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Old 05-22-2006, 12:03 PM   #1
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Best way to go solar?

I take delivery on a new (to me) 05 30' Classic next week. I'd like to add solar and would like to find the best route to go. I'm not a serious boondocker but would like to be able to enjoy an evening of television without running the generator (even though the Honda 2000 is very quiet).

I've been reading alot on the web about systems, panels/collectors, glass mat batteries, inverters and yadda yadda!!! And I've overwhelmed myself a little.

The Airstream dealer in Manteca California quoted me approximately $1200. for a system with two panels and 2 glass mat batteries and some sort of a controller.

What have you guys done for solar? Do it yourself? Had someone istall it?
And how do you figure how much system you need?

Thanks

Mike
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Old 05-22-2006, 01:23 PM   #2
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if you're going to watch TV or do other electronic things in the evenings, start by computing your required Watt-hrs. Typical lights are going to require 30 Watts, incandescent or flourescent, and you'll average two of these for 4 hours--240 Wh. The TV, if it's a small, efficient one, will need 70-100 Watts, also 4 hrs--400 WH. Water pump takes a lot, but runs for very short periods, so maybe 50 WH. If you're heater is running, I'd give it 50 Watts intermittently, say 100 WH. That's 740 WH, or 65 Ah. I use basic lead-acid batteries and they typically provide 95-115 Ah, but you can only use 80% of that safely without damaging the battery, so 78-92 Ah is what you'd have available from even a "primitive" battery. But that's only from, say, when you start cooking to when you bag it. If your heater is going to run during the night, oh oh, out of Amps. And only for a equinox day. For winter days you'll use more Wh, summer ones, less. Bottom line, two glass mat batteries will be more than enough.

Now you've got to charge them the next day. You can only count on solar from an hour after sunup to an hour before sunset (the high grazing angle makes the panels way inefficient). For the remainder of the day you're only going to average 50% of the rated output of the panels, unless you have them mounted in a sun-pointing tracker. Max ouput would occur at sideral noon and less on either side of noon. I also suspect that if you mount them on the roof, they will always be horizontal, so even a 50% average output might be optimistic.

Panels are typically 15W. You need to replace 800 Wh every day. On a winter day you'll have maybe 7 good sun hours, so each panel would give you about 100 Wh, less the 50% efficiency, resulting in 50 Wh. You'd need 16 of the 15W panels to do the job. On a summer day you'd need 10 panels. If you stand the panels on the ground at the optimum angle facing south, the numbers would drop to 10 and 7 panels, respectively.

I've made a lot of assumptions about numbers of lights and hours of working/viewing, but even if you're just one person, I doubt you'll get the number of [15W] panels required down below 5. Your dealer, on the other hand, may be providing much bigger panels.

BTW, this does not include any battery draw you need during daylight hours. At the low electrical loads you need in an Airstream, you could probably keep things going with only two hours of generator every 2nd or 3rd day. If that was even $4 at today's gas prices, that's about $700/yr, and no dragging out the panels every time you relocate. Also, the panels deteriorate over time--I don't know what the current life is, but in ten years the panels might have lost 30-50% of their solar conversion efficiency.

If you run this by your dealer and get vastly different numbers, I'd like to see the logic. My info is a bit dated and I'm thinking things may have improved significantly.
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Old 05-22-2006, 02:25 PM   #3
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Rich is reporting good results, so far. They installed 2 115-watt panels, and were able to recoup a 55ah evening's consumption in one day. normally, they consume 30ah or so per day...
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Old 05-22-2006, 02:38 PM   #4
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Thanks Zep & Chuck

Thanks for the info and link...I think I'm on my way to figuring out how to go. I appreciate it!

Mike
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Old 05-22-2006, 04:21 PM   #5
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We got the factory-installed solar setup on our new Airstream. The two panels are rated at 55 watts each and the batteries are the glassmatt type, which I believe are the only ones suitable for the charging characteristics of the solar cells and the device that controls recharging. I haven't made a study of the rate of recharge but was surprised to see over the weekend that I got readings as high as 6 amp hours just from sunlight passing intermittently through the trees in the Calaveras Big Trees Park. We're pretty efficient in our electricity use, I think, but it seems that with little effort we could go 5 or more days with normal California sunshine without seriously depleting the batteries.

Rich Luhr has what seems like double the capacity that we have: double the solar cells and double the batteries. Sounds like a serious boondocking setup, but probably overkill for your needs and mine.

The price you were quoted is just a bit more than we paid, but I suspect that our installation was easier because the newer models are already prewired for solar. I'm guessing that yours would require somewhat more work to retrofit.
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Old 05-22-2006, 05:19 PM   #6
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Thanks Mike

My trailer is an '05 and should be prewired for solar. Where did you have yours done and how much was it? I got my estimate from Manteca Trailer and Camper but it was off the cuff from a salesman there...might have be a WAG on his part.

I've learned you can spend a bunch of money on this solar stuff. I phoned a company in Oregon today and the woman quoted me a whole bunch of technical stuff with controllers and inverters and six volt batteries (6 of 'em I think) and the last thing she said before I passed out was $3000.00!! Yikes, I can buy a lot of gas for my very quiet generator for that kind of money.

Anyway, thanks again
Mike
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Old 05-22-2006, 05:33 PM   #7
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Mike,

Sorry, I should have been more careful and noted that you were referring to your new 2005 Classic, not the 1987 Sovereign. I think my dealer, RVs of Sacramento, is the smaller affiliate of the Manteca dealer with whom you are dealing. My understanding is that the more extensive work is done in Manteca. $1,200 sounds about right if right is the factory-installed price. With all the prewiring available and presumably the parts as well, the dealer should be able to do a creditable job. I can't really say how much ours cost because we bought new, picked all the options we wanted, then negotiated the total price.

You know that sunshine is seldom a problem for us in California or in most of the West for that matter. Carrying around a generator seems like a blow against the simplicity and self-contained nature of an Airstream, at least for modest electrical needs. If you require much more for running air conditioning or a microwave oven, then you'd have to jump up to the big Yamaha or Honda generators. Seems like a lot of stuff to lug around when communing with nature. Also, IMHO it seems like an affront to nature.
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Old 05-22-2006, 06:22 PM   #8
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If you are not into precise calculations and don't enjoy spreadsheets and research and analysis, try this empirical approach.

Don't plan on using solar for any heavy duty long term electical need like air conditioning. Short term microwave is pushing things for most portable solar systems.

Do some camping to figure out from experience how long your current RV battery will last when you use it the way you'd like to. Add batteries so you can go for at least two nights and three days on fully charged batteries. This is where the 'glass mat' or AGM batteries come in as you can put them inside without requiring the special ventilated compartment that normal wet cell batteries need. If you need more battery than your rig comes with, adding battery capacity is probably the biggest problem to solve.

For each 100 Amp Hour (typical group 27 RV battery) you have, plan on 100 watts of solar panel. Those can run $700 or so for a 100w panel.

Then you will need a 'controller' to connect between the solar panels and the batteries. Look for one that claims it is MPPT or maximum power point tracking. That runs about $200 or a bit more.

Installation and whatever in a pre-wired Airstream shouldn't take more than a couple of hours of shop time.

So a typical trailer with 200 Amp Hours Battery (which usually will meet the three day two night criterion in most cases) will need about $1400 in solar panels, $200 for a controller, and maybe $200 in labor plus a bit of hardware.

It is obvious the $1200 doesn't provide this amount of solar panels. That just means that charging the batteries is going to need more sun or only a smaller average use will be supported or that there is less headroom in what you can do.
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Old 05-22-2006, 06:57 PM   #9
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Sounds like I need to talk to the parts/maintenance department at the dealer and see what they can get. Leipper, what you say sounds most likely what I need. As I recall, the saleman was talking about two 50 something panels...I'm not sure...I wonder if I can buy all the components, the best state of the art stuff and have them install it. Thinking as I'm typing, that's probably my best bet to get a system to fit my needs, and not something the dealer throws together get it down the road.

And Mike, I'm with you on the generator, I have one and I'll use it if need be but my mission is to minimize if not eliminate the need....but I gotta have the microwave but that's only a few minutes of generator time when no one is sleeping.

Thank you all again for the great info.

Mike
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Old 05-22-2006, 07:35 PM   #10
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$1200 is not bad as long as they are quality components. That is about what Airstream asks for it installed at the factory. I went with the factory install. I am happy with it. it will get a work out later this week when I go to the Montana Rally.
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Old 05-22-2006, 08:30 PM   #11
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Get more knowledge before you leap

Flynmike:

I would recommend you learn a bit more about your probable 12 volt power needs before you leap into a solar system purchase, so you get the solar power system that will serve you best. Visit this web site as simply one of many similar web sites that discuss solar power:

http://www.rvsolarelectric.com/package.htm

and explore that web site. Don't stop with the one page I directed you to. I also highly recommend the book "RVer's Guide to Solar Battery Charging" by Noel and Barbara Kirkby, who are (or were) connected with the above web site. The time you spend now learning a bit more about solar charging systems and your probable amp/hour needs will pay dividends with a better initial purchase. I'm not sure a dealer parts department is the best place to seek advice about a solar system for your trailer. May all your days be sunny!
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Old 05-23-2006, 07:01 AM   #12
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You might be interested in my route at ...(lets see Iif I get this right)....http://www.airforums.com/forum...es-7632-3.html post #34.

The combination of good battery banks and solars are my preferance....
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