the solstice is more like 50%. Also, few RVs have flat roofs; most flush-mounted panels on

RVs will have a 5-10% tilt in some direction.

December 8th was a very bright sunny day with perfectly clear skies. It was 13 days before the solstice (which occurs on December

21). Here are the readings from the two systems:

Time

Jensens

Us

360 watts

490 watts

Perfect tilt

Random tilt