Three 280 watt solar panels on Casita 13 - Page 2 - Fiberglass RV



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Old 05-11-2019, 11:13 AM   #15
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Name: Brandon
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Will Prowse 24v system. LiFePo4 battery

Because of wind resistance, I’d mount the three panels on rails across the top flat, and prop them up when parked. You can park facing them south. They will shade each other in that configuration, in winter with acceptable losses. I will post a photo of my beamreach or you can look up the Beamreach videos to get an idea of spacing/shade.

If you build a big sail on your casita, you will need a massive amount of ballast to prevent it tipping over in the wind. During hurricane season, I’d remove all panels. The config I mention uses the tow vehicle as ballast, when hitched.

24v is a smart way to go. Very safe and batteries prefer to be in series. I built a system similar to Prowse’s like his suggested Giandel pure sine wave inverter so far. I oversized the solar (5kw) and charge controller (100a) to charge a future electric car. I have also been experimenting with ferrophosphate storage and would recommend them. It’s a noncombustable battery technology with potential to last a human lifespan, eg 14k cycles if treated right.



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Old 05-11-2019, 11:36 AM   #16
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My Beamreach

These three fully detached Beamreach panels survived significant wind gusting without moving. I neglected to use ballast or adhesive and have been pleasantly surprised that their wind profile is as good as it is. They are just sitting there without attachment. Each panel is 290w/p Or more . My friend and colleague designed Beamreach and I ask him wind questions.

One key is low tilt and full shrouds on the short long side between rows. This cargo trailer also has a continuous surface underneath them that prevents uplift in those areas.
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Old 05-11-2019, 12:07 PM   #17
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Wind profile

The beauty of an egg shaped camper is the wind profile, to increase fuel economy and towing ease. So Iíd not mess with that benefit when installing solar. Lightweight solar panels are monocrystalline sunpower cells in a thin, plastic, teflon-coated encapsulant. Glass panels get heavy and are not flexible. Lightweight flexible panels could be adhered direct to the shell, all over, with optimizers for each panel to account for mismatched sun exposure

Beamreach panels use thinner glass and a plastic frame, for example. There is a structural bar across the back and carry handle.

For a large, deployable array facing the sun, and maximum solar yield, I would still use lightweight panels. But the wind profile gets tricky, and the strength of the structure against wind an issue, as is tracking the sun. There seems to be a good solution to this, but it is probably outside the scope of this build.
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Old 05-11-2019, 09:13 PM   #18
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Two things come to mind:1) Those three PV panels will provide lots of shade, which will nicely reduce your need for AC, and 2) Lithium ion batteries from a wrecked hybrid or electric car could save you a lot of weight and size, with the extra benefit being that you can discharge them way further down than lead acid, without shortening their lifespan.
Back to point one - it has been calculated that it is 3-5 times less more expensive to generate electricity than to conserve it i.e. it may be money well spent to find a way to very well insulate the camper, to prevent the heat getting in.
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Old 05-13-2019, 03:38 PM   #19
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Originally Posted by Defenestrator View Post
Why 280W? If you're going all-out, it might be worth seeing if you can fit 3 of the high-efficiency LG NEON2 340W panels up there for only a tiny bit more space.
The main reason being that I got these three mono panels for under $300. They were set to go on someone's roof and I guess they couldn't fit them into the grid or something along those lines ( this was 3+ years ago). They are nice panels made in Canada, and from when I tested them, they are putting out more power then what is stated on the label.

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Originally Posted by bmoores View Post
Because of wind resistance, I’d mount the three panels on rails across the top flat, and prop them up when parked...

If you build a big sail on your casita, you will need a massive amount of ballast to prevent it tipping over in the wind...

...I have also been experimenting with ferrophosphate storage and would recommend them. It’s a noncombustable battery technology with potential to last a human lifespan, eg 14k cycles if treated right.
I think you may misunderstand how I am mounting these to the roof. All of the panels will stack on top of each other like a stack on pancakes. They will be on 42" drawer slides that slide the two bottom panels out to the sides, almost like two mini awnings on the long sides of the camper. The total height of the rack is about 6 inches. It will also be wrapped with an aluminum skin paneling that will make it more areo-dynamic, and make it more "like one" with the camper from a towing point of view.


I didn't go for the slim or "glue on" panels because I think they look absolutely horrible, I hear they have poor performance over time and also because the large panels will provide shade to cool the camper.

I saw the video on the ferrophosphate batteries and my only problem would be the temperature boundaries for the batteries. They seem to be pretty sensitive to temps. In the summer, I could see the batteries getting way to hot sitting in the sun or being enclosed in a box in the sun. which would drastically affect the performance of the batteries over time. I know this is with almost all batteries, but lead acid are relatively cheap to replace.


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Two things come to mind:1) Those three PV panels will provide lots of shade, which will nicely reduce your need for AC, and 2) Lithium ion batteries from a wrecked hybrid or electric car could save you a lot of weight and size, with the extra benefit being that you can discharge them way further down than lead acid, without shortening their lifespan.
Back to point one - it has been calculated that it is 3-5 times less more expensive to generate electricity than to conserve it i.e. it may be money well spent to find a way to very well insulate the camper, to prevent the heat getting in.
I looked at the 24v LiOn tesla batteries, but after a little research, I am too worried about keeping them safe. I just don't have the knowledge or experience to do it safely. Also, a used 250WH Tesla battery is about $1500, which is more than I feel like spending at the moment.

One of the main benefits of using these large panels is the shade they create for the camper. Because of the large air gap between the camper and the panels, it should essentially be like parking in the shade wherever you go. If you look closely in the pic, you can see that I also used 3/4" polyethelyen foam that has a pretty good r-value. Its also an amazing sound insulator that is closed cell and highly water and chemical resistant.


I just go the drawer slides in so I will start mocking up the panels and figuring out how I am going to do the wiring so that the panels can move in and out without pinching wires or hanging up. I will post more pics as I go. Just had a busy week and weekend due to going out of town for a wedding.
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Old 05-13-2019, 05:20 PM   #20
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We are arranging to have solar, wind, and hydroelectricity generated wherever we go before we get there, and wired in ready for us to use. We find 110/120V acceptable and will accept no substitutes except for our 12V car battery running our 12V/110V car ice chest and our trailer lights...


Hence, yes, shore power.


I know, I know.


I know.


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Old 05-14-2019, 01:16 PM   #21
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Originally Posted by Kai in Seattle View Post
We are arranging to have solar, wind, and hydroelectricity generated wherever we go before we get there, and wired in ready for us to use. We find 110/120V acceptable and will accept no substitutes except for our 12V car battery running our 12V/110V car ice chest and our trailer lights...


Hence, yes, shore power.


I know, I know.


I know.


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LOL. I have no problem with that! Different strokes for different folks.
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Old 05-14-2019, 05:00 PM   #22
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LOL, thanks Bill. YMMV! Your Mileage May Vary.

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Old 05-15-2019, 07:25 AM   #23
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So I have been doing dome more research on batteries and I think I'm going to change my plans a little.

As bmoores mentioned, LiFePo4 batteries have a ton of advantages. What I didn't know before is that they can be stored inside of the camper because they are completely sealed and don't off gas anything, and they are safe enough that I don't have to worry about them catching on fire. If I put them inside of the camper, I'm pretty sure I can find a way to keep them below the 140F Max temps.

The LifePo4 batteries will also give me more capacity, in a smaller and lighter footprint. The batteries I specd will weigh 92lbs (vs 320+ lbs for 4 Trojan 1275's) and give me 24v 240AH. That's 200AH of useable power @ 24V, which is a good amount of power. The footprint should be roughly H7" x W11" x L16"

Something else I found out while researching these batteries that I don't see many other people talking about is how efficiently they take a charge compared to a lead acid battery. Lead acid batteries have a pretty high resistance, which means a good portion of the energy (almost half) going from the solar panels and into the battery gets turned into heat, instead of stored energy. LifePo4 batteries are about 96% efficient. Because I'm trying to pull as much energy as I can from the panels, it makes sense not to turn that energy into heat. They can also discharge higher power loads more efficiently.

The downside to these batteries is they aren't cheap and you generally have to assemble them yourself. However, if you factor in how much more efficient they are and how much longer they last, they are actually cheaper long term.
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Old 05-15-2019, 11:01 AM   #24
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...The batteries I specd will weigh 92lbs (vs 320+ lbs for 4 Trojan 1275's) and give me 24v 240AH....

so all your DC electrics on board will need to be 24V rather than 12V? water pump, fan, fridge, water heater control, lighting ?
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Old 05-15-2019, 02:06 PM   #25
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so all your DC electrics on board will need to be 24V rather than 12V? water pump, fan, fridge, water heater control, lighting ?
No, I will be using a 24v to 12v step down by Victron. It is capable of producing 25 amps of power at 12V. The only 12V items I have in the camper are the refrigerator, lights, and water pump and a few other small electronics with minimal draw. However, the 24V system allows me to cut down the amperage draw in half of what is needed to power the inverter at 12V.

https://shop.pkys.com/Victron-Energy...ut_p_1697.html
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Old 05-19-2019, 04:39 PM   #26
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So I got the chance to work on the solar rack this weekend. I had to weld in a few cross bars to give the slides something to mount to. After that, I brought it inside because it is getting so hot outside. This was pretty straight forward....

I also bought 16 3.2v 120ah LiFePo4 batteries this weekend. I am waiting for the balancer I ordered to get here and I will post again when I put the battery together.

This thing is wide!


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Old 05-19-2019, 04:42 PM   #27
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Wow that looks like a great setup... Iím enjoying following your build
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Old 05-19-2019, 05:16 PM   #28
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Beautiful!
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