A short history of the sun

Several people wrote to me yesterday to say “thanks” for yesterday’s blog post on solar.   It’s amazing to me how much information there is on the Internet about RV solar power, and yet how little of it is actually useful or even accurate. So I’m going to write a little more about it today.


Wednesday was a less challenging day for solar power than I had expected. By afternoon the skies cleared up and we had good power generation for a few hours.  You really get the bulk of power between 10 a.m. and 2 p.m., no matter what time of year or latitude, if you have fixed panels that always face directly upward like we do.  (People with tilting panels have a big advantage, because they can capture light at a more direct angle during the morning and late afternoon. I’d like to install those on the Airstream but so far I haven’t found a practical and cost-effective solution.)

The batteries started the day down 34.7 amp-hours.  I used the laptop for eight hours, and Eleanor used hers for about an hour, plus we recharged phones and camera batteries.  Even with this relatively heavy load, the batteries ended up at -15.4 amp-hours (a net gain of 19.3 amp-hours).  When you figure in the power we used while the sun was shining, we probably generated about 40-50 amp-hours during the day.  Not bad for a half-cloudy day.

I give these statistics as guidelines of how things might work for you, but it’s important to keep that the bottom line of solar use is that every situation is different. The key variables are: sun angles (time of year, latitude, time of day), cloudiness, panel generating capacity, and storage capacity.  A lot of the websites go on and on about wiring losses and other electrical engineering details, but in real life a single leaf on your panel can have a much larger effect on power generation.  Don’t get hung up on whether your wires are big enough if you haven’t first tried cleaning the glass.

Because there are so many variables, it’s impossible to answer the question I get all the time:  “Is my system big enough?”   Big enough for what?  From trip to trip, I never know how much power we are going to generate in advance (I’d be a great weatherman if I could).  The best description I ever heard was that “solar makes your batteries bigger.”   Think about it that way and don’t worry about having unlimited power — even with a generator, it’s an illusion.

I’m just happy that we can camp for long periods without power connections, at least in the summer.  We’ve been here at Horseneck Beach since Saturday.  Just for comparison, if we had the original factory batteries and no solar panels we would have run out of power on Monday.

Now, since I mentioned generators, I feel obliged to explain why people who have generators often are seriously deluded about what’s really happening when they use it to “re-charge” the batteries. It really doesn’t work, at least not with the standard gear that comes with most trailers.

The reason is based on the fact that batteries will only accept re-charge at a certain rate.  As they get more charged, they resist, and so the rate of charge declines.  It doesn’t matter how big your generator is; you could plug that battery into a nuclear power station and it still won’t charge any faster.   A “smarter” charger will do better than the really dumb 2-stage chargers that seem to be installed in most trailers, but only to a point.

For example, your batteries might accept a charging rate of 15 amps (DC) when they are really heavily discharged, and 5 amps when they are 25% discharged, and 1 amp when they are 10% discharged.  If you’ve got an 80 amp-hour battery bank, getting from 90% to 100% charge could take eight hours or more.  That nice quiet 2000-watt generator you use will produce a whopping 150 DC amps at its normal maximum output rate, which is obviously way more than the batteries will accept at any given time.  The rest of the power is wasted, unless you are running the microwave or some other AC appliance while the generator is running.

The other problem is that the factory installed “battery monitors” are almost always cheap-o versions that guess at the batteries’ state of charge by measuring voltage.  This is incredibly inaccurate, especially those lousy units that show the battery condition using Red, Yellow, and Green LEDs.  Would you drive a car with a gas tank gauge that just showed red, yellow, and green?  Even worse, these units will show Yellow when there’s a heavy power demand even if the batteries are full, and they will show Green when the batteries are actually quite discharged but have recently been charged just a little.  Imagine that the car’s gauge went to Yellow every time you pressed the accelerator.

Try it sometime.  Use your batteries for a day or two, until they show Yellow constantly.  Then plug in for 30 minutes, unplug, and watch as (miraculously!) the monitor reports Green or “100%”.  Don’t believe it.  That’s what is sometimes called a “surface charge.” It’s a symptom of the battery monitor being fooled because it measures voltage.  The voltage pops up for a short time after charging, but it won’t last.  To get an accurate view of battery charge using voltage, you need to let the batteries “rest” (no drain, no charge) for at least an hour.  That almost never happens in a camping situation.

So here’s the scenario I see all too often:  After a day of camping, the owners decide it’s time to charge up the batteries.  They fire up the generator, plug in, and let it run for an hour or two.  The voltage-based battery monitor says all is well, so they turn off the generator and go to bed secure in the knowledge that they are “all charged up!” Except they really aren’t.

In two hours, the best that generator is can do is pump in maybe 10 amp-hours, if the batteries were moderately discharged to start.  Rather than being “100%” the reality is that if they started at 70%, they might now be at 85%.  So the next morning, the campers wake up and use a little power for the water pump, and by 10 a.m. they are amazed to see that they are back in the Yellow zone.  What happened?

So they plug in the generator again, and this time they run it for three hours, getting up to 88% charge.  At this point the batteries are really resisting further charge, so only about 1 or 2 amps of the 150 amps that generator can produce is actually getting into the batteries.   The next day, same problem — the battery monitor says they are still stuck in the Yellow zone.

Solar has a huge advantage here.  A steady all-day charge will get your batteries up to 100%. It’s like the turtle and the hare.  With batteries, slow and steady wins the race. If you have both a generator and solar panels, use the generator only when the batteries are heavily discharged (for an hour or so in the morning, for example) to get the bulk charge done quickly, and then let solar finish the job over the course of the day.

If you only have solar, keep in mind that during the morning and mid-day, moderately or heavily discharged batteries will probably accept every amp the panels can generate.  Then the charging rate naturally slows down.  In our case, by mid-afternoon the batteries are usually in the 90-100% range, and the charging rate has slowed to perhaps 1 amp.  If the panels are still generating 5 amps, we have surplus power, and so that’s the time of day we plug in all of our rechargeable accessories like phones, cameras, Kindle, laptops, etc.  This strategy takes maximum advantage of the power being generated.

Another good time to use a generator is when power demand is high.  It’s much easier to avoid using battery power (by being plugged into the generator) than to try to recharge battery power later.  So if you have small batteries, use the generator in the evening when you are making dinner, and any power consumed will be supplied by the generator.

Good kite flying weather

The wind is back at Horseneck Beach campground.  The reservation website did warn that “sites can be breezy.”  People who come here regularly seem to be prepared for it, as I see a lot of kites and streamers attached to poles.  The big round rocks from the beach make handy weights to keep your belongings from blowing away, too.

horseneck-beach-emma-kite.jpgSo we broke out the kite that we’ve owned for many years and hardly ever flown.   Eleanor admits to being a hopeless kite pilot, and Emma has surprisingly little knowledge of kites, so there was some initial confusion, but eventually up it went, and it flew very well … until the inevitable crashes in the wild rose bushes. The kite survived to fly another day.

We didn’t do much else.  In the morning, we cleaned up the Airstream and relocated it to another campsite. (We’ve booked two more days here, but that meant we had to switch sites.)  I was tied to the computer the rest of the day, editing articles for the upcoming Winter 2010 and Spring 2011 issues.  Still, working near the beach on a beautiful sunny day gives the opportunity for very pleasant breaks, walking along the seashore or just enjoying the sun and salty breeze blowing through the trailer.

We had thought that in the evening we might hit one of the local restaurants for another seafood dinner, but of course being post-Labor Day, all of the tourism-related businesses are closing or reducing hours.  We settled for some interesting takeout from the local grocery and a movie at home.  It has gotten very quiet here, and that’s nice.

Solar report:  Since not much is happening, I’ve got an opportunity to talk a little more about solar.  Forgive me if this topic bores you, but I get a lot of inquiries from blog readers, so I know there is a need for real-world information.  Yesterday was full sun again, and with our 230 watt panel array, at this time of year (when the sun angle is still fairly high), we really can’t store all the power we generate.

We started Tuesday morning with a 36.0 amp-hour deficit, which is fairly normal as a result of using lights, water pump, and laptop the night before.  During Tuesday I was on the laptop for at least six hours, consuming about 9-10 amp-hours in total, and Eleanor used probably another 3-4 amp-hours charging her laptop.  Still our batteries were at 99% by 5 p.m., indicating that we generated more than 50 amp-hours during the day.

That’s all well and good while the sun shines, but the other half of a solar charging system is storage.  You’ve got to have battery capacity that is matched to your power needs and the capacity of your panels.  Long-time blog readers know that since January 2010 we have used a single Lifeline GPL-4D, which has a rated capacity of 210 amp-hours.  Today (Wednesday), we will see that half of the system put to the test.  The forecast is for gloomy skies and rain — in fact, it just started to rain as I am typing this.  Under the rain cloud, our power generation has been cut from 8-9 amps when sunny to a miniscule 0.8 -2.1 amps (depending on the thickness of cloud).  Essentially, at this moment we are generating only enough power to make up for the parasitic drain that is inherent in all modern RVs.  So, under those circumstances our power supply would be entirely reliant on the battery.

We started today with a deficit of 34.7 amp-hours. If we generate no power today, I would expect the battery to be drained by a further 20-30 amp-hours by 5 p.m., just as a result of my laptop use and normal parasitic drain. (Parasitic drain comes from the circuit boards and always-on electronic modules in the stereo, refrigerator, thermostat, propane leak detector, etc., and totals about 0.5 amps per hour.)  Tonight, we will use another 25-35 amp-hours, which means we could end up tomorrow morning with a deficit of 80-100 amp-hours.

Ideally you never want to discharge the battery by more than 50%, which means that at 110 amp-hours we need to either find some sunshine, or plug in to power.  If we are not cognizant of our power budget today, and the weather continues as it is, we’ll be up against that limit tomorrow.

Now, there are three practical responses to this.  (1) We could add more battery capacity.  A second Lifeline GPL-4D battery would double our capacity, but at the cost of about $500-600 and 135 pounds of added weight.   Also, given the rating of our solar panels, we would be hard pressed to recharge a deficit of 110 amp-hours under typical conditions.  Certainly we’d never be able to do it in a single day.  So our batteries and panels would not be well matched, although that’s not a big problem.

(2) We can plan ahead.  For example, we know that tomorrow we are pulling out of the campground and relocating.  There’s a very good chance that we will get at least partial sunshine while we are towing, which will yield power for the batteries.  (The tow vehicle does not add a significant amount of power to the batteries while towing, by the way — that’s sort of an urban myth.)  Or, if we know we are going somewhere that we can plug in, we don’t need to worry about reaching our power limit tonight.

(3) We can cut our power usage.  I could relocate to a coffee shop somewhere and use their power for my laptop.  I could take the afternoon off.  We could use only the LED lights in the trailer tonight.  We could use the campground showers to avoid using the power-hungry water pump in the trailer.  I find that a lot of people hate conserving because it makes them feel deprived, but we don’t mind so much.  If I’m “forced” to quit work early, I can live with that.

But I probably won’t get that excuse.  That’s because, in the real world, the weather changes.  It probably won’t stay cloudy all day.  Even as I’ve been typing this, the rain has stopped and some breaks have appeared in the skies.  Right now we are generating 6-8 amps, which is a very healthy rate for recharging the Lifeline. Despite fluctuations, we should generate at least enough power today to offset my laptop use.

It’s important to consider this, because people who don’t like solar power tend to invent worst-case scenarios to “prove” that it is impractical, and those scenarios often include cloudy skies.  That’s like proving generators don’t work when the gas tank is empty.  Especially in the northeast and northwest, it is quite possible to have extended cloudy periods that make solar impractical, but even in those cases it is useful.   The point is not to have unlimited power capacity.  For us, solar is a tool to enable us to camp peacefully while silent, maintenance-free power streams into our batteries automatically and extends our time in a great spot like this one.

Cliff Walk, Newport RI

We awoke on Labor Day to find a peculiar calm following the storm.   In a radical change from the day before, the ocean’s fierce winds and thundering waves had been replaced by a placid waveless bay, with no breeze at all.  All across the campground, the people who had wished to spread out for the long weekend finally got their chance, and out came the vital camping accessories: awning, folding chairs, outdoor rugs, colorful umbrellas, rope light, telescope, flags, tiki torches …

Being light-weight travelers as much as possible, we don’t carry a lot of accoutrement.  We also don’t spend a lot of the time at the Airstream, when there’s exploring to be done.  I think that’s a difference in traveling philosophy.  The folks who are out here for the weekend want to establish their territory and create a mini-palazzo  by the sea.  We are not the types to sit under the awning and admire the ocean for very long, and whenever I set up the awning it seems that the wind will kick up or a thunderstorm will come by.  So our site remains bare relative to the festive campers nearby.

Instead of admiring the calm sea, we made plans to head to nearby Newport RI, to hike the famous “Cliff Walk” along the magnificent “summer cottages” (mansions).  These mansions were built with Gilded Age money from railroads, oil, and other industrial concerns when income tax didn’t exist and monopolies were allowable.  Many of them are open for tours, and along with the pleasant streets of central Newport and the Cliff Walk, make for an interesting day.  When we lived in Massachusetts we used to come down here regularly, and I used to lead bicycle tours right through the city, but Eleanor and I just calculated that we haven’t been to Newport in about 20 years.


Newport is more pleasant to navigate by bicycle, in my opinion, especially if you want to hike the Cliff Walk. Parking is a problem at peak times, and it doesn’t get more peak than Labor Day.  Luckily we snagged a space in the parking lot at nearby Easton’s Beach (above), which is just a short distance from the formal end of the Cliff Walk.

newport-eastons-from-walk.jpgFrom there, it is 2/3 of a mile to the first exit of the Cliff Walk at Narragansett Avenue.  The trail winds above the edge of the sea and just below the elegant houses.  Some are open to the public,  a few have become inns or restaurants, and the rest remain private.  All told, you cross the property lines of 64 owners if you traverse the full 3.5 miles of the Cliff Walk.

At times the trail reminded us of the hiking trails along Lake Como (Italy), with cut stone and meticulously built retaining walls.  At other times the trail is more modern, and at still other times it is rustic and rugged like some hikes in Acadia National Park (Maine).  There’s no time, however, at which the trail is anything less than beautiful.

From the back the houses protect their privacy with tall hedges and fences.  But you can take one of several exits up side streets to drop in on the ones that are open for tours, like the famous “Breakers” pictured below.


The idea behind these “cottages” was that super-wealthy New Yorkers could exchange the heat of summer for the breezes of the oceanfront.  In the 19th century you didn’t have air conditioning no matter how wealthy you were.  The elite would hold conduct an elaborate social season in their American castles while admiring the view and the grounds.

newport-cliff-walk1.jpgNow of course, anyone can do the same thing in a smaller way.  The palazzos by the sea are out in great numbers here at Horseneck Beach, for the price of $15 per night.  We don’t have ballrooms large enough for 400 of the “best” people, but on the other hand we can still live quite happily listening to the waves, and we don’t need a gardening staff.

Solar report:  Full sun again on Monday, and batteries were at 100% when we returned at 7 p.m.  With more sun predicted, and work resuming on the laptop, we’ve let our power budget rise.  At 8:00 a.m. Tuesday batteries were reading -36.0 amp-hours. Even with a few hours of laptop use I expect nearly full power by mid-afternoon.  We don’t usually get a lot of use out of our solar panels while on the east coast, but with no trees at Horseneck and plenty of sunshine this week, living within the budget of solar power has been easy.

New Bedford, MA

The high and rough seas continued on Sunday at Horseneck Beach.  Swimming was impossible, as waves crested well over six feet and the winds were fierce.  We tried to go for a walk along a short causeway near the campground, but the wind out there was even more ferocious and we eventually turned back.  It is lucky that there is little sand on the beach here, or it would be a stinging experience indeed to be near the water.  We haven’t seen wind at the beach like this since we were waiting for the ferry to North Carolina’s Outer Banks.

Still, it has been nice here.  The view is still spectacular, the nearby town of Westport Point is beautiful, and we don’t often get to park the Airstream right by the seashore — waves or not.  The sound of the wind and waves masks the purr of generators at adjacent sites, and blows their campfire smoke inland and away from us.  (I can’t figure out how anyone can keep a fire going in this wind, but a few people have managed it.)

Given that this wasn’t the best beach day, we decided to explore the surrounding area.  Inland, the wind is barely noticeable. After a very leisurely morning in the Airstream, we wandered into the village on the assumption that every good beachfront area in Massachusetts has a place that sells fried clams. We were pleasantly rewarded with the discovery of the Handi Hill Creamery, which sells both fried clams and an incredible range of ice cream flavors. That stop and the resulting picnic at the outdoor tables took up a good chunk of our day, and it was well worth it.

A long time ago, I used to lead bicycle tours around Massachusetts, and one of our signature trips was up to the North Shore where we’d stop in at a clam shack and pig out.  I assured all tour participants that they could eat a fried lunch, because they were going to cycle 40 miles that day and burn it all off.  (This theory worked well except for those who failed to recognize that eating a lot of grease before completing the final 20 miles of a bike ride can be hard on the stomach.  You do need to show some moderation.) Puttering up in a car and doing the same thing yesterday gave me some small unease, as I felt I hadn’t “earned” the meal, but I got over it pretty quickly.

new-bedford-whaling-museum.jpgNot far from Westport Point is the former “whaling capital of the world,” New Bedford.  Although whaling is now regarded as an international crime, New Bedford has not shied away from its history, and in fact hosts a national park site and a very good Whaling Museum in the center of the historic cobblestone/gas lamp district of town.

I can recommend the museum if you’ve got 1-2 hours to explore it.  The collection goes far beyond whale bones and harpoons — there’s some great ship models, modern science about whale research, and ancillary collections about life aboard ship and life back at home during the era.

From the museum you can walk a self-guided tour through New Bedford’s working waterfront and the downtown.  Eleanor and I were surprised to see how much architecture of the 18th and 19th century has survived in downtown New Bedford.  This makes exploring the city an extremely photogenic experience, for those who appreciate urban landscapes and historic buildings.

Sunset seems to be coming very early now.  It’s a reminder that we are still fairly far north and fall is coming.  From our spot on the beach it’s hard to believe that in three weeks the leaves will be turning and 80-degree days will be just a fond memory.  But not for us.  If all goes well, we will follow summer all the way down the east coast to Florida.

Solar report:  with full sun, the battery was recharged to 99% by 2 p.m. That means we have plenty of excess capacity, so last night we were considerably more generous with laptops and lights.  At 8:30 a.m. this morning, the battery was at -28.9 amp-hours again and with full sun in the forecast today we expect the battery to be fully charged this afternoon.

Horseneck Beach State Reservation, MA

The Airstream is rolling again!

Our tour this fall will bring us down the cluttered East Coast, with stops in Massachusetts, Connecticut, Pennsylvania, Virginia, North Carolina, and Florida (at least).  The full itinerary isn’t yet worked out because we like to leave in flexibility, so I expect a few other stops will pop up as we slide south.  The plan calls for us to get to Florida by early October.  We’ll hang around there for a few weeks, then start the western leg back to Arizona in November.

washing-airstream.jpgOf course, with the Airstream sitting in a driveway under trees for the past three months, we’ve had some prep work to do this week. Mostly it was a matter of having to evict the spiders, who have been busy covering the Airstream in webs, and cleaning the roof.   Normally I don’t sweat the dirt on the roof, but in this case we knew we’d be camping without power hookups and so I had to get up on the roof and at least clean the solar panels.  Once I saw the condition of things up there, it was obvious everything had to be scrubbed with a brush.  I have never seen a roof so incredibly filthy. We had leaf mulch, bird droppings, rotting twigs, some sort of mildew or mold, spider webs, and heaps of leaves.  (The discolored water you see coming off the roof contains no soap — that’s just the gunk I’ve scrubbed loose.)

The junk on the roof was blocking the proper drain channels for rainwater, and it made examination of the caulk impossible, in addition to disabling the solar panels.  So it’s a good idea to get up there once in a while to clean and inspect, but you do need to be exceptionally careful on a wet Airstream roof.  I didn’t use soap because I didn’t want to slip off.

The other pre-departure tasks including washing the entire trailer, vacuuming all the window screens and cleaning the windows, cleaning off the last of the adhesive from our former “Tour of America” sticker, greasing the hitch, adding air to the tires, dusting the window sills (it’s amazing how much dust they gather), cleaning the roof vent screens, and cleaning the interior.  After a few weeks in Vermont we always notice that the interior gets a sort of funky wet-dog smell.  Laundering all of the soft goods (blankets, sheets, towels, rug) and wiping down all the interior surfaces with orange cleaner eliminated that.

Eleanor spent a few days sorting through Emma’s things, because every time we move, she has grown taller and half her clothes no longer fit.  Likewise, she reads about 15 books a month, so those had to be sorted too.  23 pounds of her books were shipped to home base in Arizona, and another 10 pounds or so were given away.  It’s not the weight so much as the volume of these books — there’s just no space to store a kid’s library in our 240 square foot home!

lake-champlain-emma-hobie-tip.jpgHurricane Earl came up the east coast on Thursday and gave us an unexpected extra day in Vermont.  The state of Massachusetts closed all the seaside campgrounds, which included Horseneck Beach State Reservation, our planned destination for Labor Day weekend.  The closing was precautionary, and fortunately Earl left no significant damage at Horseneck.  But that left us in Vermont on Friday, with good sailing conditions, so Emma got to go ride the trapeze on Uncle Steve’s Hobie Cat again.  She’s become (mostly) fearless about this sort of sailing, since they’ve been teaching her the ropes all summer long.

lake-champlain-eleanor-chase-boat.jpgCarolyn took her own Hobie out, and Eleanor and I followed in the chase boat (Boston Whaler) to snap pictures.  If Earl hadn’t come up the coast we would have missed this.  If the Massachusetts Dept of Conservation hadn’t closed the campgrounds, we would have been camping in the rain and wind instead.  So in a lot of ways, it was a good last night in Vermont on Lake Champlain.


Saturday we arrived at Horseneck Beach.  It’s one of those exciting east coast campgrounds that runs right alongside the ocean front, with constant wind and (thanks to Earl) high surf.  The moment we stopped the car and opened the door, we were buffeted by a fresh breeze with that unmistakable smell of salt and seaweed that always make me think of lobster.   It felt great.


The wind is very strong.  We won’t be putting out the awning.  In fact, our campsite runs parallel to the rocky beach and the Airstream is being hit by the breeze broadside.  I put the stabilizers down rather firmly to keep the trailer from rocking too much.  We can’t leave anything outside, lest it blow away.

Within minutes of being parked, the side of the Airstream was coated with a fine spray of salt.  Even opening a window on the windward side results in salt-laden air blowing in. The waves are about 150 feet away, and we can hear them pounding on the shore all day and all night.  I think the last time we heard that wonderful thunderous sound, we were sleeping in a parking lot on St George Island (FL), nearly four years ago.

The beach here is composed entirely of round rocks about 4-8″ in diameter.  They roll and clatter into the undertow with every wave with the sound of a thousand crabs all clacking their claws at once. Between our site and the beach is a barrier of saltgrass and wild beach roses, with a narrow path through it.  Emma has discovered ripe rose hips growing plentifully.

Our arrival was not completely ideal.  The park ranger was off doing patrol when we arrived, so we followed the instructions and parked ourselves in our reserved spot.  This was a little tricky due to the narrow pavement areas in the sites, and we needed two leveling blocks on the sea side of the trailer to make it level.  With the wind making communication difficult, it took a little more effort than usual, but in about 15 minutes we were set up, unhitched, and ready to settle in.  Then I went back to the ranger station to check in, and discovered that we were in the wrong site.

After driving 300 miles, I was a bit tired and it was already five o’clock.  But there was nothing to do about except break camp, hitch up again, and push the Airstream backward about fifty feet to the correct site, then repeat the entire performance of setting up again.  It was about six by the time we had it all done.

horseneck-beach-office-view.jpgWell, these things happen.  I can’t pretend I was happy about it, but I knew that once the job was done we could settle in and do basically nothing for the next two days.  We have a few ideas of what we might do today and tomorrow, but it is Labor Day and everyone knows that Americans celebrate Labor by doing nothing laborious.  So I don’t plan to do any work this weekend, other than a little blogging.  But if I did, could I ask for a better office window view?

Solar power report.  There are no hookups in this park, so we are using only solar power.  We started yesterday with full batteries, of course, and at 8:00 a.m. this morning our Tri-Metric battery monitor reports -28.3 amp-hours.  That’s about average for us for one night, with no furnace use and minimal laptop use. Today we expect full sun all day.