Flexable solar panel UNDER rear seal

Kmikesell · 04-29-2022, 12:08 PM

OK brain trust!

I purchased a recommended solar system off of Amazon and it appears that the panel, if placed on the rear shell, would be overlapped by the front shell when closed by about 4".

A: Is there enough "give" in the shell seal to not put undue pressure on the solar panel?

B: Is the seal soft enough so as to not scratch the panel?

C: Could I lay a flexible panel transversely covering the center "seam" in the roof?

D: Should I forgo all the above and place it on the front shell and run a much longer wire lead to the batteries in the rear?

Thanks!
Kory

**Bill** · 04-29-2022, 12:23 PM

Kory -

Be a little careful here. A solar panel is made up of strings of series-connected solar cells. A common number of cells in a string is 36, though there are other arrangements.If even one cell in a string is shaded, the entire string drops out. That is an issue with small (single-string) panels. (I have a 5-watt panel keeping my boat battery topped off.)

Larger panels are often constructed as multiple strings, and the panel incorporates what are called bypass diodes so that if one string is out, the other strings continue to operate. In more expensive solar panels, diodes may bypass smaller groups of cells, rather than the entire string. In this case, output is reduced, but not all the way to zero.

If you have a shaded area on the panel, you will certainly lose the string that is in the shade. The question is how all the strings that make up the panel are physically laid out. If the layout is such that a cell in every string is shaded, you won't get any charge when the camper is folded - when you are on the road, for example, or the camper is closed in storage.

BTW, I have no knowledge of the particular panel you are describing, and you didn't name it, so I can't go further. But if the panel is in your hands, you might want to check this out before you proceed with mounting it.

Bill

Kmikesell · 04-29-2022, 12:35 PM

Thanks Bill!

I am aware of the "some shaded, all shaded" issue. I have another solar panel set up that does just that.

What I am more concerned with is the storage issue. Will I damage the panel by having the front shell cover a few inches of the panel when the TM is closed? Or would in be better to mount it on the front shell and run 10' more cabling!

**Bill** · 04-29-2022, 12:42 PM

Kory -

That was your original question, of course, and I did not (and cannot) address it. Others will chime in.

Bill

**rickst29** · 04-29-2022, 01:15 PM

Flex panels have a bad habit of dying for no reason at all, and such a panel is much more likely to "croak" if the front shell's seal is pressing on them and scratching them.

Why not the front shell?

You could lay a flex panel across the seam with careful taping. (NOT pressing sharply into the bends around the seam between street-side and curb-side.) I did that about 5 years ago (front shell seam), and that "centered" flex panel is still working well.

**ShrimpBurrito** · 04-29-2022, 03:03 PM

Though not flexible, I installed three 100-watt panels on the rear shell of my 2720SL. There is enough room to install them with the long way going front to back, so it’s certainly possible with some panels. Mine weren’t flexible though.

Dave

Wavery · 04-29-2022, 04:31 PM

Scratching the panels are not as much of a concern as stressing the panel from road vibration. These trailers don't have shock absorbers and it's quite a rough ride back there. There is a lot of flexing of the roof as one bounces down the road and that flexing will be transferred to the solar panel. The front roof will be constantly bouncing on top of the solar panel the whole ride.

As discussed previously, the panels are made up of tiny wires that both make up each cell and connect the cells to one another. When those tiny wires are under stress like that, they tend to separate and result in a failed panel.

I had bad luck with flexible solar panels on my yacht. I'm not a real fan of them for RV use. Even when mounted flat on the roof (without having the top roof bouncing on one), there is still a certain amount of flexing going on from road vibration. I may be wrong but I don't see flex panels lasting as long a framed panels under these conditions.

.

Kmikesell · 05-02-2022, 01:18 PM

Quote:

Originally Posted by rickst29

Flex panels have a bad habit of dying for no reason at all, and such a panel is much more likely to "croak" if the front shell's seal is pressing on them and scratching them.

Why not the front shell?

I thought about using the fron shell (more room). But isn't there a power loss with a longer run of cable? One 100 watts panel (if you're lucky, more like 70 watts laying down) with a 15' 20' of cable lose a lot over that run?

**Bill** · 05-02-2022, 03:30 PM

This issue is often over-hyped and misunderstood. It is a really important issue when you have really long runs of wire, real small wires, or a large current flowing. But that is not your situation.

Think of it this way - 100 watts of power at 14VDC is about 7 amps. Number 10 copper wire has a resistance about 1 ohm per thousand feet, so if you had 1000 feet of wire, you would lose about 50 watts. But in 20 feet of wire, you would lose less than a watt.

Check my numbers, folks, but I think you are OK on the front shell.

Bill

Kmikesell · 05-02-2022, 04:14 PM

Quote:

Originally Posted by Bill

This issue is often over-hyped and misunderstood. It is a really important issue when you have really long runs of wire, real small wires, or a large current flowing. But that is not your situation.

Think of it this way - 100 watts of power at 14VDC is about 7 amps. Number 10 copper wire has a resistance about 1 ohm per thousand feet, so if you had 1000 feet of wire, you would lose about 50 watts. But in 20 feet of wire, you would lose less than a watt.

Check my numbers, folks, but I think you are OK on the front shell.

Bill

Thanks Bill!

Kory