Any solar installs on FC28 with 2 AC units?

[Kalashnikov]

*sigh*


Finally had time to measure and the weather cooperated.


The current thinking:

- I'm stuck using the 100W compact Renogy panels everyone's been suggesting. The available space is much narrower than I expected, these panels will fit well.

- If I decide to cover vents by using tall feet I could fit 8 panels total. But - I'd rather not do that since they'll be riding very high.
- Some shading seems unvoidable due to the abundance of AC units (I should count my blessings, right? )
- I can either go with 5x panels in parallel like Hermes, he has the same roof layout
OR
- I can go with 6x panels in series-parallel without covering vents. It would look like the diagram below. Haven't yet decided what order the strings would be wired (All across from each other? Or the front pairs linked per side and the back pair wired across?)

[Kalashnikov]

Been pondering my 6-panel drawing above.


Found this post: (see bolded part)

https://community.victronenergy.com/...-differen.html

The voltage output of a shaded string changes minimally with shading. It's current output, and subsequently its power output changes drastically.
The shaded string might not contribute power but it doesn't conduct and drag things down either.
So being shaded it acts like it is not even present, and the MPPT behaves as if there is two strings instead of three.
Shading, is akin to difference in tilt and direction between like panels. It is a misconception that the whole array has to match in both tilt and direction for a single MPPT. The panels only need to match in tilt and direction within the same string, but differently tilted/directed strings of the same number of like panels can be paralleled to a single MPPT.
This can be used to your advantage, differences in string power production can be used to make a longer solar day at full production, say be combining over-paneled East and West facing strings.
In the morning, the East panels work, in the afternoon the West panels work and at noon they both half work, all the while never over-powering the MPPT.
Or alternatively, if you had fixed shaded (say by a chimney) that would definitely shade at least one string at a time as the sun traversed the sky all year, you could add an extra string, to top up production.

Thus in series-parallel this seems like an acceptable layout:
String1 = The two panels at the very front of the trailer
String2 = The two Left side panels next to the ACs
String3 = The two Right side panels next to the ACs


During operation I'd expect String1 to always do the heavy lifting, it would seldom be shaded. During morning/afternoon I'd expect String2/String3 to switch load from one to the other as AC shading took effect. I'd always have at least 400W unshaded while 200W was partially shaded. This is assuming that AC shading only has an impact when the sun sweeps between Left and Right. If it sweeps between Front and Back I'm ok under all circumstances.


Experts, does this sound like a plan?

[AirMiles]

Originally Posted by Kalashnikov

Been pondering my 6-panel drawing above.


Found this post: (see bolded part)

https://community.victronenergy.com/...-differen.html

Thus in series-parallel this seems like an acceptable layout:
String1 = The two panels at the very front of the trailer
String2 = The two Left side panels next to the ACs
String3 = The two Right side panels next to the ACs


During operation I'd expect String1 to always do the heavy lifting, it would seldom be shaded. During morning/afternoon I'd expect String2/String3 to switch load from one to the other as AC shading took effect. I'd always have at least 400W unshaded while 200W was partially shaded. This is assuming that AC shading only has an impact when the sun sweeps between Left and Right. If it sweeps between Front and Back I'm ok under all circumstances.


Experts, does this sound like a plan?

Yes! That sounds like the plan I would use in your situation. Always have 400W and between 10am and 2PM (peak hours) have 600W. Even though my panels are all wired across from each other, I have a similar situation. I always have a possible 400W on the four corners, and sometimes when the one shaded panel flanking the A/C is in the sun I have 600W. During peak sun hours you will have a potential 45A of charging and on the fringe hours you will have a potential 30A of charging. Assuming 4 hours at peak, and 4 hours at fringe, you will have 300AH of "potential" charging each day. 4x45A+4*30A. That should be plenty to keep your batteries charged.

[wulfraat]

Originally Posted by Kalashnikov;

- If I decide to cover vents by using tall feet I could fit 8 panels total. But - I'd rather not do that since they'll be riding very high.

They really don't stick up very high when you cover the vents (you can see in the photos I posted). The bathroom and shower vents "tuck" under the panels - rememberer the interior of the panels has a void, they are not as deep as the frame.

I would go for 8. Do it once, you may have more power generation than you need at high-noon on a sunny day in June.... but on a cloudy day in March you will be thankful for having 33% more generation as compared to 600w.

My panels are all in parallel. I really don't get much if any shading from the AC shrouds.

[AirMiles]

Originally Posted by wulfraat

They really don't stick up very high when you cover the vents (you can see in the photos I posted). The bathroom and shower vents "tuck" under the panels - rememberer the interior of the panels has a void, they are not as deep as the frame.

I would go for 8. Do it once, you may have more power generation than you need at high-noon on a sunny day in June.... but on a cloudy day in March you will be thankful for having 33% more generation as compared to 600w.

My panels are all in parallel. I really don't get much if any shading from the AC shrouds.

I don't disagree with putting as many panels on your roof as you can. But, we have been talking about using the solar prewire. 600W configured in series-parallel is the maximum that can be installed on the solar prewire. If you decide to do 800W, a new combiner box is needed and larger wire between the combiner box and solar controller. Its not the cost of the combiner box or wire that's the issue. There's a little additional labor. But most importantly to me is that you need to start drilling holes in your Airstream. By using the solar prewire, I didn't have to drill a single hole. If you plan to keep your Airstream forever, no one will care if its full of holes. But if you decide to upgrade your Airstream, its better if you didn't drill holes.

I never expected to trade my 25' for a 27' after two years. But plans change. I'm glad that I used the solar prewire and didn't spend a lot on adding solar that would have actually damaged the trade-in value of my Airstream. The dealers offered me nothing for my solar. One "highly regarded" dealer actually deducted value because it would have residual caulk on the roof when I said I'd remove the "worthless" solar installation. In my experience, dealers do not like "improvements" made to an Airstream.

[wulfraat]

Originally Posted by AirMiles;

But most importantly to me is that you need to start drilling holes in your Airstream.

Completely agree - don’t drill, no roof penetrations.

My combiner box is located right next to the fridge vent. Lewster, who did my install, came through the fridge vent with 4ga wire. No holes in the roof [emoji4]

He also used 3M VHB tape and silkaflex to mount the panels - no drilling.

Its a wonderful thing when you are silently delivering 60A using the sun to the 600ah battery bank [emoji4]

These are big installs one way or the other.

[AirMiles]

Originally Posted by wulfraat

Its a wonderful thing when you are silently delivering 60A using the sun to the 600ah battery bank

On this part we totally agree! 45A to a 230AH battery bank is not bad either. What I find is that I use up to 10A per hour. During daylight hours, I use 10A while up to 35A goes to the batteries. At dark, I have a fully charged battery. I can continue using 10A for a few hours and then let the furnace, or fantastic fans, run all night. The next day the cycle is repeated.

I typically do not have problems on overcast days. They are usually bright enough to charge my batteries enough to get by without additional generator charging. I only have issues recharging my batteries if I choose to park under a nearly complete canopy of trees or on days with dark clouds and heavy rain all day. I try to avoid both heavy rain and tree canopy. When I can't, I may need to give the generator a few hours of exercise. I've only exercised my generator five times in 250 days of solar use. I will conserve "a little" when I know that its a poor solar day. I hate the sound of a generator.

[wulfraat]

I hate the sound of a genset too!

10a sounds about right. I pull a little more on average.

I think the only difference between our usage patterns is that I run a 120v sonic ice maker non stop and I like to run the air conditioner for an hour or two per day either at lunch stops or at the campsite. Takes the edge off sometimes. And I like the little jewel ice with my bourbon at the end of a long day [emoji4]

Otherwise I wouldn’t have such a large battery bank / solar array. But you only live once right?

[AirMiles]

For example, here is a link to 30 days of solar usage with 600W on the solar prewire. Almost every day was overcast during that 30 day period from mid-September into October in North Carolina and Northern Alabama. My batteries floated on 17 of the 30 days. On four of the 30 days, my system produced less than 450W. But luckily production on the following day was typically about 1kw which saved me from ever needing the generator. My battery bank is small at 230AH and is only good for one day without some solar charging. As you can see I get enough charging on overcast days to get by most of the time. Some of the days were rainy, which are probably the ones where less than 300W was produced. I can't wait to spend some time this summer under sunny skies with my 600W of solar.

http://www.airforums.com/forums/f448...ml#post2299311


Reply to Wulfraat: Its hard to use over 10A in an Airstream unless you are running a hairdryer or some other energy hog with the inverter. My DC refrigerator can use 14A almost continuously. I've learned I cannot operate my refrigerator on 600W of solar and a 230AH battery bank. I don't think any Airstream has enough roof space to produce 14A of almost continuous load for just the DC refrigerator.

[wulfraat]

Originally Posted by AirMiles

Reply to Wulfraat: Its hard to use over 10A in an Airstream unless you are running a hairdryer or some other energy hog with the inverter. My DC refrigerator can use 14A almost continuously. I've learned I cannot operate my refrigerator on 600W of solar and a 230AH battery bank. I don't think any Airstream has enough roof space to produce 14A of almost continuous load for just the DC refrigerator.

If I typically leave the multiplus on 24/7 that’s about 2.0-2.5A overhead. My ice maker averages about 4A over a 24 hour period. So that’s 6-6.5A without anything else whatsoever.

I’m typically 7.5-12.5A draw durning the day (about 4-5A in the off hours at night) or so depending on what all else is running off DC.. like the fantastic fan, LP fridge, upgraded sound system, TV, internet/router, movies, lights, etc

I enjoy the convenience of “full-time residential power” so I typically keep my multi running 24/7 I’m typically averaging 150-200ah/day in energy consumption.

Panels will generate 1.5-2.5kwh on an average day and between 3-4kwh on a sunny day in June to replenish the bank.

[wulfraat]

Originally Posted by AirMiles;

Reply to Wulfraat: Its hard to use over 10A in an Airstream unless you are running a hairdryer or some other energy hog with the inverter. My DC refrigerator can use 14A almost continuously. I've learned I cannot operate my refrigerator on 600W of solar and a 230AH battery bank. I don't think any Airstream has enough roof space to produce 14A of almost continuous load for just the DC refrigerator.

If I typically leave the multiplus on 24/7 that’s about 2.0-2.5A overhead. My ice maker averages about 4A over a 24 hour period. So that’s 6-6.5A without anything else whatsoever.

I’m typically 7.5-12.5A draw durning the day (about 4-5A in the off hours at night) or so depending on what all else is running off DC.. like the fantastic fan, LP fridge, upgraded sound system, TV, internet/router, movies, lights, etc [emoji4]

I enjoy the convenience of “full-time residential power” so I typically keep my multi running 24/7 [emoji4] I’m typically averaging 150-200ah/day in energy consumption.

Panels will generate 1.5-2.5kwh on an average day and between 3-4kwh on a sunny day in June to replenish the bank.

All that being said my data sample size is not nearly that of AirMiles [emoji4]

[Kalashnikov]

Realistically my wife couldn't handle much boondocking. We've dry camped many times before (and she didn't even notice ) and it's a fantastic way to open up more camping opportunities but she likes the security of staying near civilization. We'll be on full hookups 50% of the time and occasionally do trips of 3-4 days dry camping. No hair dryer, curling iron, toaster, microwave, ice makers, video games, heavy TV watching, AC use. We just need lights, occasional TV and the furnace. And we want the system to not rely upon a generator mostly due to the noise factor.



Thus my power needs don't justify going beyond 600W of solar. I've installed a pair of Trojan T105 batteries and have no plans for Lithium. The Trojans can only handle about 29A of charging current. 400W would likely be adequate, 600W is hardly any additional effort or cost. 800W would be a larger project.


References:
https://www.altestore.com/blog/2015/.../#.XiQ_nhd7k6g
https://www.trojanbattery.com/tech-s...y-maintenance/


The Alt-e site recommends solar array size 315W-787W, my proposed 600W setup seems to be optimal. Indeed I wish to use the factory wires since they are adequate for the 600W particularly if driven with a higher voltage and it will save me some time.


I'm about to pull the trigger on my Amazon shopping cart. I still need to sort out:
- What are the best mounts? I like a combination of the Renogy flat and curved mounts but OTOH I'd like to keep the panels removable. I may make my own or go with the AM $olar mounts
- How much extra wiring do I need? Assume MC4 throughout, SAE at the end
- What switches, shunts, other components? (Haven't read my PMs yet, thanks to those who wrote back)

[AirMiles]

Originally Posted by Kalashnikov

References:
https://www.altestore.com/blog/2015/.../#.XiQ_nhd7k6g
https://www.trojanbattery.com/tech-s...y-maintenance/


The Alt-e site recommends solar array size 315W-787W, my proposed 600W setup seems to be optimal. Indeed I wish to use the factory wires since they are adequate for the 600W particularly if driven with a higher voltage and it will save me some time.


I'm about to pull the trigger on my Amazon shopping cart. I still need to sort out:
- What are the best mounts? I like a combination of the Renogy flat and curved mounts but OTOH I'd like to keep the panels removable. I may make my own or go with the AM $olar mounts
- How much extra wiring do I need? Assume MC4 throughout, SAE at the end
- What switches, shunts, other components? (Haven't read my PMs yet, thanks to those who wrote back)

1) That battery maintenance sheet from Trojan is EXCELLENT! I bookmarked it and will use it in the future.
2) What mounts? Am$olar's are the best but yes they are expensive.
3) How much wiring? 50' of 10G duplex should be adequate. I bought 50' and have about 12' extra. I prefer AmSolar's 10-2 duplex: https://amsolar.com/rv-cables/cable-10ga-2-gry 6' of 6G 10-2 should be more than enough between the Victron and the busbars: https://amsolar.com/rv-cables/cable-6ga-2-gry I would not use MC4 connections. I used crimp connections.
4) What switches . . . ? Here is my complete parts list: http://www.airforums.com/forums/f448...ml#post2288472 Anything not on that parts list is available locally at an auto parts store such as crimp connectors.

Have fun with your install!

[AndyKeene]

I am a huge fan of solar and have all of my off-grid shops run by various solar setups. I have posted a few notes about my solar setup for my Airstream in the past. My 2017 27 footer came with the 2 Zamp 100 watt panels and some cheap hardware to control and input the voltage.
My two air conditioning units and the likelihood of damage to the roof of my rig caused me to not add anymore panels to the Airstream....I instead placed 1000 watts of panels, a 6,000 watt inverter-converter, 6 lithium batteries, an 80 amp Outback charge controller and a breaker box with a 50 amp outlet and a 20 amp 110 outlet on my tow vehicle. Under my rear bumper I have the outlet boxes, I simply plug my standard 50 amp service line directly into the tow vehicle and boondock away. Yes, there is a cost but I can replace, repair and handle all the work without ever getting on top of the Airstream.

I now carry an additional 12,000 watts in the bed of my contractor shell to supplement the energy output if we think we may need more, or power another RV that is parked with us.

No running a gas or diesel or propane generator.

How much did it cost to have designed, installed and run. I learned about electricity from my Father as a child and now simply keep up with technology and do it myself for my needs. All the information is out there, readily available from many places. Figure a dollar a watt for solar panels, flexible or solid. Everything else is current market price or what I can find on eBay.

[Timberock]

Greetings wulfraat,

Any chance you can share a ground level photos of your setup to show the right height of panels that are installed over the vents?

Thanks in advance for any effort this takes!

[Hermes]

Originally Posted by wulfraat

Completely agree - don’t drill, no roof penetrations.

My combiner box is located right next to the fridge vent. Lewster, who did my install, came through the fridge vent with 4ga wire. No holes in the roof

He also used 3M VHB tape and silkaflex to mount the panels - no drilling.

I have exactly the same type of installation: no holes drilled anywhere on the roof. Used AM Solar feet for the 5 Renogy panels (VHB taped with a Sikaflex covering over and around each foot), 4 ga wire from the combiner box through the fridge vent (drilled two holes on the side of the vent to install two AM solar Liquid Tight Srain Reliefs for the + and - 4ga wires) and the combiner box was VHB taped and Sikaflexed. All panels are wired in parallel to the combiner box with 10/2 wiring through AM Solar Liquid Tight Srain Reliefs, and from there, I drilled the floor (plywood) of the back of the fridge cabinet to connect the two 4ga cables to the MPPT controller in the front of the trailer under the L couch. Connected the controller temperature sensor to the battery bank, the current shunt (500A/50mV) with a shielded twisted pair to the monitor, and then connected the MPPT controller output (4 ga cables) to the battery bank and it all worked!

I would not configure my solar system on the basis of the wiring that is already there. When that wiring was installed, assumptions were made on what the average customer would need. If you fit the profile, fine, if not, then configure your Airsream according to your needs and expected needs (especially if you appreciate boondocking or off grid camping).

[AirMiles]

Could the factory prewire be used with 600 watts of panels wired series/parallel, making the equivalent of two 300 watt panels or three 200 watt panels?

Short answer:
YES because the key is to do series/parallel groups of panels. 600 watts in three sets of two 100W panels would work great! By my calculation below in the "long answer" is that this configuration would be capable of producing 588 watts to the controller for a total loss of only 2.0%.

Long answer: http://www.airforums.com/forums/f539...ml#post2208101

[Hermes]

This video is worth watching if you are considering connecting solar panels in series:

https://www.youtube.com/watch?v=ofo1HQyGG8s

[wulfraat]

Originally Posted by Timberock

Greetings wulfraat,

Any chance you can share a ground level photos of your setup to show the right height of panels that are installed over the vents?

Thanks in advance for any effort this takes!

Do these help? I’ll probably go camping this next weekend and would be glad to take some close up pics if that helps anyone on the forum.

[Timberock]

Those shots work well to help understand the profile differences of the mounting options. When comparing to other installations in the Solar Show & Tell thread the difference in panel ride height appears to be minimal, especially for those with a goal of installing the panels level rather than following the roof curve.

If you get the opportunity to take a few higher resolution shots on your next trip from either side I wont turn them down though. My family is planning our 2020 road trip now and the number of stops without services will dictate if the solar upgrade comes this spring or later. Regardless the photos are definitely helping with planning as is all the great information shared in this thread.