Roof mounted solar panels

Dalehelman

Those of you that have permanently mounted solar panels. How often do you find that your camp site restrictes the ability of your panels to perform to capacity?

DougH

Maybe twenty percent?  We've been camping near the Tetons with a portable panel thirty feet from our site in one tiny splash of sunlight, but that's rare.  In less populated areas there always seems the be a spot somewhere on the loop with a southern exposure.  We just put a new pair of panels on that seem to be above 15V practically from sunrise to sunset (they're getting better every year), and a couple days ago in the middle of complete overcast and a light rain I was still getting 25V.  Heading out on a longer trip in a couple weeks and I'll experiment parking under more trees to see how much incidental light is enough to at least provide a few amps of charging. 

Are you concerned about portable panel theft?

Dalehelman

I just wondering how practical it is to have panels permanently mounted.

jgram2

But @Dalehelman, I thought yours were mounted on your TV rack. And it looked like a great idea.

Dalehelman

jgram2 said:

But @Dalehelman, I thought yours were mounted on your TV rack. And it looked like a great idea. 

Dalehelman

Dalehelman said:

jgram2 said:

But @Dalehelman, I thought yours were mounted on your TV rack. And it looked like a great idea. 

Correct . I was curious how practical the roof panels are.

N7SHG_Ham

Not on a Tab, BUT I built and installed a 160W system on a cargo trailer in 2005. It has worked fine for 13 years and I notice even in overcast days I get output from the panels to the charge controller. There of course is a trade off in everything, portability, convenience, theft, maximum output, etc. The system I built is on a roof top tilt rack, BUT I rarely tilt it because that turned out to be not worth the gain for the effort. I like a roof mount for convenience, harder to steal, charging while traveling are my key reasons. I have camped out of my cargo trailer, BUT not primary use, nice to wake up and charging is already under way at day break.

DougH

Keeping the fridge going while motoring was my biggest reason for going permanent.  I don't think I've ever directly heard of portable panels going absent, but the Norcold uses 150+ watts, at least until it gets down to temperature.  We have a portable Dometic, but I'm too lazy to transfer food back and forth.

rfuss928

I think the fact that they are always active is a big advantage.  My batteries are kept at a very high state of charge much of the time.  I often see the solar controller maintaining 14.2 -14.4v and 1-2A charge even when on shore power.  Well above the 13.8v max I ever see from the WFCO.  I have seen the trailer charging the TV more than once.

The panels are never ideally positioned.  Heck, mine are on a curved surface!

I have been virtually free from battery concerns or any maintenance for ~7 years. 

I carry a 80w foldable portable panel because of that time at Bryce Canyon NP when I wished I had just a little more after 3 gray days.  Sort of a solar spare tire.

The permanent solar is one of the best modifications I've made.

Tabfortwo

We have both 160 watts mounted and 120 watt suitcase. 
  

DougH

@Tabfortwo : So what percentage of your camping sites required the suitcase?

Tabfortwo

About 40% I like to put the trailer in the shade so I use the suitcase most of the time. It has a 40 ' cord 

DougH

Makes sense.  My previous panels went to nothing in the shade.

Tabfortwo

With just the mounted panels in partial shade won't keep up with the fridge.

ChrisK

For those with roof mounted panels, do you just leave them on all the time? I have mine set up so I can turn them off when not using the trailer. 

Tabfortwo

We do

AldebaranJill

80% of camping have been fully charged by late afternoon and the 20% that are heavily treed still get enough during daytime to offset fridge, lp detector, pump, lights. MPPT controller has been key since it gets me an extra 40% more current to battery. 

IslandJo

I have 2 100w rooftop panels. I started out with just one which is plenty in full sun. The East Meets West gathering this year made me realize I needed one on front & another on the back since my original front panel was under a tree but my back wasn't. A shaded 100w panel had a hard time keeping up with the refrigerator. 

BrianZ

I am still learning about solar a bit at a time, but wondering if it would be possible to roof- mount a solar panel (on either RV or TV), and still be able to take it down and connect it a 30 or 40' cable to set on the ground if RV is in the shade.  Are there any technical challenges/reasons why this can't/shouldn't be done or that would need to be provided for?  Haven't yet come across any links to TV-mounted setup examples, but we do have a roof luggage rack that we almost never use.

pthomas745

Two searches here:  one for "solar on roof" which shows different things people have done with their panels.  The second is for "solar mounted on truck roof" which shows a few mounted on roof racks, etc.

I've hung my light flexible panel on my Outback rack.  I've also suspended it from the Keder rail a couple of times. 

https://www.google.com/search?ei=t62SW87ZHYGasQWFtImgDw&q=solar+mounted+on+roof+site:tab-rv.vanillaforums.com&oq=solar+mounted+on+roof+site:tab-rv.vanillaforums.com&gs_l=psy-ab.3...2583.8585..9369...0.0..0.123.3224.36j1......0....1..gws-wiz.......0i71.y-uXfHl8Nco

https://www.google.com/search?ei=wa2SW4fCGcjktQWll6gw&q=solar+mounted+on+truck+roof+site:tab-rv.vanillaforums.com&oq=solar+mounted+on+truck+roof+site:tab-rv.vanillaforums.com&gs_l=psy-ab.3...23120.24197..25219...0.0..0.92.536.6......0....1..gws-wiz.PUMScC_r9l4

N7SHG_Ham

Fixed panels need a very solid mount to travel at highway speeds. I have two panels on a tilt up rack on roof of cargo trailer, solidly bolted to roof structural members, these things catch a lot of wind.

On back of teardrops they are a bit protected. Still in market for a 400, but I am thinking flexible panels mounted to roof permanently.

One thing to consider with remote setup is distance from charge controller/battery and size of wire, there will be some drop in voltage and heat generated if the wire is too small, especially if you start running 10a or so out of the panels.

BrianZ

Thanks, @pthomas745 and @N7SHG_Ham! 
So, what gauge wire would be optimal & practical for, say for example, a 30ft length between controller & a 150 watt panel that you'd like to be able to dismount from a TV roof and set on the ground?  

Tabfortwo

Buy one premade they come in a variety of lengths

pthomas745

@BrianZ you can drive yourself crazy chasing "voltage drop" and cable sizes.  I just ignore it, actually.  At these small distances, and my stock battery, it isn't going to make an appreciable difference.  As Tabfortwo points out, just buy a premade one.  I have these Windy Nation cables, and they are mostly 10 gauge.

The other reason for the 8 to 10 gauge is the thicker wires just simply will not fit into the (idiotic, poorly designed, frustrating to work with) connectors that are used in 99 percent of the solar controllers out there.  The more important distance is the space from the controller to the battery:  it should be as short as possible.

https://www.amazon.com/gp/product/B01L6OU4K4/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

If you want to dive into the weeds of solar wire size and voltage drop, get your calculator and read over this thread.  Lots of good info on several subjects, including voltage drop.

https://tab-rv.vanillacommunity.com/discussion/4608/voltage-drop-and-other-solar-musings-solar-lunchbox/p1

Normfun

Dale. I usually prefer to park in the shade so I went with overkill on the solar. I went with 6 50 watt flexible solar panels. I have two groups of  3 panels in series. This gives roughly 60 volts in open sun. With roughly 5 amps of current hence 300 watts. I find with mottled shade I get about 40 volts and 1 or 2 amps. When run through a mppt charge controller I see 3-4 amps to the battery. In complete overcast dark and rainy day I still manage .5 - 1 amp battery charge per hour.  I had 2 100 watt panels in parallel on my old trailer and it would not charge in the shade or rain.  Hope this helps some.  Solar is cool but finicky.