Crazy solar idea?

[Patricia D.]

Just putting my solar panel idea out there for reactions. Is this a crazy idea?
I would like to put solar on my trailer but having spent one season patching holes and fixing the roof, I do not want to put new holes anywhere if there is another way. Nor do I want to have to climb up to set them up when I stop. I would also rather not use a suitcase style panel, since I do not have a lot of storage space and they are more subject to theft.
I am thinking of making a second rock guard to put on the rear window and attaching a flexible panel to that. I would then make a cover out of heavy vinyl fabric ( like spare tire cover) to cover the whole thing when traveling. This would be mainly to prevent vandalism.
At the campsite I would just have to remove the cover and be ready to go. I would hope to park with the rear of the trailer in the sun and have several different angles possible for the panel.
In fixing the interior framing, I have put additional bracing above the window for this type of thing or a possible awning.
Any feedback would be appreciated.

[ShelbyM]

That sounds like an interesting solution. However, if you'd rather have the panel on the roof, you could mount it with VHB tape.

[Patricia D.]

Thanks,
I did consider the tape but as much work as I have done on my roof, It is still not completely flat so a flexible panel would probably not work. I would still have to make some kind hole for the wiring. If I did it on the back, I could run the wiring up (covered in moulding) and slip it in under one of the rear lights, I think. I have not thought that far ahead.

[sokhapkin]

Originally Posted by Patricia D.

At the campsite I would just have to remove the cover and be ready to go.

There is no guarantee that you will be able to park on the campsite with the panel looking south...

[tractors1]

Originally Posted by sokhapkin

There is no guarantee that you will be able to park on the campsite with the panel looking south...

True, but if the panel were retained on the rock guard with loose-pin hinges on each side one could then tilt it left or right to catch some sun by pulling the hinge pins on one side and tilting it up...........

[gordon2]

Originally Posted by tractors1

True, but if the panel were retained on the rock guard with loose-pin hinges on each side one could then tilt it left or right to catch some sun by pulling the hinge pins on one side and tilting it up...........

Would it be easy to remove? If so, then its just as much subject to theft as a portable panel (which is actually not that much IMHO). I camp in the woods, so I'd stick with a portable panel on 10-15 feet of cable, with the controller inside the camper. That way you can chase the sun, secure the panel with lock and chain (if its close enough to something you can attach the chain to), and if it does get stolen, its just the panel and not the controller, which probably cost well under $150.

[Jim Bennett]

I will be putting 4 flexible 60W panels on my roof, and plan to use EternaBond tape. It would allow for some imperfections in the roof. There will be a hole where the wires go in, but that will be well sealed using a Go Power Cable Entry Plate.

[Patricia D.]

"Would it be easy to remove? If so, then its just as much subject to theft as a portable panel"
i was going to have the 'rock guard"hinged with marine hinges screwed to the trailer. not removable quickly.

[Patricia D.]

Thanks everyone. All good comments and suggestions. Lots to think about.
And Jim, thanks for the link for the Cable Entry Plate. I may use that if I do decide to go the roof route.

[Steve Outlaw]

Remember, panel efficiency goes down as the panel temperature goes up,

solar cells absorb heat and generate less voltage at high temperatures. Since volts push amps into the batteries I would not mount any panel directly to a surface with no air flow underneath.

[Mike Magee]

Originally Posted by tractors1

True, but if the panel were retained on the rock guard with loose-pin hinges on each side one could then tilt it left or right to catch some sun by pulling the hinge pins on one side and tilting it up...........

The way most solar panels work, if you have a shadow fall on even one of the solar cells the entire panel drastically slows or even stops its output. The cells are linked in series and they all have to be getting sun for the panel to function properly. Your mounting location should take this into account.

[Jim Bennett]

Originally Posted by Steve Outlaw

Remember, panel efficiency goes down as the panel temperature goes up,

solar cells absorb heat and generate less voltage at high temperatures. Since volts push amps into the batteries I would not mount any panel directly to a surface with no air flow underneath.

I researched the crap outta the flexible panels, reading back upon about 5 years of usage, and read up on all the concerns, past and present with how heat affects solar panels. I found TONS of material, some of it a bit contradictory, but most following more or less the same line of thinking.

For starters, I did want to make flexible work, mostly because I did not want a big ass panel (or two) visibly mounted on my small roof. With the center area being narrow, only about 39" across I looked for panels that would fit in the four areas I have, and found that 60W panels would work.

Solar panels are given their ratings at a temperature of 25°C. Heat does have an effect on their effectiveness, but in the more modern ones to less of a degree, and newer technologies will have almost no issue with heat. It seems to vary, but the maximum loss due to heating is around 10%

Flexible panels have come a long way, and the newest ones are way tougher and much less prone to cupping like older ones were. They are WAY tougher too, using a ETFE coating which adds surface strength and solar absorption.

I looked at the fact I would have 240W of fixed panel on the roof, so I could afford some loss of efficiency, especially since I carry an 80W portable too.

As far as any loss from heat, to date I rarely camp in places where it gets that hot anyway. By far our biggest battery draw is running a furnace. Also, with the flexible panels mounted directly to the trailer, the interior now becomes the area below the panels rather than having them mounted an 1" up like rigid ones, and allowing air underneath. I figured that the air inside will be at least as cool as the air under panels, though I won't get the benefit of airflow from wind.

I have all the components ready to do the install, we just need to come out of our deepfreeze weather here, so maybe in a couple weeks. Still trying to decide on running all four (six counting the two 40W in the portable) all in parallel, or running sets of two in series, and then the three sets in parallel. Kinda leaning to the latter.

Anyway, after these countless hours of educating myself I came to the conclusion that for the small potential for inefficiency, I would gladly trade that for an out of site system that is much more aerodynamic too. Time will tell.

[Jim Bennett]

Originally Posted by Patricia D.

"Would it be easy to remove? If so, then its just as much subject to theft as a portable panel"
i was going to have the 'rock guard"hinged with marine hinges screwed to the trailer. not removable quickly.

The one problem with mounting flexible solar panels, is that removal is extremely tough. Rigid panels would be easier to steal needing to undo 4 bolts is all.

That said, I just don't worry a lot about theft. People are mostly good. Karma will get those that aren't.

[Jim Bennett]

Originally Posted by Mike Magee

The way most solar panels work, if you have a shadow fall on even one of the solar cells the entire panel drastically slows or even stops its output. The cells are linked in series and they all have to be getting sun for the panel to function properly. Your mounting location should take this into account.

Another reason I went with multiple panels, and will not run them all in series so that hopefully a couple get good light, otherwise out comes my portable.

[gordon2]

Originally Posted by Jim Bennett

I researched the crap outta the flexible panels,..

It's evident that you did your homework so it will be good to see how it all works out for you in the coming months and years.

I also did a lot of research and decided to NOT do as you plan. My reasons are partly, but not solely, because of the past problems with flex panels so its not apples vs apples.

What I want to know is where did you source your flex panels. As I'm sure you know, Renogy recalled and pulled their flex panels from the market a few years ago because of a fire hazard. They have been promising a replacement ever since, but they have yet to deliver, presumably because they can't get the technolgy to work well enough. (They do now have a lightweight ETFE Laminated panel but it seems that it is only available in 5 or 10 watt USB charging versions).

I have a 50 watt flex panel from China that has been working OK as a portable. Its super light weight although I need to mount it to a frame to keep it from bending out at two opposite corners making it less efficient. I have been thinking about putting it on the roof, more as a full time battery maintainer than a primary source of power. I will still have the option to plug in a portable panel using a through-hull connector on the front of the camper.

One hold up is deciding whether to use an air gap. If I do, I would have less faith in the mounting (at 65 MPH into a 30 MPH headwind for example). On the other hand, if I don't have an air gap than aerodynamically it should be good and the mount (even VHB tape) secure*, but then I would wonder if it would overheat. I put it on the roof last summer, just setting it loose on top, and it shortly got too hot to touch. I fear that it would not hold up being a cheap Chinese model.
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* Every time I hear talk of mounting using tape I feel obliged to mention the apparent failure of the gel-coat, when VHB tape was used to mount a glass solar panel. Any mounting with tape that is not aerodynamic should be carefully considered.

[Jim Bennett]

Originally Posted by gordon2

It's evident that you did your homework so it will be good to see how it all works out for you in the coming months and years.

Time will be the only true test.

My research ended up taking me to Lensun panels. Though a fairly new way of building flexible solar panels, the reviews I did find were all promising. I was having a heck of a time with getting them to me here in Canada, as combined purchase and shipping was brutal.
Black flexible solar panel

In turning my searching to "ETFE flexible solar panels" I found a couple more that seemed to get good reviews. There are a couple built with the same technology. GreeSonic is one I found more readily available to buy in Canada and got good reviews, but they did not have one the size I wanted. I then found these onese on AliExpress. They seemed to have exactly the same specs as the Lensun, offering a really good price, MUCH cheaper shipping, and next to no cost at the door for import and taxes as they declared the value ot be artificially low. I took a chance and ordered them. It took them not much more than a week to get here from Hong Kong. They look fantastic, and tough as nails, so I am initially impressed. Long 1.5m leads on them too, though they might have to be cut down to do a neat instll.
https://www.aliexpress.com/item/60Wa...608.0.0.Ijjwlq

That failure you linked to with bonding to fibreglass is something to be wary off, for sure. You are actually relying on the gelcoat holding. I will either be using the EternaBond 2" tape around the entire edge, or Dicor Lap Sealant again around the entire edge. Not worried at all about that letting go.

[gordon2]

Originally Posted by Jim Bennett

.... I took a chance and ordered them. It took them not much more than a week to get here from Hong Kong. They look fantastic, and tough as nails, so I am initially impressed. Long 1.5m leads on them too, though they might have to be cut down to do a neat instll.
https://www.aliexpress.com/item/60Wa...608.0.0.Ijjwlq...

First thing I noticed at that link:

Sorry, this item is no longer available!

Although they do have other options.. this one looks a lot like the one I got (from either Amazon or eBay, I forget).

https://www.aliexpress.com/item/Sola...684665815.html

[Jim Bennett]

Originally Posted by gordon2

First thing I notced at that link:

Sorry, this item is no longer available!

It is just that 60W size. When I ordered they said limited quantities left, and when I inquired if they still had four, they did. I musta bought them out.
https://www.aliexpress.com/store/gro...612.0.0.VvfdK9

[Patricia D.]

Thanks for all the information. Solar is such a quickly evolving area that it is hard to keep up. I appreciate all the input. Just to change the direction a bit (but feel free to continue with the panel discussion as well) . I am interested to know now what types of batteries you are using and what battery configuration would be good for a 100 w panel.

[stevebaz]

You could always mount the panels on top of a roof rack on your van and make your wiring lead with a 7 pin socket.

I personally use 2 smaller panels and put them on top of my Scamp through the emergency exit on top of the roof. I hang it by rope so I can either rest them on top or in the winter hang them off the side of the trailer. I try to keep it as simple as I can without over thinking it.