Selecting a solar panel, brands, and requirements for RVs?

[Diesel Junkie]

Hey guys,
Im shopping for new solar panels.
I want large, efficient RV style roof top panels. Not small tent camping stuff.

I had 2 of these flexible panels, but lost one. They need a frame to be mounted to a hard roof. I want something better.
https://www.amazon.com/HQST-Monocry...+Volt+Monocrystalline+Lightweight+Solar+Panel

I am happy to pay for the high end stuff, mono-crystaline, and highest efficiency.

I am really sucking at researching this.

Questions:
Are there special considerations for the roof of an RV vs just a house panel?
I dont see a lot of special frames constructed for light weight, or added robustness for being on a vehicle.

Any suggestions on brands or RV specific panels?
Been trying to figure out what brand/model of panels the earth roamer uses. They always make the smartest choices.
Any advice is much appreciated.

 

[dlh62c]

YouTube should have answers to your questions. Plus product reviews. I prefer a portable set of panels so I can park in the shade.

 

[dwh]

This is a (very) rough illustration of how it's done:

Except the frame is usually more like:

The first illustration left out a semi-insulating layer between the silicon wafers, and the backing is usually a couple of layers of different rubbery stuff, but close enough to get the general idea.

Tempered glass, usually rated for high winds and hail. Glued into a sandwich with an aluminum frame for support - approximately as hard to break as a windshield. (And as easy to crack by flexing...)

Aluminum frame to reduce/prevent the flexing and provide a mounting point. Doesn't really get much lighter than that does it? Besides, it's the glass that weighs.

Nothing special for RV use except maybe a few extra mounting brackets to the aluminum frame.



The main difference between those above and the "semi-flexible" is no tempered glass or aluminim frame.

 

[dwh]

"Efficiency" isn't actually all that efficient.

The theoretical maximum light->electric conversion efficiency for silicon glass solar cells is around 30%. NASA often uses custom cells made of gallium aresenide instead of silicon because of that.

El Cheapo might get 13%-15%. Renogy sells poly- crystalline 17% or mono-crystalline 18%. Top of the line from Sharp or Panasonic can hit 22%.

It starts to add up and really matter when you are talking multi-thousand watt arrays. On an RV? Meh, too small to care about unless you're going all Cap'n Cuthbert and sticking a 2kw array on a Shachagra.

 

[AndrewP]

Home depot of all places had a recent good deal on an 18% efficiency 180 watt panel. It is nearly the exact same size as a 160 watt panel I bought last year. THe price seems to vary, I paid $199, then it was $258, now it seems to be $219. Decent panel though.

http://www.homedepot.com/p/Grape-So...ck-Up-Power-Systems-GS-STAR-180W-US/301024442

These are also good and cost effective panels, I have one of these on the roof of my Land Cruiser:

http://www.ebay.com/itm/1-160-Watt-...%3A40dbdf3215c0aa42c24eb837fffefa67%7Ciid%3A1


But you really need to decide how much solar you need. What loads do you want to run, and how big is your "house" battery bank? Where do you plan to use it? If it's clear and sunny most of the time, you can bet by with less solar.

 

[dwh]

Not sure what Earthroamer is using these days. Don't quote me on this, but I seem to recall they used to use the Kyocera 180w panels (high quality, 16%, poly):

https://www.wholesalesolar.com/1101...0-watt-with-mc-plug-in-connectors-solar-panel

 

[Diesel Junkie]

Thanks for the input guys.

My "system" is all designed and done.
I have been running it for a couple years now.
Prostar 30 charge controller.
Go power 3000watt pure sine inverter.
2x optima yellow top.
Blue sea 500 amp automatic charge relay.
all in an underbed box with a pretty good air compressor too. The puma.
100% of the electrical accessories I have added to the truck are on the RV battery side of the relay.
It keeps the ARB happy, and runs 16,000 lumens at night, and charges my phone.

My problem is I was running those 100watt mono crystaline flexible panels on top of the alucab rooftop tent.
I dont like the flexibility, and then I made some really crappy brackets in February in haste to get ready for a trip, then I finally lost one.

So I need to replace the panels. (Panels only.). If there was a super gucci one, that would be rad.
I guess any panel that fits my size will work.

Do the framed panels usually come with mounting holes? or can you just drill the frame where ever you want?
Do those Home depot ones come with the "standard" solar connectors on them?
The home depot ones in the store too?

 

[jonyjoe101]

I have always use house panels on my astrovan. First I had a kycora 120 watt panel (6 amps), then I upgraded to a larger sharp 240 watt mono panel ( I seen up to 15 amps when charging my lithium, about 12 amps with agm this is with panel being flat on roof and my 20 amp ecoworthy mppt). Pictures I've seen of large RV's all show house panels. Your only limited by the space on your roof.

In 4 years the 240 watt panel has stood up to being on my daily driver. They are well built, and there is enough room on the frames to drill holes for mounting. On the panel the actual solar module is very light/flexible, the frame itself only surrounds the module. Like on the picture below, the backing layer is very thin.

 

[dwh]

Note the weight difference between the Grape Solar 180w panel - 26 lbs., vs. the Kyocera 180w panel - 36 lbs.

The extra weight is glass and aluminum. Guess which one is stronger...



Here's a Panansonic high-efficiency. Note the cells are 22%, but the panel itself is 20%:

https://www.altestore.com/Solar-Electric-Panels/c541/

Again, it doesn't much matter until you get big enough.

 

[dwh]

Some come with pre-drilled mounting holes in the frame. Some don't. Used to be none did.

 

[AndrewP]

Note the weight difference between the Grape Solar 180w panel - 26 lbs., vs. the Kyocera 180w panel - 36 lbs.

The extra weight is glass and aluminum. Guess which one is stronger...

That's sort of a silly thing to say, and I would have expected better...


The extra weight of the Kyocera is glass and aluminum, but is also physically significantly bigger. Makes sense, it's a less efficient panel. Just saying the Home Depot Grape Solar is a decent mono panel, it isn't too expensive, and if anything goes wrong with it in the near future, it can easily be returned to home depot. There are many choices out there, most of them good, but I've have never heard of anyone with long term (like more than a year or two) success with flexible panels.

I look at anything you put on the top of a moving vehicle as sort of disposable. The idea that a 25 year warranty makes any difference at all, is laughable. I seem to upgrade every year or so!

It sounds like the OP, at best has about a 200 amp hour battery bank. That would call for right around a 200 watt panel, or 2 panels of 100 watts each. That should be easy.

The Renogy high efficiency panels would work well. It isn't clear, but it sounds like the OP has a PWM charge controller, so that kind of limits him to "12 volt" panels. House panels are cheaper per watt, but the higher voltage of house panels pretty much says you must run an MPPT controller.


edit: and let me say, I've had no issue with the panels on the roof. Just got back from a 1700 mile round trip to Arizona, no issues. Even got small hail one day with no issues. Went through the Rubicon trail last year with the panel on the roof, no issues, and plan the same this year. I wish those flex panels had a better reputation because the weight savings is nice. But I'm ok with a rigid panel on the roof, and in my experience at least they have worked very well in a variety of terrain/situations.

 

[Diesel Junkie]

Now that I have attention of some experts, I have a question i have worried about:
My starter batteries and house batteries connect automatically with the blue sea systems automatic charge relay. (Connect when voltage is high).
I used to only setup my PV array when camped. Now that its mounted, it runs all the time even when the truck is running and driving. So when the relay connects the starters and house batteries, and the engine is running, I effectively have 2 charging systems regulating voltage to a common (4 battery) bank at the same time. The alternator, AND the PV array/charge controller.
Is this sittuation bad?????????? or ok?
I would assume that each charge regulator has its own float voltage, and the "higher" one usually wins, with the other just sort of shutting off when it sees a quarter or half volt higher than it wants.
I have been running it like this for ~4k miles of driving since February with no issues.



I need a 12v panel. Pulse width modulated controller.

This is my charge controller:
MorningStar ProStar PS-30 PWM Solar Charge Controller, 30 Amp 12/24 Volts


I would kind of like to get a single panel this time around rather than 2x. I think it should look cleaner, and I dont like the bundle of wires and splitters I had up there.

I am putting the PV array on top of an Alucab tent. The rails are 44" center to center and 50" long, So I would prefer a panel that can span the rails to make bolting them down to the rails easy. but not a LOT wider than the rails. so like 46" min and maybe 50" max width by up to ~48" the other way. Does that make sense?



Thanks for the input.

 

[calicamper]

Get a LG panel 25yr warranty 310watt? They hover around 18% efficiency. I put 285's on my house. Nice stuff.

 

[Diesel Junkie]

I just got 2 of these:

18+% Renogy, newer smaller package. No wires on the face of the cells. All the interconnects are on the back.
If my calculations are right they will fit really well across the rails sideways.

https://www.amazon.com/gp/product/B01B3TEM1E/ref=ox_sc_mini_detail?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Thanks for the help!

 

[AndrewP]

Sounds like it will be nice. 200 watts sounds about right and will pair well with your controller. Those Renogy panels are spendy per watt, but the smaller size and lower weight have value.

No problems leaving both systems on all the time. I have a BlueSea ACR too and do that during the summer when I'm using the trucks more often. Since the ACR will combine them only when charging, it's fine to have different batteries, but your "bank" of house batteries need to be the same.

Get a LG panel 25yr warranty 310watt? They hover around 18% efficiency. I put 285's on my house. Nice stuff.

He said he had a PWM controller, so those nice LG panels would be wasted being forced to operate at 12 volts. If he had an MPPT controller and the space for a big panel, those would be nice panels to run.