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Loki

Boondocking with 1750 Watt of Solar Power on a small 5th wheel

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I love boondocking,and I hate generators. Recently, I sold my 37 ft 5th wheel and bought a 29 ft Arctic Fox 27-5L, because I was fed up with being stuck in tight National Park and State Park campgrounds. When I climbed on the roof for the first time and saw how cluttered the roof was with exhaust pipes, hoods, AC unit etc, and considering a usable roof length of less than 25 ft, I all but gave up on the dream of installing a meaningful solar power plant  on this roof. But after taking exact measurements of the roof and the obstacles, and realizing how far the solar panel industry has come in terms of power output per square unit, I started some serious research. And came up with the solution of installing  5 of  350W monocrystalline JA Solar panels. They are about 38"x79" big and cost me less than $200 per piece (plus freight), which is a steal deal compared with what other dealers charge.Because several roof obstacles are about 40" away from the roof edge, I was able to squeeze 5 of these panels on the roof (see attached pic). Of course, mounting them so close to the edge and to hoods etc. was pretty challenging,and I had to use slightly different methods to fix the panels to the roof, depending on their location. Since no solar mounting hardware available on the market could be used because of the tightness, I devised my own, relatively simple method by using pairs of slotted aluminum angles in each of the four corners of a panel. Each angle was about 10" long; one was screwed to the panel, the other one on the roof in a way that aligned the slotted sides of the angles so that they could be bolted together (see pic). One of the panels had to be raised about 7" above the refrigerator exhaust hood, but that was the only more complicated construction (see pic). 

The 10 wires from the panels are connected in a combiner box that sits atop the hole that I had to drill right above a wall that is already used as a wire raceway. I chose AWG 1 wire from the combiner box to the solar controller (that sits in the front compartment), which probably is an overkill, but the cost difference is negligible compared to the overall cost of the project. 

In a subsequent post, I will talk about the installation of the solar controller, a 4000W inverter, 2 Tesla battery modules, and the necessary control and protection circuitry. And, of course, about the practical experience with running the entire coach off grid, with water heater, AC, microwave, toaster, hair dryer and all the other power hungry gadgets.

 

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One of things I learned with heating water off solar power is that I could turn on my circuit breaker for 10 minutes which heated my 2.5 gallon water heater perfectly for taking a shower. Not having to add cold meant no wasted water down the drain.

Linda Sand

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There are electric water heater elements designed to use excess solar watts (storage batteries at 100% and sun still shining) to heat water.

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On 10/1/2018 at 5:18 AM, noteven said:

There are electric water heater elements designed to use excess solar watts (storage batteries at 100% and sun still shining) to heat water.

Do you have a description of these, or a link to information?

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Be careful using a diversion element in a small water heater.  A BTU is defined as the energy needed to raise 1 lb of water 1 degree F, and there are 3.4 BTUs per watt.

If you divert 800 watts into the water heater, you'll put 2700 BTUs an hour into the tank.  This will raise the temperature of 6 gallons of water 60 degrees per hour.  If you start with 60 degree cold water, in an hour it will reach 120 degrees, in two hours a scalding 180 degrees and in 2 1/2 hours it will reach 210 degrees and trip the overtemp/overpressure relief valve.

 

Edited by Lou Schneider

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10 hours ago, DesertMiner said:

Some info here.....

Thanks.  It looks like it replaces the original heating element in the water heater.  If that's the case, does it mean you can't use it on shore power or generator any more?  Or, maybe you could, but you'd be having the charger working extra hard to keep up with the water heater?

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For other big solar readers, you can get away with smaller and easier wiring and no combiner boxes if you  wire in series. And that requires a controller capable of handling the input voltage. Yes, shadows can be a bigger problem, but not that big if  you park in the sun - where you should be anyway!

Edited by hemsteadc

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Check the wattage of your electric water heater, might be able to wire it through the inverter [will probably need a 2000 watt inverter]. If you are producing 1000 watts and your heater is 1450 watts, your battery will only have to supply 450 watts. You will have to monitor your panel input, and battery voltage, so you don't drag your batteries down too low. Agree with running panels in series , I am running 120 volts to charge controllers with only 10 gauge wire.. But try to park in direct sun with no shading. 

Edited by jcussen

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Part of the design process for my solar installation  was weighing the pros and cons of parallel vs. serial wiring. With 5 panels, each of which delivering up to 37 V, some parallel wiring was inevitable, so a combiner box could not be avoided. In the end, I found the advantage of harvesting the sun light more efficiently under partly shaded conditions outweighed the additional cost of less than $50 for the thicker wire, so all panels are wired parallel.

Edited by Loki
Typo

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1 hour ago, Loki said:

Part of the design process for my solar installation  was weighing the pros and cons of parallel vs. serial wiring. With 5 panels, each of which delivering up to 37 V, some parallel wiring was inevitable, so a combiner box could not be avoided. In the end, I found the advantage of harvesting the sun light more efficiently under partly shaded conditions outweighed the additional cost of less than $50 for the thicker wire, so all panels are wired parallel.

The only advantage to series wiring is reducing the gauge of the wire going from the panels to the controller.  The big disadvantage to series wiring is unless the panels have bypass diodes,  shading on any panel will reduce not only the current contributed by that panel, but of the entire string.

Edited by Lou Schneider

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All modern solar panels have built in bypass diodes. I have one array of three 330 watt panels, 40 volts each in series. When one panel is shaded, the other 2 panels still produce full current. House grid-tie systems, run about 600 volts with often 10 or more panels in series. Most commercial  solar farms run 25 to 30,  72 cell, 47 volt panels in series at up to 1500 volts.

https://www.civicsolar.com/support/installer/questions/what-bypass-diode

Edited by jcussen

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9 hours ago, Lou Schneider said:

The only advantage to series wiring is reducing the gauge of the wire going from the panels to the controller.  The big disadvantage to series wiring is unless the panels have bypass diodes,  shading on any panel will reduce not only the current contributed by that panel, but of the entire string.

Another advantage of series wiring is that you dont need a combiner box.

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I've been living full-time in my Arctic Fox 27 – 5L for almost 4 years and I live totally on solar. I have six Kyocera 140 W panels totaling 840 W. My battery bank consists of 4, 100 amp battle born lithium iron batteries. And just like you I built the system myself.

 I didn't build my system to run the air conditioner or any other thing that has a heating element in it, but it does run my microwave just fine. Being a full timer that boondocks about 95% of the time. I don't need air-conditioning, if it gets too hot I go somewhere else. I run my hot water heater on propane but only when I need it so it uses very little. I don't need a toaster, I seem to live okay without toast. And I don't have enough hair to worry about a hairdryer.

So what that all means is I have more than enough electricity to live a comfortable life, and in the four years I've lived like this only twice have I been in a situation where I had to go four days without any charging because of the weather. By the third day I had to start conserving a little but I made it through just fine. By the way I don't own a generator.

If you would like to read about boondocking in a 27 – 5L and living on sunshine you are welcome to visit my blog at    http://www.theboondork.com/mainphp there's a lot of useless drivel there but you might get a snapshot of what it's like to live on sunshine in an Arctic Fox 27 – 5L full-time.

Tom

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Outside the Northwood forum, you don't meet many people owning an Arctic Fox. I drove across the country last year from South Carolina to pick up my 27-5L, and didn't regret it for one second. I am RVing since over 20 years, and this one is the best brand I came across so far. Interesting to know that someone is fulltiming in an RV as small as the 27-5L. Usually fulltimers use the big Mobile Suites or the likes of them. I once lived with my family for a year in a 36 ft Montana 5th wheel, but, boy, was this a tin can compared with the Arctic Fox. By the way, the one time I enjoy the AC-running power plant in my RV the most is after hours of driving in the sunshine, when I get into the RV and it's not 95, but just 78 degrees. For me, it's worth the expense, and designing and building it was a lot of fun additionally.

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i have recently stated researching solar power. All I want to do is run 4.4 cubic ft residential fridge for 10-12 hours a day. I talk to people on line about it. They start using words I don't understand. I get confused, they get irritated, then everyone stops talking to me. I have a 1500 watt inverter hooked into the 4 truck batteries. I just need to know what solar panel to get to help the batteries. I have to run the generator when its hot to keep the wife happy with her air conditioner. So I can recharge the batteries at that time with a battery charger. I'm only doing this maybe 6 days a year. I'm not full time boondocking.

I might just forget about the whole thing and buy more ice.

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Here’s what I use to supply a charging voltage to my 4 batteries when in storage. It also works when running my small 4.0  fridge in the truck. If you buy the “blue tooth” version it lets you change setting and view the operation of the controller from your smart phone  I really enjoy this feature.

https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-75-10-75-15-100-15-100-20

I use a 100 watt panel I bought years ago...and I just set it out where it gets the best sun. If one panel isn’t enough then you can add a second.  

https://www.hqsolarpower.com/100W-12V-Monocrystalline-Solar-Panel-p/hqst-100d.htm

Panels are going down in price. Amazon has some good prices with free shipping. 

This is a nice “starter” set to get you into the solar world and you can expand from there if need be. 

Edited by DesertMiner

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7 hours ago, jenandjon said:

i have recently stated researching solar power. All I want to do is run 4.4 cubic ft residential fridge for 10-12 hours a day. I talk to people on line about it. They start using words I don't understand. I get confused, they get irritated, then everyone stops talking to me. I have a 1500 watt inverter hooked into the 4 truck batteries. I just need to know what solar panel to get to help the batteries. I have to run the generator when its hot to keep the wife happy with her air conditioner. So I can recharge the batteries at that time with a battery charger. I'm only doing this maybe 6 days a year. I'm not full time boondocking.

I might just forget about the whole thing and buy more ice.

Your question is not answerable without knowing or assuming a lot of parameters or variables. Let me try to give you an example that may or may not be helpful in your specific case: Assuming that your fridge has a wattage rating of 250 W (you can correct that according to your fridge's actual rating) and runs 50% of the time (depending how good the insulation is and the temperature setting), then the energy consumption in your 12 hours of usage is 1.5 KWh. That's the energy your solar panel must produce in one day, plus the electric inefficiencies between the panel and the battery and between the battery and the fridge, so I would say at least 2 KWh from your panel. So, how big a panel do you need for that? A panel rated at 200 Watt, for instance, delivers these 200 Watts only under perfect conditions, like full sunshine, no clouds, and sunshine from almost perfectly overhead. In my experience, you don't get more that 60% of the rated wattage on average during the 6 hours of most intense sunlight between, say, 9 am and 3 pm. Meaning, you harvest maybe 0.7 - 0.8 KWh of electrical energy a day even under clear skies with that 200 W panel. So, bottom line is, you would need 2 of the large 350 W panels that I used in my installation, or three somewhat smaller panels to run your fridge without draining your battery. Personally, I wouldn't consider investing the kind of money needed for the panels and the solar charger and the installation for 6 days a year!

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Yea you can buy a lot of ice for that kind of money. My goal is to eventually be all solar. Granted this is a long term goal. My youngest boy is 5. When he is off to collage and its just the wife and I, I want to be able to go anywhere and do anything without worrying about a generator. I figure I need to start playing with it now so I know in the future exactly what will work for us. I thought I would start small with just the fridge. I have a limited budget right now. Maybe I need to start smaller yet. Just run my lights and radio off solar. Then work my way up.

Thanks both of you for your help. Desert Miner I think I am going to order that set and experiment with it. I'm more of a hands on visual learner.

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👍 if I can help just let me know. I have a larger lithium based solar system on my trailer that’s still growing! Lots of the folks at the WCR will also love to show off their solar systems

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The Renogy 100 Watt 12 Volt Monocrystalline Foldable Portable Solar Suitcase with Voyager Waterproof Charge Controller is popular with van dwellers for its ease of use. You can buy it on Amazon with prime delivery.

Linda

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