Is there an optimal panel string layout?

[TravelSolo]

Looking at getting a new 37ft 5th wheel and putting 1400-2000W on the roof. Probably two strings on independent SCCs, each probably series-parallel.

My question is, anyone think driver-passenger arrangement is better than a front-rear setup for the strings? Maybe it's a wash as I can't really think of why it would matter if the arrays are the same size

Just as an example so don't mind the odd number of panels in the groups, but is red or green better? Or it only matters based on where the shade comes from? I don't think the panel angles closer to the nose will cause too much variation in output

[pasdad1]

I think it matters where the shade comes from

[TravelSolo]

Originally Posted by pasdad1

I think it matters where the shade comes from

for sure but i am trying to determine if there is some other "logic" to apply such as probability of tree cover/shade at a site at a campground being less at the front of the space than the rear, which would make the red option better. Or are there other common situations that would have a slight improvement in output.

admittedly this is more of a thought exercise than anything

[xc-mark]

location of AC units would be helpfull. Honestly I have 1920 watt on our roof and rarely see over 1300 watt unless its noon time and mid summer. Panels that are flat just dont produce what there rating. During winter I am luck to see 300 watts for 3 ~4 hours .

[AllegroD]

Originally Posted by xc-mark

location of AC units would be helpfull. Honestly I have 1920 watt on our roof and rarely see over 1300 watt unless its noon time and mid summer. Panels that are flat just dont produce what there rating. During winter I am luck to see 300 watts for 3 ~4 hours .

And all other things on the roof. Antennas, vents, fans, etc.

[Lv2Roam2]

I have eight panels on a 43' roof, and 3 A/Cs - 2 roof vents, 2 tank vents, sat antenna, etc. It's walkable but tight. Some placement thoughts:
- May be impacted by where you penetrate the roof to bring wiring in
- Putting 2 junction boxes to separate controllers will give you redundancy, manage loads, reduce long wire runs, and possibly keep all/most wiring under the panels
- It's worth getting raised mounts (to keep panels cooler) and allow tilting with add-on bars (AM Solar has a system that works well - significant power gains when boon docking longer periods)
- There are some 'slide-out' mounts for panels (2 panels stacked - one slides out over the side of the RV when parked)
- Recommend wire looms to cover exposed lines - in 5 years the sun did a fair bit of damage to wire sheathing

[Yosemite77]

I have 6 - 200w panels on our 35 ft 5er. With how they are laid out, I still have room for another 2-3 panels. As long as you plan ahead (which you are), I doubt you’ll have trouble fitting them.
Before researching panels, I’d start by making a very detailed map of your roof, locating the ac units, vents, etc. Odds are your trusses are 16” on center. You’ll want to make sure to locate panel brackets to hit those. Keep in mind you’ll need to clean the panels, so you might want to leave some space for a narrow walkway to navigate around the roof. Best of luck!

[oldenavy]

Originally Posted by TravelSolo

Looking at getting a new 37ft 5th wheel and putting 1400-2000W on the roof. Probably two strings on independent SCCs, each probably series-parallel.

My question is, anyone think driver-passenger arrangement is better than a front-rear setup for the strings? Maybe it's a wash as I can't really think of why it would matter if the arrays are the same size

Just as an example so don't mind the odd number of panels in the groups, but is red or green better? Or it only matters based on where the shade comes from? I don't think the panel angles closer to the nose will cause too much variation in output

Is your plan to only have two parallel strings? If you have 10 panels as in your sketch, why not 5 strings of 2 series panels each? As you are probably aware, more parallel strings gives you more “shade resilience” at the cost of heavier duty wiring and more line losses. It’s all a trade-off, there’s no single correct answer.

On my last trailer, I had 6 x100w panels on three strings feeding a single MPPT controller. With 300Ah of LFP batteries, I never had to plug in unless I wanted Air Conditioning.

[Captain8]

I think drive-passenger is a better setup because a bit angled and one side would get better light than the other at times so output will be better. This only matters if they're on different controllers.

I have 3000w of solar in groups of 5 100w panels but only have 1 controller. I did 3 groups on each side

[astrnmrtom]

Two types of shade you'll encounter, one is shading by what's on your roof, and the other is shading from the environment. The first you have more control over, so work with that one first.

We've been full timing for almost three years now and have camped in a lot of different places, from wide open desert, to completely treed over, and everything in between. My original system had panels on one side, and when we planned our boondocking or camping without power, we'd Google Earth the campgrounds to select the best sites if possible. Now, with panels on both sides, it doesn't matter nearly as much.

I do have an on board generator and a small portable, as backups so I'm good in any conditions.

In the winter, tilt brackets make a significant difference. I have 6 panels in 2s3p configuration with a single controller, and it's worked well.

Unless you camp in the same places, your local environment will vary a lot. If you plan ahead, and use Google Maps satellite view, you can have some control.

I did my own system and decided to use tilt brackets. While I've only used them a handful of times, they are always there should I need.

So, I'm in the group that says do what's best for your physical set-up. You have much less control over your environment so that much less of a factor.

[Glad2bhere]

We only had room for 3 60 cell modules on the roof because of all of the stuff but still have 735 watts total. All in parallel through a Victron 60 amp charge controller to 6 GC2 FLA batteries. During bad weather I'll usually run the generator for about an hour in the morning to get through the bulk charge stage (also a good time to use the coffee pot and toaster) and still have enough solar for absorb and float stages before dark.

[TravelSolo]

Originally Posted by oldenavy

Is your plan to only have two parallel strings?

Two separate runs in a 2S3P or 3S2P config for each run. It all depends on what panels I can fit and what roof top items actually present once I get a new trailer. Regardless of the number of panels, if even number on each SCC, then it will be series parallel in some form. If I need to I can add a smaller third SCC if panel counts work out that way.

Originally Posted by Captain8

I think drive-passenger is a better setup because a bit angled and one side would get better light than the other at times so output will be better. This only matters if they're on different controllers.

I would do multiple controllers. For both redundancy and maximized output if I decide to tilt one side or the other.

Originally Posted by astrnmrtom

Two types of shade you'll encounter, one is shading by what's on your roof, and the other is shading from the environment. The first you have more control over, so work with that one first.

We've been full timing for almost three years now and have camped in a lot of different places, from wide open desert, to completely treed over, and everything in between. My original system had panels on one side, and when we planned our boondocking or camping without power, we'd Google Earth the campgrounds to select the best sites if possible. Now, with panels on both sides, it doesn't matter nearly as much.

I do have an on board generator and a small portable, as backups so I'm good in any conditions.

In the winter, tilt brackets make a significant difference. I have 6 panels in 2s3p configuration with a single controller, and it's worked well.

Unless you camp in the same places, your local environment will vary a lot. If you plan ahead, and use Google Maps satellite view, you can have some control.

I did my own system and decided to use tilt brackets. While I've only used them a handful of times, they are always there should I need.

So, I'm in the group that says do what's best for your physical set-up. You have much less control over your environment so that much less of a factor.

I understand the physical shading, this was more of a thought experiment about the environmental side. My current panels on my current small trailer are on tilt mounts as well. But being only 4-100W panels they are in parallel right now to a single controller. I have see 26A to the batteries in early March with clear skies are 9am with them not tilted.

Most of the time, unless I have been running the air conditioner on the inverter for over 1-1.5 hours and really run down the 400Ah LiFePo4 battery array, the solar I have will recharge my previous afternoon and evening's consumption in 2-4 hours. That includes light A/C use to initially cool the trailer, watching TV, using the microwave, charging laptop/phones/hotspot, and using the water pump, 2-way fridge on LP, fans, lights etc. Even with moderate A/C usage the day prior I will be fully charged by 3pm if I am not using anything but simple 12v stuff. Longer A/C runs or when it's crazy hot I will use the generator.

However I plan on using the new trailer slightly differently and want to maximize solar

[9999]

Be careful with a big solar panel set up. If your planning on two string in parallel then the mc4 connectors can't handle the amount of amps in that configuration. You would need to use multiple solar charge controllers. You can do a internet search for " solar charge controller calculator ". Look at multiple sites but I like the one on, https://www.explorist.life/ under the blog tab. Lots of good info there.

[9999]

Also this isn't my site but they also have other useful calculators for solar install. I hope the link isn't violating any forum rules. I also see the irony of my late reply to the original question but if you are like me and were just looking around this will help you.
I'm currently researching my panel configuration myself using 8 of the rich solar maga 24v 200 watt panels, good luck.