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Efficiency of flat fixed solar vs adjustable portable?

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#41 Bosque Bill

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Posted 14 April 2017 - 06:11 PM

An idea from the RV world many RVers use a filled 1 gal. water jug to hold down their satellite dish, so not much weight to carry, but wastes a gallon of water that for boondocking will not work. 

 

A good idea. I carry a few gallon jugs with drinking water to supplement the water in the camper's tank, so that would easily work for early part of trip. I suppose grey water would work for later parts of the trip as I drain that into a gallon jug, too. Thanks for the tip.

 

My "portable" is not really a portable, but a panel wired to the house charge controller. I bought a controller that I could expand up to 400w, which makes adding a roof panel feasible (plus the fact that I had FWC add wiring and a roof plug when I bought the camper.)

 

p.s., still looking for recommendations for air gap between roof and panel frame, if you'd care to share your ideas.


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#42 JaSAn

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Posted 14 April 2017 - 07:23 PM

 . . .

p.s., still looking for recommendations for air gap between roof and panel frame, if you'd care to share your ideas.

 

The leading edge of my front panel is 1 inch above roof, the back edge is 2 inches (something I wouldn't do again).  I see no increase in temperature on the ceiling under the panels at 90ºF in full sun, measured with an IR gun.  Tilt probably helps a little with heat escaping.

 

The front panel is 10 inches behind the leading edge of the camper.  I get no bugs on the front edge of the panels while the front of the camper gets quite a collection; leading me to believe that the windshield/front of camper pushes the air stream over the top of the panels.  It's not affecting my gas milage any.

 

jim


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#43 Bosque Bill

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Posted 14 April 2017 - 08:04 PM

The front panel is 10 inches behind the leading edge of the camper.  I get no bugs on the front edge of the panels while the front of the camper gets quite a collection; leading me to believe that the windshield/front of camper pushes the air stream over the top of the panels. 

 

A very useful observation. I hadn't considered that deflection aspect. OK, I'll give myself a bit larger air gap to insure cooling of the underside of the solar panel and not worry so much about drag. Thanks, Jim!


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#44 RockCod

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Posted 15 April 2017 - 03:48 AM

Squatch and Bosque Bill,
 
An idea from the RV world many RVers use a filled 1 gal. water jug to hold down their satellite dish, so not much weight to carry, but wastes a gallon of water that for boondocking will not work. Tent stakes makes more sense but a PITA every time you move the portable.
I guess it beats shattered glass.
 
Rockcod,
 
I also use my portable in my Class C motorhome that does not have permenant solar so I will be keeping the solar controller on the portable even though I have a Zamp Solar controller for the fixed panel on my WTW rig. I like the flexibility of leaving the controller on the portable even though you can wire directly to the fixed controller.
 
 
UPDATE: Because I could not find a 160w flexible panel for a reasonable price I have opted to go with a popular 120w Cynergy panel from Solar Blvd. at $139. If this proves to be to small I'll be able to add a second panel, have 240w on the roof and still cost less.


Thanks for the info, I'll start with 250 watts on top and two batteries, it's wired for a portable so I can grow if needed, I'll be spending time in foggy skys, curious how it will charge. A flex panel @ 120 w would be a pretty lightweight addition if needed.
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#45 Bosque Bill

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Posted 15 April 2017 - 01:52 PM

Thanks for the info, I'll start with 250 watts on top and two batteries, it's wired for a portable so I can grow if needed, I'll be spending time in foggy skys, curious how it will charge. A flex panel @ 120 w would be a pretty lightweight addition if needed.

 

I was amazed at how much my polysilicon panel's output dropped with even fairly light high clouds. Other technologies may differ.


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#46 Squatch

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Posted 15 April 2017 - 02:22 PM

Not sure this is the right time/place to ask, but are most running the portable panel through, the house controller or an independent controller supplied with the portable .?

Thanks

I have a roof panel and a connector at the rear of the camper for the portable. I made my own suitcase portable. Both panels go through the Bogart SC2030 controller I installed in the camper. The roof and the rear connector for the portable are wired in parallel and go through a 30 amp breaker prior to the charge controller.

 

00620Small_zpshcfvc2yg.jpg

 

00720Small_zps3toonxzg.jpg

 

Thanks for the thoughts on weighting the panel. Reality is I probably won't carry the portable much. the 160 on the roof has had no issues keeping the battery charged.


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#47 RockCod

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Posted 16 April 2017 - 02:59 AM

I was amazed at how much my polysilicon panel's output dropped with even fairly light high clouds. Other technologies may differ.


That is one concern, I was amazed when I saw how much the output dropped by partial shading.
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#48 RockCod

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Posted 16 April 2017 - 03:04 AM

I have a roof panel and a connector at the rear of the camper for the portable. I made my own suitcase portable. Both panels go through the Bogart SC2030 controller I installed in the camper. The roof and the rear connector for the portable are wired in parallel and go through a 30 amp breaker prior to the charge controller.
 
00620Small_zpshcfvc2yg.jpg
 
00720Small_zps3toonxzg.jpg
 
Thanks for the thoughts on weighting the panel. Reality is I probably won't carry the portable much. the 160 on the roof has had no issues
keeping the battery charged.




I will probably install an upgraded controller from the OEM version my camper comes with, and I sure like the reviews and posts here about the info the trimetric battery monitor provides. I'm one of the "loves to know what's going on gauge types " Less than two weeks out. :)
Thank you for the pictures and info

--Rock
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#49 Squatch

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Posted 16 April 2017 - 05:48 PM

Love the info the Trimetric provides. Even in Dummy mode it tells you what you need to know. Easy to watch the draw of fridge and furnace and such.


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#50 ETAV8R

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Posted 16 April 2017 - 06:19 PM

This link has a ton of info. I read most of the links a couple years ago. Handybob solar is also a great resource. He mentions that if you even cover up a small portion of a panel with shade it decreases output by something like 70%.

http://forum.expedit...Solar-Power-FAQ

 

 

Last month I was in Death Valley. Upon arrival at the campsite I heard a weird noise as I begain to empty the camper. Once I removed my 100w panel I saw what the noise was. The glass was broken. Somewhere along the journey to camp the panel frame had bent, thus fracturing the glass.

 

The next day I moved again to a different location. I unloaded the camp gear again and began to set up camp. I decided to move the camper for shade reasons and forgot the panel was in front of the truck. This time the panel damage was my fault. I checked at the CTEK and it was a little lower than peak. Temps were a bit high and I'm sure my 0.7w fridge was drawing much more. The 2nd night in camp I looked at the fridge display and it showed an error. I thought I checked everything and even changed the plug to the main truck plug. With no fridge I decided to hit the road the next morning. Once driving and having the alternator charging the system the fridge was working again. Had I only run the engine a little while I could have determined that my house battery wasn't being charged by the bent/broken solar panel.

 

I have another new 100w panel at home since my original calculations per the reading in the first link suggest to double what you think you will need. This was mentioned in this thread already. Two 100w panels are quite heavy and getting them in the camper is a PIA so I did a few trips with only one panel and it has worked well up to this past trip.

 

In camp I tend to move my panels during the day to chase the sun. It really isn't a big deal if you are able to orient your rig and don't have a lot of tree cover, i.e. desert. I've not had to deal with a lot of trees yet since most of my trips are to desert areas. After the last trip however I did start wondering about mounting a panel to the Yakima tracks up top. I'd like to have the ability to angle the panel too. If anyone has come up with a fairly inexpensive DIY it would be great to see how to do it.


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