New ideas for solar panel installation

[Bill]

The forum is quiet these days, so maybe I can stir up some action with this.

When most of us think of adding solar panels to our camping rigs, we often think we must choose between mounting the panels on the roof of the trailer, or making them portable. This is a different approach. I think it has several nice features. Read on!

A month ago, my wife and I were settled into an ex-KOA in Van Horn, Texas, when the rig shown in the picture pulled in beside us. The truck, by the way, looks like a mini-truck in the photo, but was actually a full-size F-150 pickup with a cap over the bed. I immediately noticed the big wooden tray on the top of the truck, and the mysterious yellow wire leading to the trailer, so I had to talk to them about it. It turned out to be a solar panel array, of course, but in a mounting configuration that I had never seen.

They started off by telling us that they spend several months each year in Quartzsite, where they depend completely on solar power. But their small Casita trailer has no room for panels on the roof. Where to put the panels? Being mechanically capable, he built a shallow wooden box - a tray, really - that matches the size of the cap on the pickup. The tray rests on the cap’s roof rails, and is securely fastened to them. He removed most of the bottom of the tray, to cut weight and provide good air circulation below it. Then he built a second tray, just a bit smaller, that can drop inside the big tray. This second tray is built of aluminum angle stock, and it is also open on the bottom. The panels - 360 watts worth - are mounted to the inner tray. The cool thing - at least to my eye - is that the inner tray is secured to the outer tray using hinges with removable pins. By removing the appropriate pins, he can lift any one of the four sides of the inner tray up to a substantial angle (he said 30 degrees). This brings the panels up to the angle that best catches the sun. And since he can lift any of the four sides, he doesn’t have to point the truck in any particular direction.

The yellow cord runs from the solar panels to a set of four big golf-cart batteries on the A-frame of the Casita. The cord is short while they drive, so it doesn’t whip in the wind, and the batteries charge while on the road. In camp, the truck can be parked up to 50 feet away from the trailer, using an extension cord to bridge the gap. If they need to make a quick run into Quartzsite for groceries, for example, they can unplug the yellow cord, and take off in the truck with no worries about stolen panels.

With this approach, he has accomplished several things at the same time.
1. There is enough space for almost 400 watts of solar panels.
2. The panels are not shaded by the air conditioner, fans, etc. This maximizes solar capture.
3. The panels are easily tiltable in any direction, maximizing energy capture.
4. The system charges the batteries as they drive, something that portable panels can’t do.
5. The panels are out of sight and theft-proof - again, an advantage over portables.
6. He can easily disconnect and re-connect the panels when he wants to leave the campsite.
7. The panels themselves are protected from rocks and debris thrown up from the road. And by slipping a few blankets (or a sheet of foam board or plywood) into the outer tray, they are protected from hail.
8. The panels are securely mounted, without drilling holes in the roof of his rig.
9. The assembly does not increase the weight of the trailer (although the batteries certainly do!)
10. The cargo bed in the truck can still carry cargo. Since their Casita is small, this is important.
11. At the end of the camping season, he can lift the whole assembly off the cap, using a small hoist under the ceiling of his barn. No disassembly needed.

I like this. What do you all think?

Bill

[Larryjb]

I have two things I really like about the idea: 1) during winter storage the panels aren't exposed to the elements (tarped or not) and 2) it's not semi-permanently attached to the trailer making cleaning and raising shells easier. I may consider this when I delve into solar power.

[fairweatherfisherman]

Very interesting. Any guess as to how much that setup would weigh?

[klpauba]

That is awesome! Very clever.

[BrucePerens]

Panels with glass sandwich and aluminum frames weigh about 20 lbs per 100 watts. There is probably substantial weight added by the mounting scheme.

If you look at the cost of good panels, which is about $1/watt, it is in general better to add 20% more panels to a permanently flat system than it is to build a tilt mechanism. A 20% larger flat system would produce the same power for most of the day at continental U.S. latitudes compared to a system with one tilt angle set for the entire day. If you track the sun, you can beat the flat system close to sunrise and sunset, but at the cost of having the array raised to 90% at which time its wind load would be problematical.

The biggest problem is that panels handle shade poorly. Mine have three diode strings per panel, and if you happen to obscure a cell in all three strings, the panel stops conducting. I would like to have panels with a diode per cell rather than a string of cells per diode, that would probably work better.

[Bill]

As with most things, there are trades to be made. Bruce, as our resident skeptic, has pointed out a couple interesting ones involving the weight and cost of flat arrays vs tiltable arrays, and they need to be considered.

Trades:
At 20 pounds per 100 watts, if you add 20% more panels, you add 15 pounds of panels. Can you save 15 pounds by eliminating the inner (tiltable) tray and expanding the outer (fixed) tray? Maybe, but you won’t save much more than that. So this is pretty much an even trade.

At $1 per watt, if you add 20% more panels, you add $72 to the cost of the panels. Can you save $72 by eliminating the inner (tiltable) tray, and expanding the outer (fixed) tray? I doubt it, but you may come close.

In other words, from a weight and cost standpoint, flat vs tiltable it is pretty much an even trade for this configuration. But if your rig doesn’t have 20% extra area for additional panels, there is no trade to be made. The guy who built this thing made the trades that fit his needs and his rig, and others might make different choices. The point is that he has opened up some new ideas for all of us.

Bill

[Bill]

Any guess as to how much that setup would weigh?I wish I had asked the builder about weight - but I didn't. So here is how I would SWAG it.

Assume that the inner tray is 6 feet X 6 feet. That is 24 feet in circumference. If I build the inner tray using 1 x 1 x 1/8 aluminum right-angle stock, the aluminum angle weighs about 1/4 pound per linear foot, and 24 feet of angle stock weighs about 6 pounds.
Now double that number, to account for cross-braces, struts, nuts, bolts, etc. The finished inner tray is expected to weigh about 12 pounds.

Assume that the outer tray weighs about the same as the inner tray. Add maybe 5 pounds for the wood wrap. The total weight of the two trays is about 30 pounds.

Bruce tells us that the panels weigh about 20 pounds per 100 watts. The builder installed 360 watts of panels, so they weigh about 72 pounds.

Conclusion: Total weight for the entire thing is expected to be around 100 pounds.

Most of the weight is in the solar panels. They dominate the overall weight. The trays contribute relatively little.

You might choose to beef up the trays by increasing some of the pieces to 3/16" thick aluminum angle, or even 1 x 1 x 1/8 aluminum U-channel. They will be stronger, and the weight of the trays might increase from 25 pounds to 40 pounds. Quite reasonable.

Just my WAG, very loosey-goosey. Anyone want to suggest different numbers?

Bill

[Larryjb]

When I noticed the frame was made from wood, I immediately started thinking of different ways to build the frame.

3/4 PVC would be light, but perhaps too flexible. Perhaps filling PCV pipe with foam might suitably reduce the flex. I imagine you'd have to drill a number of holes and go through a few cans of low expanding foam for windows. However, if the frame is secured to the roof rack, this might provide enough support that additional structural support to reduce flex may be unnecessary. The PVC would be a nice conduit for wiring too. It would be easy to fabricate using T's and elbows.

An aluminum frame might work too. 1" square tubing similar to what's used on the TM might work fine. Unless you can weld aluminum, you might be faced with constantly re-securing the joints as they may come loose from vibrations. Also, metal so close to conducting electricity can be a recipe for shorts.

I'm sure there are lots of other concerns I haven't yet thought of. But hey, the got a man on the moon with a slide rule, I'm sure an lightweight solution can be found.

[Craigrrr]

I basically did the same, but with my suburban, I have 200 watts on the suburban and 1 panel on the TM, I can plug into the TM and parallel the panels for 300 watts total with a charge controller mounted in each the TM and the suburban. Seems to work great and I can run our Keurig coffee maker and induction cooktop as well using a 2000 watt pure sine wave inverter. I did this because our last trip to Missouri, we stopped every night and had to remove the bikes off the bike rack open up the TM hook up a generator etc... So I removed the second and third row seating in the suburban since it us only the two of us and dogs I made it into a sleeper aka Campurban, we can even just take the campurban out when we don't want to pull the tm and have a nice place to sleep. Even installed a 12 volt dc fridge in the campurban, so no more buying ice.

[klpauba]

Man, an induction cooktop? What kind of power does that pull?

[Craigrrr]

Man, an induction cooktop? What kind of power does that pull?

it is a single burner induction cooktop, 1500 watts , but the thing is, you don't use it for long it will boil water in under 2 min. just for an example of the speed it has to heat up and cook food. I do have a 200 AH battery bank

[Bill]

That's a really nice installation / conversion, Craig. My Dad, who was quite handy, would have been proud to do this to his Suburban. Of course, he had to cope with a wife and two young boys, a mid-size Airstream, and mid-1950's technology, so his challenge was a bit different. Nice work!

Bill

[Craigrrr]

Thanks Bill, the wife and I just got back from a 3 night camp with it on the Colorado river at the Cibola AZ BLM land . A real cool feature I liked a lot was the led motion sensor light I mounted on the side, when you want or need to get out in the middle of darkness the light comes on when the door opens and if someone comes creeping up on you, they are in for a surprise.

[rmschooner]

I am a new TM owner and have been enjoying the forum here. I am interested in the concept of adding flexible Renogy 160 watt flex panels w/ MPPT controller on top of my TM and to the Leer canopy of my F150. I could add batteries in the back of the pickup truck to gain some battery capacity beyond the two lead acid batteries on the tongue. We don't have factory air, so we will be adding some sort of A/c in the future. I have a Champion 3100 dual/fuel gen set that will also live in the pick up under the canopy. It will be vented for exhaust. Thoughts on wiring the two battery banks and panel arrays together? Two MPPT controllers?

[B_and_D]

Thanks Bill, the wife and I just got back from a 3 night camp with it on the Colorado river at the Cibola AZ BLM land . A real cool feature I liked a lot was the led motion sensor light I mounted on the side, when you want or need to get out in the middle of darkness the light comes on when the door opens and if someone comes creeping up on you, they are in for a surprise.

Would you please share the led sensor light that you bought?

I just installed a LED dimmable light in the front hatch and love it...

[rickst29]

I am a new TM owner and have been enjoying the forum here. I am interested in the concept of adding flexible Renogy 160 watt flex panels w/ MPPT controller on top of my TM and to the Leer canopy of my F150. I could add batteries in the back of the pickup truck to gain some battery capacity beyond the two lead acid batteries on the tongue. We don't have factory air, so we will be adding some sort of A/c in the future. I have a Champion 3100 dual/fuel gen set that will also live in the pick up under the canopy. It will be vented for exhaust. Thoughts on wiring the two battery banks and panel arrays together? Two MPPT controllers?
First, I don't think that any TM owners have installed more than 480W of panels (with the current record holder probably being lerderhos (https://www.trailmanorowners.com/forum/member.php?u=5303)). What power demands do you expect to have, requiring 160 more watts of "rated" panel power?

Second, I think that separating into two separate power banks (each 320W, with 2 batteries and a dedicated MPPT, and a pair of high current DURABLE cables between them, with a Circuit Breaker on the "+" cable) is sort of weird. If the Truck isn't under the sun frequently, the batteries need to be maintained by plugging into the TM.

As an alternative: Maybe put all of your panels on the TM, with a bigger MPPT - upgrading your batteries as required. You could convert a portion of a storage compartment into an SLA/AGM battery box (sealed and vented through the floor). Or for the case of a Lithium upgrade - merely a couple of clamps to to hold the battery(s) in place, plus some electric tape and wire clamps to keep other things from contacting current-carrying surfaces.

The correct MPPT controller for a 400-720 "Maximum Rated Solar Watts" is probably this one: https://www.ebay.com/itm/Epever-MPPT-Solar-Charge-Controller-12V-24V-Solar-Regulator-150V-40A-30A-20A-10A/351875294014 That's the 'Tracer4215BN 40A'. In this particular listing (which I have used), the BTS ins included (although I didn't use it , because I have Lithium batteries) .You must buy a BN model ("Battery Negative" Grounding), and absolutely not a different model (e.g., model "AN" with "Common Grounding" to "Battery +"). An Amazon seller has them all mixed up within a single product listing, don't go there.

This way, you need only one MPPT controller, and no weird interconnect wires.

[rmschooner]

Thank you for the response. The TM does not have an oven, it has the factory microwave with browning elements, which I am expecting is going to have quite the draw. We almost always look for shade when we camp. This is why the New Ideas for Solar Panel Installation intrigued me, the truck could be parked with panels in sun even if the TM is in the shade. I haven't sized the panels yet, 100 watt panels might easily do the trick. I won't know until I can get a better idea of power draw on the appliance side. My wife is an RV park kind of gal who enjoys shore power for all the niceties, I prefer the wide open spaces. Power is the limiting factor here, if I can provide the comforts of home the scales just might tip toward my favor.

Update: The Sharp Toaster Oven w/Microwave draws an insane amount of power... The microwave draws 980 watts the Grill/Bake 1300watts!

I can't imagine why the original buyer opted for this unit as an Upgrade. I might end up going for an outdoor camp kitchen with an outdoor propane stove and my coleman 2 burner, store in the truck. I have a propane tank in the back that runs my genset, I could Y off of that.

[rickst29]

Thank you for the response. The TM does not have an oven, it has the factory microwave with browning elements, which I am expecting is going to have quite the draw. We almost always look for shade when we camp. This is why the New Ideas for Solar Panel Installation intrigued me, the truck could be parked with panels in sun even if the TM is in the shade. I haven't sized the panels yet, 100 watt panels might easily do the trick. I won't know until I can get a better idea of power draw on the appliance side. My wife is an RV park kind of gal who enjoys shore power for all the niceties, I prefer the wide open spaces. Power is the limiting factor here, if I can provide the comforts of home the scales just might tip toward my favor.

Update: The Sharp Toaster Oven w/Microwave draws an insane amount of power... The microwave draws 980 watts the Grill/Bake 1300watts!

I can't imagine why the original buyer opted for this unit as an Upgrade. I might end up going for an outdoor camp kitchen with an outdoor propane stove and my coleman 2 burner, store in the truck. I have a propane tank in the back that runs my genset, I could Y off of that.
The 980W Microwave is 120VAC, and wants to be run from the Generator. It could be also run from a '1500 Watt Continuous' Inverter, but needs about 100A from a 12.8V Lithium battery to run. (That's how I run my microwave, but for only a few minutes per day.) Normal batteries can't be discharged as fast, and you would need a lot more of them.

My Microwave is a separate countertop 'el-cheapo' unit from some big-box store, my TM Stove / Cooktop unit is the standard propane. In the boondocks, it would make a lot of sense to displace the "Toaster Oven" function with a propane stove. When you don't have plugins, 12V battery power is too precious and 'expensive' to waste by making electric heat.

[rickst29]

We almost always look for shade when we camp. This is why the New Ideas for Solar Panel Installation intrigued me, the truck could be parked with panels in sun even if the TM is in the shade.
If I had to put two * 160W on the truck exclusively, for this reason - I could use a more "standard" connecting to a TM Solar Controller by wiring the panels in parellel. This is lower voltage (about 18V, the output of one panel), with double the current. Or, I could wire the panels in series - lower current (the current of one panel), but double the Voltage. The power is the same at the panels.

Higher Voltage is generally less safe in an accident. Lower Voltage is more safe, but looses more power by generating wasted heat within the long wires. (Resulting in "Voltage Drop" when the power finally reaches the MMPT through the wires.)

Putting batteries in the truck, with a charge controller, and connecting at 12.6-14.4V (Battery Voltage, under light discharge and maximum charging voltage) costs more, and has the highest "Voltage Drop" power loss. But it does avoid putting batteries elsewhere, within the TM.

[rbhtrail]

Hello All, We purchased our 2720qb and had a solar panel installed at the dealer on the roof. In addition I thought we would occasionally be camping in a shady area so I had an additional parallel port installed on the battery box to add a supplemental solar panel, so that I could arrange a second panel in direct sunlight.
Thanks for mentioning the winter storage, when covered an additional trickle charger may be necessary to keep the battery fresh. We're looking forward to our annual fall camping trip into the Catskills NY and enjoying the Peak color of the season in our new TM. Safe Traveling To All...

[Stephene1219]

With the great flexible panels out there, there really is no reason to use solid panel on an RV anymore. They weigh only a few pounds and are only about 1/4" thick. Renogy makes flexible panels up to 175W. I installed two of the 175w panels on the rear of the lower roof and connected then to the existing 100W panel and 30 AMP controller in less than an hour.

[Wavery]

With the great flexible panels out there, there really is no reason to use solid panel on an RV anymore. They weigh only a few pounds and are only about 1/4" thick. Renogy makes flexible panels up to 175W. I installed two of the 175w panels on the rear of the lower roof and connected then to the existing 100W panel and 30 AMP controller in less than an hour.If you connected 2, 175W panels to an existing 100W panel, the output of each 175W panel will be limited to the output of the 100W panel. You'd be far better off removing the 100W panel and allowing the 2, 175W panels to work their magic.

Having said all that, here are a few reasons to avoid flexible panels. 1, their lifespan is about 25% of the lifespan of "solid panels". 2. Flex panels laying flat on the roof get far hotter than solid panels properly mounted with 1.25" of air space for cooling. The hotter the panel gets, the less it produces. On a 80* day, a flat mounted panel might lose 20% of it's production compared to a similar solid panel.

[Shane826]

I’ll admit I usually skip over solar discussion but was bored so I took a peak. This is pretty brilliant, really.

Quick question… Why can’t a solar setup on the TM roof charge the batteries while going down the road?

[Wavery]

I’ll admit I usually skip over solar discussion but was bored so I took a peak. This is pretty brilliant, really.

Quick question… Why can’t a solar setup on the TM roof charge the batteries while going down the road?Who said that they can't?

[Shane826]

Bill did, kinda. I missed the PORTABLE panel part.

[Bill]

I did? I certainly didn't intend to say that. I can't find that reference, but maybe it doesn't matter. For the record, I'm pretty sure that ...

A SOLAR SETUP ON THE TM ROOF CAN CHARGE THE TM BATTERY WHILE DRIVING DOWN THE ROAD.

Bill

[Shane826]

Like I said, I missed the “portable” part of the statement.