Proposed Modular Roof-mount Solar Project

Next big project. I'm running this tome up the flag-pole to see what others may have to say about this before I go all-in.

Here's my wish list:

1) I wish to extend our boon-docking capabilities. We have a 2017 560, without the CI solar option, and with a Dometic. With our Dometic use (calculated at about 20 ah/day at 50F differential from ambient, per published specs), I have calculated our likely daily consumption to be in the area of 25ah/day. Given our 72 ah battery, and with conservative use of the other minimal electrical peripherals, such as pump, fan, phone charging and LED lighting, I figure we have about 2 1/2 to 3 days of boon-docking capacity. Which... is in the ball-park of what has been suggested elsewhere in the forum. A single 100W panel will be able to extend (possibly even double) this boon-docking time. I acknowledge there's a lot of personal use and environmental variables that can affect this equation. We don't have to live indefinitely on solar; 5 or 6 days is plenty.
2) More importantly, I wish to augment the TV's limited capability to fully charge the trailer battery while on the road. Cary quotes 85% as typical amongst most car alternators, though I have yet to really confirm this with our 2017 Outback TV-TD set-up. A more recent post about the new CI CTEK charger option (read here... Teardrop Travel Trailers by Camp-Inn) would tend to confirm that this problem of under-charging while on the road is only going to become more common and more significant with newer model TVs and their 'smart' alternators.
3) I want some flexibility in where I am able to position the panel(s) when camped, and to be able to angle them, to get the most charging bang for my buck, but not at the expense of diminished security of the panel(s).

Here's my Non-Wish List:

1) I don't want a portable panel that's bulky, heavy and hard to store (when not in use) and can't safely and easily secure (when in use), and which can't charge on the road.
2) Nor do I wish a standard framed panel mounted completely flat on / into the roof, with it's inherent drawbacks of potential water leakage, decreased (or non-) performance due to shade and sun angle, and the lack of flexibility of use.
3) I don't want to mount/glue a thin flexible panel to the trailer roof, owing to its potentially poor (i.e. flat orientation) performance, despite the significant benefit of it not putting holes in the roof of the trailer.
4) I don't want to add another battery anywhere. Or carry a Goal Zero, despite it's superficial bling appeal, and because of it's limited ah rating and charging options (Lithium). Having to charge a Goal Zero (flooded) via 12V, along with the trailer battery, and running the Dometic, is just too much of a demand on the alternator.
5) I don't want to be dependant upon electrical sites being available when and where we need them to fully top up a battery.

Considerations:

1) A permanently-mounted flat panel on the trailer roof will always perform well below its maximum output, if you can't angle it. And when the trailer must be parked (or is chosen to be parked) in a shaded location, this lowers or eliminates completely the panel's power output when at a camp site. The best part of the day to charge via solar is also the least likely time that you will be around the campsite to manage a panel, and (hopefully) you're doing other things away from it.

2) Although thin flexible solar panels have come a long way in the past few years, the lack of rear ventilation for a flush-mount has plagued many of the early designs with premature physical deterioration owing to overheating. These elevated temps also contribute to a decreased overall performance, electrically speaking, even if the panels don't break down, delaminate, cup and retain gunk that blocks sunlight reaching the cells. These issues have been recognized and addressed by some manufacturers recently, but not so long ago that they are able to boast of a definitively improved product and a new proven track record. We park our 560 in the garage, so extended exposure to the sun, if this degradation is still occurring with flush-mount panels, likely will not be a problem for us, even in the long term.

3) I have access to Sunware in Germany who make a (sadly) expensive but thin flex marine solar panel that doesn't overheat or deteriorate when installed as a flush-mount, and is designed to optimize power production in partial shade or as a flat-mount . Renogy Flexible (much cheaper) is my other option. Both panels are in the 2' X 4' range. No decisions yet.

I believe I have a solution that ticks all my boxes and mitigates many of the drawbacks of RV solar panel use and performance in general. Barring some other epiphany or revelation, I will be:

1) mounting a 24" X 48 " X 1" piece of HDPE plastic, forward of the roof vent, on the flat, using 3M 4952 VHB tape. The HDPE is inexpensive and relatively easy to come by from commercial plastic supply companies. Also used in the marine furniture business. It is waterproof and UV resistant, but it has a low surface energy (i.e. it's slippery and resistant to adhesives). However, the 4952 tape is engineered specifically for this type of plastic, and many other sources (i.e. Airstream forum) confirm that the 3M VHB line in general will hold solar panels well onto many varying surfaces. In the event that the plastic panel itself needs to be removed in the future, such as for installing a different size of solar panel, it can be done mechanically, with no damage to the aluminum, but it would take some effort. (possibly another forum topic, in the distant future).
2) On the underside of the 1" thick plastic I will countersink and glue four 3/8" stainless nuts; this leaves almost 3/4" of "meat" for the bolt to hold.
3) On top of the plastic I will place the thin (2mm-5mm) flexible 100W solar panel. It has mounting holes around the perimeter.
4) Holding the panel down will be a rectangular custom stainless frame, and 4 stainless bolts (1" or 1 1/4") with security heads that are tamper-resistant, but easily and quickly removable with the appropriate driver. Washers can be used ensure that the bolts don't extend beyond the embedded nuts and dent the trailer roof aluminum.
5) I'm contemplating adding pivoting legs to all sides of the frame to allow it and the solar panel to be propped up on the roof in any of the four directions/orientations, to optimize panel performance. This is a possible later add-on, after some practical use of the panel in the field, and a couple beers to assist me with the design process.
6) It will have a waterproof solar electrical quick-connect that will allow the solar panel and frame to be connected to a longer wire and placed a distance away from the trailer, in the sun, or to accommodate propping on the roof.

I haven't yet noodled a design that incorporates multiple roof panels, or that uses the curved section to the rear of the fan vent. Or a system with a single fixed panel, combined with a single removable panel, though these can be done. Consideration must be given to the standard rules of wiring multiple panels of varying sizes, outputs, (and even age), in series or in parallel, and the resultant panel output and the charge controller requirements. Some solar panels can easily bend and conform to the rear curvature of the 560; the Sunware product, though flexible to 3%, can not, and would require a contoured plastic base with a rounded underside and a flat top. All of this is another topic.

At any rate, the benefits to this single 100W panel system, as I see it, are:

1) on-the-road-battery charging, so when you get to your site, you are at 100% charged, and not 85% or less. (Even though the flat orientation is not 100% efficient, the panel is generating a current in a mid-day sun with presumably no shadows cast on it, and it only has to top off the battery's last little bit that the alternator and trailer battery charger can't do. Eminently achievable over normal travel times on the road)
2) Being able to orient the panel optimally toward the sun, or out of a shadow without moving the trailer, and resultant improved performance.
3) It is light weight (10lbs for the Sunware and 5lbs for the Renogy vs +20lbs for standard panels, which helps when moving it on and off the roof, or propping it up.
4) Low profile. Won't adversely affect mpg and doesn't stand out to thieves. Stainless frame covers the sides of the plastic base and would blend seamlessly with the rest of the trailer.
5) Optional security hardware can improve theft resistance and 4 bolts is easy to manage by the owner. In fact, only one or two have to be tamper-resistant, and the others can be a quick-release design, such as a bolt placed upside down with a wing-nut securing it on top. As long as yoyo after 10 minutes of fiddling can't walk away with it tucked under their arm, you'll likely never be at risk of losing it to casual theft in a Denny's or Piggly Wiggly lot. Long-term parking, such as at a trailhead on an overnighter, and you can throw it inside the vehicle or the trailer.
6) Off-trailer placement with an extension cable can greatly improve performance and utility of the panel.
7) Panel defect, damage or warranty replacement is simple and doesn't involve "ungluing" it from the roof
8) No mounting holes in the roof of the 560, save for a cable that will discretely follow the roof line edge and enter through the galley hatch skin, where the charge controller will be mounted (possibly) and readily viewable. There is quality waterproof, and aesthetically-pleasing, marine hardware available for this specific purpose of cable management through deck surfaces.
9) I haven't done the mock-up, but believe that the side entrance tent will not shade or interfere with the placement of a panel of this size on the flat section of the 560. If it does, you just flip a corner back while the sun is out and reconnect the strap later.
10) It doesn't preclude incorporating a larger panel in the design, or the possible future addition of smaller fixed panels in the areas to the side, or to the back of the fan vent.

Thanks for reading this far. My other posts haven't been quickies either. I'm open to suggestions/comments on the above, as well as ideas on solar charge controller placement and wiring considerations, which I haven't quite settled or touched on here. Of some concern to me is getting the solar controller and the trailer's battery charger 'talking' to each other in a civilized voice, and not having one in Float while the other is in Bulk mode. Or assuring me that me it doesn't really matter on a simple set-up like this, and that one controller will eventually 'get'er done' while the other has a nap.

I'm new to solar entirely, mobile or otherwise, so to those who have used/lived/thrived on it with the 550/560 and have some experience... I'm all ears.

Cheers,

Steve

 

Brilliantly written Steve! I have one suggestion only and hopefully an answer to a question.

Taping to the roof. When you do this you will want to make "stand offs" of some sort (probably strips of HDPE) that hold the HDPE sheet up off the roof a small amount. Several reasons I see to do that. First is the fact that the roof on a 560 is not flat. It has a very gentle dome shape to it. This would prevent the panel from pulling down flat so best to raise it off the aluminum roof skin a tad bit. The next reason is it would be trapping moisture against the aluminum roof which will degrade the finish of the metal badly enough to make a big project out of if you ever chose to remove the panel. Raising it off a little bit will let it breathe. The third reason is you may want to configure it just high enough up to be able to slip the front roof strap of the side tent under it when setting up the side tent. Place the side tent roof strap in place when configuring your mounting points for the panel mount.

Your question about the solar controller battling with the camper's internal battery charger. Yes, the two will not play well together. If you plug into shore power and run the camper's battery charger you would have to unplug the solar panel and take it out of the circuit. It really would not be serving any purpose anyhow when on shore power.

One note on this. If using the panel to supplement tow vehicle charging the CTEK may be a good solution for you. It not only functions as a intelligent charger for the tow vehicle's charge line but has solar panel inputs as well and would also be your solar control unit.

Cary

 

Thanks Cary for the quick analysis and suggestions. Exactly what I was hoping for. This isn't the kind of project at which I want to take multiple stabs before I get it exactly right . Or come to regret a couple years down the road.

The stand-offs as you describe are very do-able. And of course you would have designed the trailer with a slight imperceptible crown to assist with run-off. How silly of me not to check with a straight-edge.

The 3M tape is a foam acrylic composite. Not sure exactly how thick, once installed, and how much space it can suck up. Or even what doubling up the tape can accomplish. Probably not enough to compensate for the designed curvature or other surface anomalies as you've described. Further, I don't know about the specifics of heating and molding the HDPE slightly to conform to the roof, and having it retain its shape. Again, probably not practical, and doesn't solve the other issues you've raised. The solar panels themselves aren't a concern as they can bend from 3% (Sunware) to over 30 deg (Renogy).

I can play with the tape/HDPE/aluminum interfaces to see how much total surface area I would need to safely secure the stand-offs and keep the whole contraption from flying off at speed, while still allowing for a breathing space and strap placement. This will be the sticking point (no pun) of the whole project. Less tape area to scrape and clean off in the future (if necessary) is a bonus.

I see that there are on-line YT videos for the CTEK install. If I have any questions/ideas about a general install of this device, I will post separate from this, as I see that there are none yet. Anything specific about my particular set-up and I might be contacting you directly.

Cheers,

Steve

 

Presumably, when installed properly, the CTEK can function as a both a TV battery isolator, AND preventing any current back-flow from the trailer battery to the panels at night. I could be reading this wrong and according the CTEK too much useful functionality. Or not.

I tried to glean from Inn42's informative post on their TV solar panel install, and subsequent CTEK install, but am leery to extrapolate any of that generous information to my TD panel set-up. Our 560 has neither the battery isolator option nor the "solar " option, so I guess that does provide me with a clean slate on the electrical install. Any ideas anyone?

 

or (and?) you could put a second battery under the sink....

Admittedly this doesn't solve the problem of charging from the tow vehicle, but it would give you more days

I like the idea of a GoalZero or some other portable battery solution, to allow us to put the fridge into a bear box if needed (not uncommon in the west).

If I do go the portable battery route, I'm considering a second portable solar panel, so one panel would charge the TD battery and one would charge the portable battery.

(I also need to power a CPAP, so I can't simply solve my camping electricity problem by replacing the fridge with a cooler and ice.)

 

Alcat: Thanks. Although I understand and have used the mandatory bear boxes in King's Canyon and Yosemite in the past (and plan on frequenting the area in the future), I hadn't yet stopped to figure out what that would mean for the Dometic at night, or while the site was unattended. The Dometic has a limited OEM 6' cord length. I'm not sure if a higher gauge extension cable will mess with or confuse the Dometic's sophisticated internal circuitry. Or if I really should consider a portable power source supplemental to the trailer battery. Another consideration. (Sigh)

 

Thanks Alcat and Cary. I've solved some of the issues you've raised, incorporated some of the design suggestions, and (surprisingly) enhanced both the simplicity, utility and capacity of the system, without necessarily breaking the bank.

1) I just ordered an 412 WH Ecoflo River lithium battery station: RIVER Portable Power Station by EcoFlow. It has roughly the same capacity of a Goal Zero Yeti 400, but at only 11lbs and the size of a toaster, its smaller, and it has the ability to recharge via car 12V if necessary, unlike the Yeti Lithium (or its flooded cousin and unavailable charge cords). Sadly, though... it is no cheaper. Probably will have lots to say about this unit, after playing with it, and at another time and in another post. But for the purposes of this post: it can extend our Dometic use by nearly 2 days, and as Alcat suggested, provides use of the Dometic at a distance away from the camper or TV, or when you're travelling without the trailer. Or inside a bear box. It also has bonus utility at home, powering electronics, such as our internet router, during a blackout. And its not a chore to lug or store, like a second deep cycle would be. And its safe.

2) I still plan on roof-mounting a panel, but after getting my hands on a Sunware loaner, I now realize that it's robust design, though thin, doesn't need full area support underneath, and that several strips of HDPE plastic used as standoffs, as Cary suggested, will be sufficient to keep it attached. If there is any curvature to the 560 roof, then the 3% flex of the Sunware will take it up and I won't have to worry about 'shimming' it to create a perfectly flat mounting platform. I'll run the stand-offs perpendicular to the long side of the panel, and parallel to our direction of travel. This will accommodate the side tent strap running underneath, as Cary suggested, and provide air-drying of the area. It also addresses somewhat the potential over-heating and resultant efficiency drop-off bugaboos of many thin-flex panel designs. It will still get the security hardware (simple) and stainless frame treatment, if only for aesthetics and not to actually hold it down and keep it from flapping at 70 mph.

3) I won't attempt to top-up the 560's battery while we're on the road, and will just live with what the car alternator gives me. Too many issues, complexity and extra costs associated with multiple charging sources going into just one battery. The CTEK option looks attractive for a variety of reasons, but with our Outback alternator getting the trailer battery up to 12.8V on the road, I don't see it falling into the category of being an under-performing "smart" alternator.

4) The roof-mounted panel instead, when we're mobile, will only re-charge the portable lithium power station by running a cord off the roof and into the cabin, taped down if necessary. When we're stopped, or camped, the same cable can be manually run into the galley, with the hatch open or closed. Then there's the considerable bonus of zero permanent cable mounting on the roof of the 560, or perforations to the skin. If the trailer battery ends up at less than 100% charged after a day on the road, I'm hoping that a decently-sized panel can quickly make up this small difference and top it off after we get to our destination. A simple hatch-mounted solar charge controller for this purpose is not expensive, especially when its not competing with any other charging source.

5) With the extra battery capacity we won't need as a large a panel as the (2' X 4") 100W I originally proposed. Half that size would likely be all that is now necessary. The full battery capacities (about 110 ah combined) alone would allow dry-camping of 4 to 4 1/2 days, conservatively estimated. Intermittent and alternating solar charging of both batteries with a 50W panel over that same 4 1/2 day period could easily extend our dry-camping time by another day or two, giving us 5 or 6 days before we have to pull up stakes. Plenty. How much cold food can the Dometic hold?

5) A 50W thin is far easier than a 100W to handle , prop up, move around, and stash under the mattress when you don't want (or need) it fixed to the roof. And cheaper. I need to save some dough somewhere in the system to pay for the River.

This stuff is on order. It will be a while before I get my hands on all of it and even longer before its fully installed and field-tested, especially with the snow starting to fly. I will update when appropriate. Thanks for reading, and the input.

Steve

 

I ordered a similar device just prior to picking up my teardrop (#904): https://www.amazon.com/gp/product/B01M260BAN/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

Along with a 105 watt solar panel: https://www.amazon.com/gp/product/B01M8LCDN2/ref=oh_aui_detailpage_o05_s02?ie=UTF8&psc=1

It's been really nice while boondocking. I use it to keep my gadgets recharged (bluetooth speaker, lights, phones, watch, batteries for drill) and also to provide power for the coffee grinder. Frankly, I've never discharged it enough to need to use my panels - perhaps if I do a weeklong trip to Assateague (no hookups there).

Having burned through a number of 12volt lead based batteries with my trolling motor and canoe, I have this aversion toward using the house battery too heavily. The main draw I have is the fan - I'm not sure how many nights one could use the fan but haven't wanted to test it either. During orientation, Cary mentioned that you can shut off power from the main house battery and then by plugging power in to a 12 volt socket, you can feed power back into the system. I haven't yet tried this but probably will when I do a longer boondock as I am configured to recharge the portable battery with solar but don't have it set up to do the house battery.

In spite of appearances to the contrary with the fancy batter/solar set up, keeping things as simple as possible with my rig (ie the minimum amount of things to worry about breaking) has been my guiding principal. For this reason, I deleted both the propane and water with my build. I did cave in to comfort though and ordered the AC option which I'm really happy I did. It's really nice to be cool and not humid when it's hot and humid outside.

The answer for me to keeping my food cold is one of the fancy new design ice chests. I got both soft and hard sided ones from Rtic when they had a sale going. For weekends I use the soft sided one since it's lighter and easy to lug around. For longer trips I use the hard sided ice box. Refreezable gel packs work well for weekends and keeping food/beer cold. I've found the double sided steel water bottles to do the trick in terms of ice water. I have 3 of these (1 gallon total) which has worked well for my wife and me on weekends. For longer trips, we have to buy ice every few days but it isn't really a big deal for me as I want ice anyway in my drinking water and I will use the ice melt as drinking water (best to put a plastic container into the ice chest and then ice into the separate container).

Since all of this gear is essentially totally separate from the camper, I usually set up my kitchen space around the picnic table which keeps all of the grease, smell and food scraps out of the camper.

I don't mean to hijack the thread but just thought I'd throw in a different perspective on keeping things simple if you're still in the planning stage.

 

Ben: You're not hijacking. Its all relevant if any of us want to extend our time in one spot, have a CPAP or other greater electrical needs, or wish to avoid... or simply can't access... the more established campgrounds that provide electrical services. And... you wish to keep things 'simple' by counter-intuitively adding more expensive stuff. I know that some might be rolling their eyes at all I've suggested, given all the amenities and capacity that come with a off-the-line CI.

We also have a Yeti35, but I was unsure about how often, or how convenient it would be, to take both to extend our time out there. i.e. initially using the Yeti with ice, and the Dometic unplugged as dry food storage, and then reversing their roles after the ice has melted.

Perhaps I was distracted by a squirrel during that part of the orientation... but are you saying that by taking the trailer battery off-line (disconnecting at the main rotary switch) when the battery has been depleted, and plugging another 12V battery source into any one of the 12V sockets, then all the 12V system (pump, fan, USB sockets, lighting) is live and operable?

If that's the case then the flexibility and utility of this triple-recharging/ double-battery system just increased by 150%. Or something like that.

 

Steve,

You are exactly correct on using the master battery switch when connecting external battery sources via a 12v socket. This eliminates any mismatched battery string concerns. Using a "pony battery" for extended stay is really a method we highly recommend. Keeping the pony battery charged is probably the only real challenge to that concept. There is a good thread on this forum talking about vehicle mounted charging systems for pony batteries you may want to delve into.

Cary

 

Just read them. So... would a +400 Wh 12V lithium power station, like the Goal Zero or Ecoflo be an electrically compatible fit as a 'pony'? Assuming, of course, that the installed trailer battery has been disconnected from the system. One would think it would be even better than a standard lead pony battery (size, weight and capacity considerations put aside) especially if you're now able to monitor the lithium's remaining capacity and draw, which I presume you wouldn't be able to do with a standard lead pony, with both or either of the trailer voltmeter and Trimetric being taken out of the equation.

 

I think lithium battery station should work just fine. Here is what I bought to connect mine to the trailer: Amazon.com: KUNCAN 4FT 12-24V Double Male to Male Cigarette Lighter Plug Extension Cable, with LED Lights, 16 AWG Heavy Duty Cable, Power Charger Cord, Fuse 10A: Automotive

It will be a lot easier to recharge the "pony" than the house battery for me as I can pretty easily carry mine to a sunny spot to recharge. It will also charge via 12 volt in the car or if you are at a campground without electric but a camp store with electric - they may well let you charge that way too. I'll have to try using it this way to see how it goes.

I wonder if you could get by with using the external lithium battery as your primary battery for the dometic rather than your house battery?

 

That fused connector should work fine. The lithium station also has some internal protections in case I get stupid and turn on absolutely everything in the trailer and exceed its 500W capacity.

The lithium (Goal Zero or Ecoflo) has only half the amp hours of the trailer battery. But combined that's plenty and I can see switching the Dometic seamlessly between the two. I'm not a fan of running the Dometic inside the galley with the hatch closed, either mobile or stationary. So being able to place it elsewhere where its cooler or with better ventilation and on another power source is nice.