Solar Tutorial Part II – Small Upgradeable RV Solar Power Systems

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<– Solar Tutorial Part I – Basic Concepts
Solar Tutorial Part III – Full-timer Kits –>

Designing a solar power system for your RV depends entirely on how you plan to use your RV.  Are you RVing in summer or winter, or both?  Are you staying in it for a week or two at a time or for several months at a time?  Do you want to use a laptop for an hour or so a day, or do you need to camp out on it for 4-8 hours at a time?  Do you hit the sack after an hour or so of watching TV or do you want to plunk down in front of it with a cocktail and stay planted there until after midnight?

RV solar panel on the ground

We didn’t install the panel on the roof at first. Silliness! Install it on the roof so you don’t have to think about it!

As a general rule, more solar power is better.  It is really awesome to have so much power that you never need to think about it.  If you are planning to live in your RV for extended periods of time, want to use big appliances a lot and don’t want to be dependent on electrical hookups, get a big full-timer’s system right off the bat.

However, if you are just weekending, vacationing, and living largely outdoors, get a small system.  You’ll quickly learn what you can and can’t do.  It is very easy to upgrade if you find you need more.  Upgrading is mostly a matter of adding more and bigger parts.  Not too many parts have to be swapped out.

RV solar panel installation - wiring the panel's junction box

Mark connected the cable to the panel’s junction box before hoisting the panel onto the roof.

This page describes a “starter solar setup” which is good enough for heading off into the woods for a month or two of simple living in the summer.  We used a system of this size for a full year, boondocking (dry camping) for months on end.  We typically used the laptop or TV or stereo just 1-2 hours a day.  We went to bed 2-3 hours after sunset.

In the summer it was fully adequate for those kinds of light electrical needs.  In the winter there was so little sun that we had to be very conservative.  We used oil lamps at night, and we supplied extra charging for laptop, toothbrush, camera batteries etc. by charging them in the truck while driving around, using a portable inverter plugged into the cigarette lighter in the truck.

A Small Solar Setup:  150 watts of solar power with portable 150 & 300 watt inverters

If you are going to dry camp in your RV in the summer, you don’t need an big solar power system.  You will be busy around the campfire at night rather than watching hours and hours of TV.  You will be using your RV when there is abundant sunshine, and you probably won’t spend too many hours on your computer.  Here is a very simple solution that will be sufficient for as much as a few months of simple living in summertime:

1 150 watt solar panel ($220)
1 Morningstar 10 amp charge controller ($60)
1 Portable 150-300 watt modified sign wave inverter ($30)
10 gauge wire that is rated for outdoor use ($150)
2 12-volt batteries wired in parallel ($150 for that second battery, as your RV should have a battery already)

Total cost:  ~$650
Wild guess at an installer’s fee:  ~$400

Installation

RV solar panel installation on a fifth wheel

Cardboard covers the panels (shown here on our big full-timer’s installation) so they aren’t live

Installation isn’t too difficult if you are willing to scramble around on the roof a bit:

(1)  Install the solar panel on the roof.

While working with the panel, keep it covered so it isn’t producing electricity.  One easy way to cover it is to cut part of its cardboard packaging to size and tape it on.

Mark drilled holes in the roof and used anchors for the screws in places where the panel couldn’t be screwed into a roof truss.  He jammed Dicor lap sealant into the holes before putting the anchors in, then ran the wire and then put more Dicor on the whole works after it was screwed down.

RV solar panel installation on a travel trailer

Mark used lots of Dicor roofing lap sealant

If there is a chance you might eventually want to use your RV in winter, install the panel on tilting brackets so you can tilt the panel towards the sun.  It isn’t necessary to tilt the panel in the summertime, but it can be a huge help in the winter when the sun rides very low in the sky and doesn’t shine down on the panel but actually shines kind of across it from just above the horizon.  Tilting the panel towards the sun might give you an extra 25% of total charge for the day in the wintertime.

When you have tilting brackets, you have to climb up on the roof to tilt the panel each time you set up camp — and you have to remember to climb back up again to lower it down before you drive off.  If you don’t think you want to do all that scrambling around on the roof, skip the brackets (and consider getting two panels instead, described in Part III of this tutorial).

(2)  Install the charge controller inside a hatch near the battery compartment.

(3)  Run the wires from the panel to the charge controller

Connect one end of the wire to the panel (there are screws in the junction box on the panel that you screw the wire to).  You can use duplex wire or two runs of single conductor wire for the positive and negative leads. If the refrigerator is not in a slide-out, run the wire down through the refrigerator vent to the battery compartment.  Otherwise, run the wire down along the outside of the grey or black water vent pipe.

Taping the wire to a metal snake and snaking it down behind the fridge really helps.  We snaked ours down inside a piece of PVC pipe that we used as a kind of conduit to keep the wire away from the back of the fridge.  If you do that, make sure the PVC pipe is quite a bit bigger than the thickness of the wire so you can get it through easily.

RV solar panel installation crawling on the roof

Our lightweight Lynx trailer did not have a “walk-on” roof, but Mark used a telescoping ladder and crawled around to install the panel

You can also use the MC4 connectors in the solar panel’s junction box and use solar power cable that has MC4 connectors pre-installed

At the charge controller, connect the wire coming down from the solar panel to the input side.  Run a second wire from the output side of the charge controller to the batteries.  It is best to crimp eyes on the ends of the cables.

(4)  Remove the cardboard from the panel.

 

You should see an LED light on the charge controller turn green to indicate that it is charging.

300 watt inverter for an RV solar panel installation

Use small, portable inverters plugged into the RV’s cigarette lighters for the TV, laptop, etc.

Now your panel will start charging your batteries all day every day.  It might even start charging them before you get out of bed in the morning!  They will charge faster if you are in full sun.  Just a little shade on the panel (like a single tree branch across one corner) will cause them to charge much more slowly.

(5)  Use your AC appliances

Plug your portable inverters into whatever available cigarette lighter outlets there are inside the RV.

Whenever you want to watch TV, DVD’s or use your laptop or charge your camera batteries or toothbrush or whatever, plug the appliance into an inverter, turn the inverter on, and use the appliance as you would at home!!

RV solar panel installation on a travel trailer - completed

A successful morning’s work – the panel is permanently installed!

(6)  Add a second 12-volt battery to your battery box (this could also be Step 1, it doesn’t matter). 

The battery is your energy storehouse.  You add energy to it when you charge the batteries and you remove energy from it when you use your appliances and lights.  Think of your batteries as being a big kitchen sink.  You fill the sink with water (charge the batteries) by turning on the faucet.  You drain the sink (when you use your appliances and lights) by removing the drain plug.  The goal is to keep the sink at least 2/3 full all the time.  After a day of sunshine, as the sun is setting, your sink should be full.  After an evening of watching TV and computer work, your sink should not be less than 2/3 full (batteries don’t like to be drained until they are empty).

Group 24 deep cycle 12 volt battery for use in an RV solar power system

Add a second Group 24 12-volt battery in parallel

So you have to balance the size of your faucet (the total wattage of the solar panels), the size of your sink (the total amp-hour capacity of your batteries) and your appliance usage (how often and for how long you remove the drain plug) to make sure you don’t drain out more than you can fill up on a sunny day.

Most RVs come with a single Group 24 12-volt battery.  These typically store about 70 amp-hours of energy.  Adding a second Group 24 12-volt battery will double the size of your “sink” to about 140 amp-hours of energy.  As a very general rule of thumb, the total watts of your solar panels should be comparable to the total amp-hour capacity of your batteries.  With 140 watts of solar panels in this system, it makes sense to have two 12-volt batteries to give you 140 amp-hours of battery capacity.

Make sure there is room in the battery compartment for a second battery, as some RVs don’t have room for one.  When shopping for an RV, if you plan to dry camp a lot, make sure the battery box can hold two 12-volt batteries.  Wire the two batteries together in parallel.

 To learn more about batteries and battery charging, read this article:

RV and Marine Battery Charging Basics

And that’s it for this whole system.  Very very simple.  The only limitation to this system is that you need to keep your TV/laptop usage fairly light and you cannot use your microwave, toaster, hair dryer, vacuum or air conditioning unit.  However, it is a great starter setup to get your feet wet and learn to live in a solar driven home on the road.

Monitoring Your Batteries

Fluke snap-on multimeter voltmeter

A multimeter can help you monitor the batteries

The easiest way to see how your batteries are faring is to use a multimeter and measure the voltage.  We use a Sperry clamp-on meter that has jaws that can wrap around wire so you can measure the amperage flowing through the wires, if need be. The Fluke meter is an even better unit because it is true RMS.

Monitoring the battery voltage with a multimeter is not scientifically accurate, because batteries have personalities and memories and only tell the truth about themselves when they have not been under load for a long time and have been cleaned of their surface charge.  However, checking your batteries’ health with a multimeter can still give you a good indication of how they are doing.

Early in the morning, before the sun has gotten over the horizon, measure the voltage between the battery terminals.  If it is 12.3 or higher, you’re okay.  If it is lower than that, go outside and play and leave the indoor appliances alone for a day or two (and hope for sunshine).  If that’s not possible, start thinking about finding a place to plug in.

Likewise, check out the voltage sometime right after sunset before you get the TV or laptop going.  If it is 12.6 or more, you are golden.  If not, then rethink your evening’s activities a bit.

A Portable Solution with NO INSTALLATION NEEDED!!

Folding RV 12 volt solar panel suitcase for_

Portable solar panel kit that folds into a hard shell suitcase!

One very slick option for adding a small solar power system to your RV without going through the trouble of installing the panels on the roof is to get a folding portable solar panel kit. These wonderful kits are pairs of panels that are hinged together on the long side, and they fold together to form a hard shell suitcase that has a handle for easy carrying.

The beauty is that the panels are naturally protected when you store them away, and they have built-in stands that support the panels at a tilted angle when they are set up, so you can aim them south for maximum efficiency.

They come with a small solar charge controller so the batteries don’t get overcharged, and they have alligator clips that make it easy to clip the leads onto the battery terminals.

This is not an upgradeable system, but if you are simply looking to enjoy some dry camping and boondocking in your RV and want a little solar boost for your batteries, this is an all-in-one 120 watt system that will get the job done!

Most portable suitcase kits don’t come with an inverter, so remember to buy that too!

Most of the components for an RV or marine solar power installation can be purchased at Amazon.

Shown here is a complete "weekender/vacationer" kit (far left), a small charge controller (middle) and a small inverter (right). More comprehensive listings of each component type can be found at the following links:

Purchases at any of our Amazon links help keep us going. But don't buy anything yet. Finish the tutorial first!

 

Part III of this tutorial describes ways this starter system can be upgraded to get a little more power. Return to Part I here.

Solar Tutorial Part III – Full-timer Systems –>

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FURTHER READING – RELATED ARTICLES

SOLAR POWER OVERVIEW and TUTORIAL

BATTERIES and BATTERY CHARGING SYSTEMS

LIVING ON 12 VOLTS

 

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