The "Meg" Build

Lt.Dan

Photon Sorcerer
Hey Y'all, I figure about time to start posting updates on my solar build. As a couple of you may know, I live full time in an RV with my wife, 2 kids (a 2 y/o and a 3 y/o) and an old Pitbull. The RV is a 2020 Grand Design Momentum 381M, we nick named it "The Meg" short for The Megaladon, because of its shear size lol. We named it something aquatic because our other trucks, like my Black 96 F350 is named Shamu, and our white 2018 F350 is named Moby lol.
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We originally moved into it to save some money, and pay off some debt. We also own a Polaris RZR turbo and frequent several offroading places on the west coast and even some further inland, so having our home on wheels to take with us on trips/vacation was a win/win for us. The trailer is almost 45' long, and weighs over 22,000lbs with the RZR and everything loaded up, or roughly 30,000lbs combined. We currently live with some relatives on their horse property, with our own electric meter, gas, water, and septic tank. Now that we have been living in it for around 6 months and "settled in", im ready to start digging into it for an inverter/solar setup.

I have ordered 16x CATL cells from Michael and the group thread for this build, as well as a Smart Daly 200amp BMS. I do plan on another set of 16 in the near future.

I also got an MPP LV6548 from Ian at watts247.com, which it showed up in almost 2 days. Super happy with the build quality so far, and Ian has been awesome to work with on any questions.20210301_202236.jpg


Then I ordered 24x 250watt Snail Trail Panels from San Tan solar and 12x 240watt Sunpower panels from them as well. Which those showed up today.
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The 12x 240watt panels I will be mounting on the roof of the trailer, and the 24x 250 watt Snail Trails I will be mounting on a metal building that we park next to on the property. These will most likely be getting mounted/wired up this coming weekend, or maybe next, we'll see.

I did last weekend mount the inverter in the generator compartment, which worked out super awesome.

This is the 100% factory compartment/wiring except the 2x BattleBorns i have currently. On the left you can see the coiled up white wire is the factory solar wiring from the roof. I have installed 6x Rivet Nuts in place in preparation for the mounting plate I made for the LV6548.
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Then the mounting plate bolted on. I manage a laser/cnc shop, so i designed/fabricated this braket just for this. I will be utilizing our laser/ cnc press brake to make a lot of parts for this build coming up, including a fixture/ battery box for the cells, solar panel mounting brackets, etc. (Excuse the corrosion/ stain on the plate, it was just some scrap i happened to find that was perfect size)
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Then bolted the LV unit to it with more rivet nuts. Made for an easy 15 minute install. I also just laid down some HD VHB double sided tape and mounted an Aims PV disconnect and wired it all together. The inputs run into the propane compartment, then out the bottom to connect to the 2x 6s2p solar arrays mounted on the building I mentioned earlier.
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I have also already wired the AC side of the inverter with a 63a 4 pole Rotary Changeover switch, so I can dictate if I want the single phase output on the inverter to power both legs of the breaker panel, or the 50a Split Phase shore power to feed the breaker panel and bypass the inverter. This allows me to still power the trailer with the grid if something happens to my system, or I have to disconnect it for some reason. But I didn't get any pics of that all wired in yet.

Right now the inverter is on and running, just bypassing power into the trailer, waiting for the batteries to show up.

Now I just need to install the solar panels on everything and wait for the cells to arrive (patiently lol).

I have so much more planned for this. But this is enough information for now lol.
 
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Lt.Dan

Photon Sorcerer
I also ordered the LCD Control Panel and the Capacity Indicator for the Daly BMS on Ebay this morning. I figured for $50 or so, id give it a shot. We'll see how they work 🤷‍♂️
 
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400bird

Solar Enthusiast
Looking good! And fitting name, that thing is huge!

With limited space on the roof, I would have expected higher output panels. That way if you go out away from home or hook ups, you can better support your energy use.

Overall, with 24 panels off the trailer, you've got lots of output
 
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Lt.Dan

Photon Sorcerer
Looking good! And fitting name, that thing is huge!

With limited space on the roof, I would have expected higher output panels. That way if you go out away from home or hook ups, you can better support your energy use.

Overall, with 24 panels off the trailer, you've got lots of output
Thank you! It definitely gets some looks, and being 62' overall length with the truck and trailer, it definitely makes you think about every turn you make lol.

And because there is 3 AC systems, I was limited on the width of the panel, so I called SanTan solar (I am trying to do this entire thing on as much of a budget without sacrificing too much quality) and asked them if they had a panel less than 33", which is the width from my AC to the edge of the roof. The Sunpowrt 240w panels are 31.5"~ so it worked perfect, and they are still very affordable. With 12 of them, it should output 2880 watts at full peak, then take into account .8 factor of real world and any losses, I figure 2300watts is way more than plenty for what we do when off grid. Most of the time spent is outside of the trailer anyways.
 

Freep

Solar Addict
I saw a rig last year when we were out boondocking where the owner had installed a custom rack on his fifth wheel as a platform to mount his panels. The panels covered the entire roof -- above the AC units and vents. This had the benefit of giving him maximum solar collection while also shading the roof and the ACs. The AC is more efficient when it is in the shade.
 

Lt.Dan

Photon Sorcerer
I thought about elevating my panels above my AC unit as well, but 2 things popped into my mind.

1) I'm already at the legal limit of 13'6" tall (go figure the trailer is big in every direction) at the tip top of the AC unit. Almost like they planned it to be exactly that height.

2) I didn't want to create a huge parachute, and cause all these panels to rip off, or at the very least create a huge aerodynamic drag. My 18' F350 already gets 7.5-8mpg towing this thing lol.

I did see a trailer about a year ago on one of the Facebook groups, where a guy had somewhere around 3kw of solar on the roof, and he had plans of creating a frame to "flip out" and create another 2000 watts or so. It was pretty wild, but again, I don't need anything like that.
 

Lt.Dan

Photon Sorcerer
Got the unistrut mounted to the top of the trailer. Over 150 ft of it! It's amazing how much the roof is reinforced and feels much much more rigid now.

Waiting on some stuff to come in the mail tomorrow. Then I can start mounting the panels to the unistrut and wiring it all together. You can also see the roof im mounting the other 24x panels too on the right of the picture.

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I also made custom 12ga (.105") thick Stainless Steel brackets that will attach the panel to the unistrut. The bracket also allows for a small amount of tilt, so I can put a slight rake in the panels and reduce some of the "parachute" effect. More pics to come.
 
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K8MEJ

Solar Addict
You got legs, Lt. Dan!!

I have the much cheaper and smaller sibling, an Imagine 2800BH. The roof construction is likely very similar so I'm hoping you can answer some questions since you're further along on the roof side of the project than I am.

  1. Did you use steel or aluminum Unistrut? It's hard to tell in the picture.
  2. Is that full profile or low profile Unistrut?
  3. Can you describe how you decided to attach it to the roof? What were the length of fasteners, type, etc? Did you only screw into "rafters"?
  4. What size fasteners did you use?
  5. How did you choose to seal the penetrations? Did you use butyl tape under the channel and Dicor for the screw holes?
Pardon the interrogation :) You and I have chatted across various topics so also pardon if my questions are a repeat!
 
Nice setup. My parents have the biggest Montana they ever made and it's no longer made. 6 slides, front living room. Thing is a monster. It lives full time at ocean lakes in Myrtle Beach.
 

Lt.Dan

Photon Sorcerer
You got legs, Lt. Dan!!

I have the much cheaper and smaller sibling, an Imagine 2800BH. The roof construction is likely very similar so I'm hoping you can answer some questions since you're further along on the roof side of the project than I am.

  1. Did you use steel or aluminum Unistrut? It's hard to tell in the picture.
  2. Is that full profile or low profile Unistrut?
  3. Can you describe how you decided to attach it to the roof? What were the length of fasteners, type, etc? Did you only screw into "rafters"?
  4. What size fasteners did you use?
  5. How did you choose to seal the penetrations? Did you use butyl tape under the channel and Dicor for the screw holes?
Pardon the interrogation :) You and I have chatted across various topics so also pardon if my questions are a repeat!
The imagine is still a very nice trailer! Better than a loot of other trailers out there lol.

1. I used regular P1000 galvanized unistrut.
2. Regular 1 5/8" height, I wanted a decent amount of air underneath the panels and room to work.
3. I used 1/4" x 1.5" Stainless steel lag screws and stainless Fender washers. I tried to hit every stud i could find, but its very difficult on an rv roof. I even went and bought a super nice stud finder and it was still very tough. I put 12 lags into each rail, for 48 lags total. Id say about half of them are in the studs.
4. See 3
5. I did dicor only. I initially drilled a 5/32 hole in every location I needed, then flipped the unistrut and laid a decent amount of dicor down, then put the unistrut back and screwed it down, then made about an 1.5" diameter blob over the head for a final seal.

If I were to do it again, I would call Grand design and get plans for the roof ahead of time to be able to find all of the studs, and I would also use a little butyl tape underneath as well.

Hope this helps!
 
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K8MEJ

Solar Addict
The imagine is still a very nice trailer! Better than a loot of other trailers out there lol.

1. I used regular P1000 galvanized unistrut.
2. Regular 1 5/8" height, I wanted a decent amount of air underneath the panels and room to work.
3. I used 1/4" x 1.5" Stainless steel lag screws and stainless Fender washers. I tried to hit every stud i could find, but its very difficult on an rv roof. I even went and bought a super nice stud finder and it was still very tough. I put 12 lags into each rail, for 48 lags total. Id say about half of them are in the studs.
4. See 3
5. I did dicor only. I initially drilled a 5/32 hole in every location I needed, then flipped the unistrut and laid a decent amount of dicor down, then put the unistrut back and screwed it down, then made about an 1.5" diameter blob over the head for a final seal.

If I were to do it again, I would call Grand design and get plans for the roof ahead of time to be able to find all of the studs, and I would also use a little butyl tape underneath as well.

Hope this helps!
I have received drawings from GD for my trailer when I've requested them. Maybe I should ask for the roof drawings, too. I haven't attached my unistrut yet, but it looks fairly easy to see the butt joints of the 3/8" flimsy decking they used. Mine is a 2018 model made in June 2017. This is my fourth summer. Even though I scrub the roof two or three times a year, I can still see darker lines on the roof membrane where those butt joints are underneath. Finding the rafters in between the butt joints will be harder without knowing how far spaced they are. But, since you mentioned the idea, I think I'll post on the GD forums and see if anyone knows for my model.

I'm using aluminium 13/16 strut channel and SS spring nuts. I'm also going to use these: Tilt mounts. I doubt I'll be tilting the panels for max power very often, but I wanted a little extra space under the panels and the ability to tilt them for maintenance, wiring, etc. Like you, I have a max of 33" between AC shrouds to the edge of the gutters. I wanted to be able to pull the shroud off if needed so the tilt mounts will help with that, too. On my TT, most of my vents and AC run right down the center. Off-center I have a skylight over the shower (that I wish wasn't there), the roof vent for the fridge (my fridge is not in a slide out), one Maxxair vent, and a couple of plumbing vents. I can run Unistrut much like you did.
 
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Lt.Dan

Photon Sorcerer
Don't go off the joints for where the studs are. Many of the joints on mine did not have studs below. From reading online, I've seen even GD is terrible at roof construction. Some studs being 32-48" apart on some trailers!!

Most of the placements I chose based on this already in the roof, like there is always a stud on either side of the AC, and more than likely around the vents etc.

We also jumped a little on the roof, and you could tell where the roof was more solid (from studs underneath) than other spots. Which gave you a good idea where one should be.
 

Lt.Dan

Photon Sorcerer
From yesterday. 3 more done. I grabbed my multimeter and checked when I got home from work at about 4:30. Sun wasnt very high but wasn't low either, and 1 panel was 1/2 shaded from the AC unit (you can see it in the pic). 133VOC and 7.12amps short circuit checking it with my clamp meter. Roughly 950 watts, not bad.

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And today, just before running out of wire. I've used 100ft of both black and red. I need another 15 or 20ft or so to wire in the last 3 panels. The only ones remaining are the 2 on the left and the center one that is closest too me in the pic. I ordered another 100ft of each color to finish.
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Bud Martin

Photon Sorcerer
From yesterday. 3 more done. I grabbed my multimeter and checked when I got home from work at about 4:30. Sun wasnt very high but wasn't low either, and 1 panel was 1/2 shaded from the AC unit (you can see it in the pic). 133VOC and 7.12amps short circuit checking it with my clamp meter. Roughly 950 watts, not bad.

View attachment 44088

And today, just before running out of wire. I've used 100ft of both black and red. I need another 15 or 20ft or so to wire in the last 3 panels. The only ones remaining are the 2 on the left and the center one that is closest too me in the pic. I ordered another 100ft of each color to finish.
View attachment 44090
I love those used Sunpower panels, I have four SPR230 and they are working great, I wish I can locate more of them.
 
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Lt.Dan

Photon Sorcerer
SanTan seems to go through them pretty quick. Every time I talked to him in the last 6 months, he had the same model in just a different wattage. Some 210w, some 240w, and 250w. He just happened to have 240s coming in when I called.

I gotta admit, they are super well put together. Very strong and sleek panels.
 

Lt.Dan

Photon Sorcerer
No progress as of late, but I am revisiting the 12v side of my build, as I do have some 12v loads.

Lights
Water pump (when boondocking)
Leveling system (80amp DC motor)
Starting the Generator (when boondocking and need to charge the batteries at night or something, but will be very rare)
Stereo
Fuel station
Bunk beds in the garage
Airxcell Roof vents
Etc

Now everything except the leveling system and starting the generator can be run off of a small buck converter, but starting the generator especially requires too many amps.

So I've kind of dug myself into a hole where I have to have a 12v battery on board. Good thing is I have 2x 100ah Battleborns that I bought before I knew what I was doing lol.

So, I can leave the Progressive Dynamics PD9160ALV (85-90% efficiency im guessing, can't find any stats for it online or in the manual) that I already installed to charge the batteries, and run them off the LV6548 (93% efficiency). That sounds pretty inefficient if you ask me.

I could get a smaller 10a Victron smart battery charger, (which is what battleborn actually recommends I do) that has much higher efficiency, but also has to run through the inverter.

Or install a variable buck converter (which i have a 30a buck converter already that i could program to a designated voltage and hardwire it). This has a much higher efficiency, and only goes through one unit instead of two. (Claimed 92-96% efficiency). Only downside is it is straight from China, and I do not know how reliable it is, and if it might someday fry the battleborns from high or low voltage somehow (even though the BMS should protect it, I don't want it sending 40V through my trailer somehow).

Any ideas/suggestions/recommendations/concerns?
Thanks guys
 
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K8MEJ

Solar Addict
This is partially why I opted to stick with a 12v system, even though it would have been nice to go to 24v. I didn't want to run large (or multiple in parallel) DC-DC converters. However, I did consider the Victron converters that have parallel capability. With my all Victron system that would have been easy to integrate, but added another potential RFI source for my ham radios. So I stuck with 12v.

In your case, go have a look here. I'm sure there are other manufacturers that would be similar. You could use something like this along with 12v batteries to run a 12v system or this and not keep 12v batteries. I don't know what your system voltage is so if you're running 48v then you'll likely need something different.
 
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Lt.Dan

Photon Sorcerer
This is partially why I opted to stick with a 12v system, even though it would have been nice to go to 24v. I didn't want to run large (or multiple in parallel) DC-DC converters. However, I did consider the Victron converters that have parallel capability. With my all Victron system that would have been easy to integrate, but added another potential RFI source for my ham radios. So I stuck with 12v.

In your case, go have a look here. I'm sure there are other manufacturers that would be similar. You could use something like this along with 12v batteries to run a 12v system or this and not keep 12v batteries. I don't know what your system voltage is so if you're running 48v then you'll likely need something different.
I'm running a 48v system. And the only reason I am hesitant to go to a DC to DC converter is because none of them are smart charging. When talking with battleborn, we determined that they would hold the 12v Batteries at too high of a charge voltage for far too long, and cause battery degradation. Hence the suggestion for the 120v victron 10a smart charger, because it is a 3 stage charger and won't hold it at a high state of charge for extended time.

Another thought I have, which I am completely ignorant when it comes to this, but what happens when you try and turn a 12v starter with a 48v battery? Will it burn it up?

I did find out onan recommends 450 cranking amps to start the generator.
 

Lt.Dan

Photon Sorcerer
Running some tests on the LV6548, trying to see what we will be able to run once we finally start using it. I currently have about 200-250watts at idle from the fridge running on propane, lights, etc. I have a 50" Samsung smart tv pulling 150 watts and all 3 ACs running on High and this was my results:

4630watts
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72% load
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This is the only one I'm concerned about. 110v instead of 120v. Granted this is in bypass mode, so im curious if this is the voltage from the grid that is being pulled down, or if the inverter is taking grid power, and running it through the inverter and its dropping? Don't forget we are running in single phase, so all of this is only on 1 leg, which would explain the voltage drop.
20210410_142419.jpg

This also shows how many watts the ACs are consuming. If I take 4630 watts, subtract my baseline of ~430 watts, then 4200watts split to 3 units (if they are all drawing the same power, which they should be close as they are all the same Coleman Mach 15), equals 1400 watts each. Not bad for a 15000 BTU RV Ac. But its also only about 75* outside, so they arent working very hard.

I'm also pretty stoked how the trailers EMS (energy management system) keeps the 3 ACs from cycling at the same time, so no 2 compressors are starting at the same time, reducing surge power required.
 
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