Solar panel placement

[johnm1]

Hey all,

I'm researching solar for our new rig (Vengeance 25V)and I think my main concern is that we camp mostly in shaded areas and I'm wondering, can I mount 1 or 2 panels on the roof and have a remote panel on the ground that I can chase the sun with and have them all tied into the system at the same time?

We pretty much just want to use some LED lights, flush the toilet (which means run the water pump), the normal "phantom" draw (fridge, CO2 alarm, etc.) and MAYBE very rarely use the TV. So we're not looking for loads of power.

I know I have LOTS of other questions and issues but need to get the rig 1st and start really planning it out.

Thanks,
John

[mfMcFroggierPod]

Altestore.com


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[Bluepill]

PV panels that are even partially shadowed will drop their output drastically.

Link:http://www.pveducation.org/pvcdrom/modules/shading


It sounds like your best bet would be a portable panel kit that you could keep in the full sun.

LINK:

http://www.zampsolar.com/rv-solar-ki...ortable-solar/

[boondocking]

Yes you can set up your system with a couple panels on the roof and another portable on the ground. The best way to do it is connect them parallel, so you can use just two panels on the roof or connect up your portable panel to the system if needed.

Run the wires from the panels on the roof down the fridge chimmeny/vent and tie in a quick connect connection to the roof wires in behind the removable exterior fridge panel for your portable panel (easy access to connect portable panel).

The proper sized charge controller will operate just fine with 2 panels connected or all 3 connected.

[mud yapster]

[Klipstr]

I think you will probably find that having the panels on the roof will be enough and that fooling around with a moveable panel won't yield enough extra to make it worth the trouble. Maybe instead put four panels up top if you have the space. The panels, generally, are not the costliest item. The controllers and install are more. I've always done overkill on the panels and do a real good job of wiring. We have camped in sites where I was sure I wouldn't charge and came home to full batteries every time. That said, I always had at least 500W on the roof and generally more than that. See my blog referenced in the signature for more ideas about how to do this. Mud Yapster is my new hero. His rig looks very solid to me! He has so dang much real estate on his roof I'm thinking of leasing some from him!

There are decent selections of 12V solar panels on Amazon and some have free shipping if you are prime. Shipping will kill you as these things are bulky and odd shaped.

Mud Yapster's system could accommodate high voltage panels that are cheaper per watt as they are more widely used in the rooftop solar industry. They are physically larger so roof space on your rig has to be carefully mapped to ensure they will fit, but cheaper per watt. But you must have an MPPT controller like Mud Yapster has. The cost delta between the Morningstar Tristar MPPT controller and the same amperage PWM controller is $340. That $340 will buy you two more low voltage panels. Do yourself a favor and get one of the Tristars. They are better built and will provide better service to you than a cheaper one.

A long argument for our against MPPT vs. PWM will undoubtedly occur. And both sides of the argument will be technically correct but the difference in a small system will ultimately be trivial but the cost delta is not. Act accordingly. It boils down to a simple arithmetic equation. Sum the cost of the panels and charge controller and divide by watts. Maybe add a little fudge on the MPPT to make you feel better if you decide to go that direction or smile a bit at what you save if you decide to go PWM. You can't really go wrong either way. I've built both and loved both. On my big system I was smug with my MPPT. I had over 1000W on the roof and my batteries were always charged before 10:00AM. On my current rig I have 600W (4 LV panels) and the Bogart Engineering meter and charge controller. My batteries are always charged before noon. And I'm still smug!

I liked what Mud (I've shortened it) had to say about his top amperage output: he only saw that when his batteries were sufficiently discharged to need as many amps as he could get out of his system! I hardly ever see that and wish I did. Then you really know you have a great system.

Keep studying and then build yourself a killer system.

[johnm1]

This is some great info - thanks! Since we don't have the new rig yet I don't know what the roof looks like, which means I don't know what my limitations are for physical size, shape and location of the panels. I'm thinking that's the 1st thing I need to know?

With that said, is there any kind of a guesstimate on how much loss there is in a "dappled" sunlit campsite? Like I said, we camp mainly in NYS and there are LOTS of trees in NYS. Hence the question about trying to chase the sun with a remote panel vs permanent mounting on the roof. Obviously permanent is way easier since I wouldn't have to touch the system after install except for checking the battery water level.

I've also been pondering the age old question of (2) 12v (true) deep cycle batts in parallel or (2) 6v deep cycle batts (like the T-105's) in series. A friend may have just convinced me to look into going the (2) 6v batts and have a 12v "spare" on hand. Probably the one that comes with the rig. The 12v batt would be separated from the charging system via a battery switch and get charged from a trickle/maintenance charger only when plugged into the campground power pole.

Thanks again,
John

[boondocking]

I have camped quite often on the west side of Vancouver Island (2-3 weeks in one spot) with big cedar trees shading my campsite. My batterys (pair of 6v) were always charged by early afternoon with 200 watts of solar (roof mounted).
I'm not much of a power hog, so your experience may be different.

[KMP44]

Originally Posted by johnm1

With that said, is there any kind of a guesstimate on how much loss there is in a "dappled" sunlit campsite? Like I said, we camp mainly in NYS and there are LOTS of trees in NYS. Hence the question about trying to chase the sun with a remote panel vs permanent mounting on the roof. Obviously permanent is way easier since I wouldn't have to touch the system after install except for checking the battery water level.

We camp extensively in NYSP's - mostly in the Adirondacks. I bought two 100 watt panels intending to put one on the roof and keep one portable. After a couple trips last year playing around with the portable one, I didn't even bother mounting the second one on the roof. We are now revising our file of favorite sites at the different parks based on "solar friendliness" but camping in the woods is a challenge when trying to generate solar power.

We've found that some sites have an open area in the tree canopy that allows for solar, but frequently there is no way to get the trailer unto the right spot. Portable is the way to go. And the other big advantage to portable is that it is easy to angle the panels. You can easily get 30-40% more output by angling the panels. With 200 watts of panels, we were making 8-10 amps regularly in the spot pictured below. But, I had to move the panels 3 times over the course of the day to keep them in the sun. Just laying them flat in one spot (as they would be on the roof) would only produce 2-3 amps most of the time. Went 5 nights (including one rainy day) with no problem keeping the batteries charged.

Roof mounted is also good for a built in battery maintainer in storage. At the beach or other open areas, roof mounted for sure, but in the woods, I would stay with portable. The one major downside - the panels are fairly heavy & bulky so transporting and setting them up is a pain. But they are useless if you can't get them into the sun. You can always put 20-30 feet of cable on one and try out as a portable. See how it does and then decide if you want to mount it (or mount a couple additional ones).

But the short story is we have been happy keeping them portable and love dry camping without a generator.

[johnm1]

We do most of our camping in the Adirondacks as well and we're conservative with power usage too so maybe portable is the way to go.

[Klipstr]

(it should be noted that I wrote this before reading KMP44's response. I don't disagree of with any of his assertions including the bulkiness of moving and storing solar panels!)

Shade is definitely a problem with solar but you don't have to have direct sunlight to generate electricity. You will get some charging in the shade. I think having solar will direct your choice in campsites going forward! You will be looking for those nice bright sunny spots!

The problem with portable is you have to find a sunny place in that already shady spot and move the panels around. And how long does that spot stay in the sun. You don't want to spend the day moving a panel from place to place. And finally getting sufficient wire size to support proper voltage to the charge controller is an issue especially as the length goes up. Heavier wire, longer length harder to store, drag around, etc. We camp in shady spots too. The sun is directly overhead in all of them at least for a while. And in the summer maybe enough.

As for batteries: I have two Crown 6V. They are equivalent and perhaps better than the Trojan T-105 that I had in my previous rig. Both are great and that's the way I would go. I have not worried about having a spare as I've never had a problem with properly maintained batteries. I suppose if push really came to shove you could use your tow vehicle battery. There is an discussion about two twelves vs. two sixes elsewhere in this forum. Until somebody brought up battery failure in that thread I had not considered it and certainly have not worried about it. Having a third, spare, battery aboard would give you one more thing to worry about: is the spare charged? Is it being maintained properly? Might as well take care of the two. Again, I have never heard of a battery (especially a relatively new one) failing. Could happen I guess. Worst case go home!

Yes, roofprint is usually the place to start in the design: make sure you can put some more or less standard sized panels up there to begin with. Most rigs have stuff mostly down the centerline leaving space out on the edges. If you look at Mud's rig you can see what I mean. In my case I have my panels forward on the rig with the vent fan for the bed between and then for the other two panels the AC is between them. There will be some shading of the panels by the AC cowling but it won't last long and I have 600W up there which is probably 300W more than I actually need. Back to the oversize thing. Take a look at some possible panels and get rough dimensions: usually 20-30" wide by 45" or so long (width is more important than length generally). When you get your rig head up top (don't worry about walking on the roof) and measure everything. Since you've already scoped out the panels you will know where you can lay them on the roof. You can also see where you will be able to fish wire down to the charge controller and batteries. Lots of ways to do that. I have not seen too many roofs where I could not put the required number of panels. The 100W panels I looked at on Amazon are 22" x 45". Lots of places to put those on most all rigs. The 150W panel is 27" x 58". Remember you can safely mix and match (again, the arguments will rage and technically everything said will be accurate but none of it will matter in this scenario).

I'm a real practical guy. I want to see as many people as possible use solar. I don't want to listen to generators when I'm camping! Ever.

Take a look at my blog shown below (if you haven't) to see photos of several rigs and how the panels were laid out. It ain't rocket science!