Large Residential Solar Panel

[Watsons]

Hi all, has anyone used the larger residential (6' x 3') panels with success?
There seems to be benifits to these one being the price per watt is better than the smaller (RV) ones. Looking at a 335 watt for $260 CAD
Just concerned the large flat glass may crack when flexing on bumpy roads etc.
Thoughts? Experiences?
Cheers

[Shackrat]

I wouldn't want something that large on the roof, it's a huge sail that's going to be heavy to left on the roof and expensive to replace if damaged.

I would go smaller if it were me. There will be less lift from air passing underneath, and if something does damage them you'll not have such a huge cost. Plus the smaller panels allow you to place them in tight areas around other things on the roof. Also keep in mind you still need to walk on the roof too!

I thought mine were huge at 58"x26".. I cannot imagine going any bigger!
Those are US$180 per panel with each panel being 195W peak. Two panels would be roughly 3,000 square inches. Your large panel is 2600 square inches.

That works out to 0.130W/sq inch for my panels and 0.128W/sq in for yours. So in this case the smaller panels actually have a slightly higher power density too.

[Watsons]

Originally Posted by Shackrat

I wouldn't want something that large on the roof, it's a huge sail that's going to be heavy to left on the roof and expensive to replace if damaged.

I would go smaller if it were me. There will be less lift from air passing underneath, and if something does damage them you'll not have such a huge cost. Plus the smaller panels allow you to place them in tight areas around other things on the roof. Also keep in mind you still need to walk on the roof too!

I thought mine were huge at 58"x26".. I cannot imagine going any bigger!
Those are US$180 per panel with each panel being 195W peak. Two panels would be roughly 3,000 square inches. Your large panel is 2600 square inches.

That works out to 0.130W/sq inch for my panels and 0.128W/sq in for yours. So in this case the smaller panels actually have a slightly higher power density too.

Real quick reply..
The research I did pointed at larger quality panels were all round better built and provided more amps to battery through a good MPPT.
There was the cost as well.
Price per watt
Mine was $260CAD/335watts= $0.78/watt CAD
Your two panels at $470CAD/390watts=$1.20/watt CAD
If a large hailstone takes mine out its $260 where if one takes yours out its $235 so pretty much a wash I would say. To add to that this one is a DUO which gives it 2 seperate sections so one can be damaged or in the shade and the other half will put out as usual.
Lots of room to walk around it as well so not a concern
You did mention some valid points about wind etc which I will midigate by securing them well with 6 brackets (vs 8 on yours).
Not hacking you, just adding to the senario and conversation.
Cheers and thanks for replying.

[JimD]

I asked my son, who is an electrician for Tesla solar installs, what the voltage output from a single residential panel is. He said they varied. So, I guess it would all depend on what the panel is capable of and if it is the correct voltage for our application.

I personally have 4-100 watt panels mainly because I originally started with 2 panels. I went with ones designed for an RV which is probably the wisest choice.

[Watsons]

Originally Posted by JimD

I asked my son, who is an electrician for Tesla solar installs, what the voltage output from a single residential panel is. He said they varied. So, I guess it would all depend on what the panel is capable of and if it is the correct voltage for our application.

I personally have 4-100 watt panels mainly because I originally started with 2 panels. I went with ones designed for an RV which is probably the wisest choice.

Well I'm sure no expert in this area but am enjoying the learning opportunity.
Its a 40 volt panel that my solar guys say will charge like crazy through a good MPPT. We will see..
My main goal was less holes in the roof, less wiring and connections, more technically advanced panels and around here availability. The Covid craze has people buying rv's at record levels and slapping the ready made solar kits on them and heading for the hills.
Thought I could put together a top of the line system for less than the kits by piecing it together (which I have accomplished).
I wanted the LG 360 Neon 2 which is nearing top shelf but supply issues with that as well. Settled for a Q-Cell 340 (mistakenly called it a 335 in initial post)
Am still hoping someone else has done the same thing and will comment.
Cheers!

[Shackrat]

Since you're learning…. Allow me to explain how the voltage of a panel has little to do with how effective the panel is for powering an RV.. A higher voltage with less current simply allows for a smaller gauge of wire to be used.

A 12v panel typically runs at 18v (ish) in peak sun. If a panel is rated 200 watts it means it is producing around 11 amps. When you parallel panels you have to sum the current for all panels. I have 4 195w panels, (780w total) with peak current just over 40 amps, which is right at the limit of the 8awg wire. The current capacity (ampacity) of the wire is maxed, but not the overall ability to carry power if I transition to a series/parallel arrangement (more on that later).

A 40v panel that is producing 330 watts is producing about 8 amps peak. More voltage/less current is meaningless when using an MPPT controller. Either is fine.

Back to the series/parallel arrangement. This allows for maximizing the amount of power that can be carried over a wire. In my case, I'm at 41 amps which is the limit for 8awg. But that doesn't mean the wire cannot carry more power.

I could add a second bank of panels in series (assuming all are same voltage) with the first bank. This effectively raises the grid voltage to 36v (actual). Current remains at 41amps but the grid voltage is 36v with a total wattage of 1560w. The MPPT controller is ambivalent since it can handle over 100 volts so long as the current remains at or below 40 amps. Note that theoretically I'm over 40 amp limit of my controller, but since my panels are flat and will never be optimally angled, they'll never reach peak generation.

[Watsons]

Originally Posted by Shackrat

Since you're learning…. Allow me to explain how the voltage of a panel has little to do with how effective the panel is for powering an RV.. A higher voltage with less current simply allows for a smaller gauge of wire to be used.

A 12v panel typically runs at 18v (ish) in peak sun. If a panel is rated 200 watts it means it is producing around 11 amps. When you parallel panels you have to sum the current for all panels. I have 4 195w panels, (780w total) with peak current just over 40 amps, which is right at the limit of the 8awg wire. The current capacity (ampacity) of the wire is maxed, but not the overall ability to carry power if I transition to a series/parallel arrangement (more on that later).

A 40v panel that is producing 330 watts is producing about 8 amps peak. More voltage/less current is meaningless when using an MPPT controller. Either is fine.

Back to the series/parallel arrangement. This allows for maximizing the amount of power that can be carried over a wire. In my case, I'm at 41 amps which is the limit for 8awg. But that doesn't mean the wire cannot carry more power.

I could add a second bank of panels in series (assuming all are same voltage) with the first bank. This effectively raises the grid voltage to 36v (actual). Current remains at 41amps but the grid voltage is 36v with a total wattage of 1560w. The MPPT controller is ambivalent since it can handle over 100 volts so long as the current remains at or below 40 amps. Note that theoretically I'm over 40 amp limit of my controller, but since my panels are flat and will never be optimally angled, they'll never reach peak generation.

Good day shackrat. Thanks for your reply.
Below I have copied a text from my solar guy regarding why I should go with the larger panel.
If you would be so kind as to review and comment, I have till tomorrow morning to cancel out of my deal if it's all hogwash.
Thanks much

" Although a 160W panel puts out ~9A, it is all about the wattage of the panel. Ie the 160W Panel will put out 160w but at 18V x 9A. The LG 350W will put out 350W at 10A x 35V. The MPPT controller does the job of taking that wattage and turning it into whatever battery bank you have...12V or 24V. So for the 350W it will convert that into 350/13.6V= 25.7A to the battery. So over 5 hours that is 128.6ah per day, or 1544wh/day"

[pconroy]

Some possible advantages to going with smaller panels: you might be able to mitigate shading issues easier with smaller panel wiring approaches. Tilting would probably be easier -- if you were planning to tilt.


Then there's installation - I'd rather heft up a 100 watter.


I'd be curious to see if residentials are inherently less susceptible to shading. My guess is that they won't be.

[Watsons]

Originally Posted by pconroy

Some possible advantages to going with smaller panels: you might be able to mitigate shading issues easier with smaller panel wiring approaches. Tilting would probably be easier -- if you were planning to tilt.


Then there's installation - I'd rather heft up a 100 watter.


I'd be curious to see if residentials are inherently less susceptible to shading. My guess is that they won't be.

From what I read, the producers have dedicated more time on the "residentials" in that regard. This one for instance is broken into two separate parts so if one corner gets shade that half degrades output while the other half keeps going. Sort of like having two panels. 🤷*♂️
Installation will be a breeze...less that 50lbs and with two people and two ladders...easy..
Less holes in roof is another plus..
I'm not duking it out just passing on my reasons for choosing this route..right or wrong..

[pconroy]

Originally Posted by Watsons

I'm not duking it out just passing on my reasons for choosing this route..right or wrong..

Me neither - I'm looking at this as a chance to learn.
Will Prowse just posted a video demo'ing the SunTan used panels - $50 for 250 watts.

[Shackrat]

Originally Posted by Watsons

" Although a 160W panel puts out ~9A, it is all about the wattage of the panel. Ie the 160W Panel will put out 160w but at 18V x 9A. The LG 350W will put out 350W at 10A x 35V. The MPPT controller does the job of taking that wattage and turning it into whatever battery bank you have...12V or 24V. So for the 350W it will convert that into 350/13.6V= 25.7A to the battery. So over 5 hours that is 128.6ah per day, or 1544wh/day"

His math checks out so no worries there. If you’re running lithium batteries your system charge voltage is likely 14.4v instead of 13.6 but it is ultimately the watt-hours that matter most. However, his math is also based on the panels being given a southern exposure and tilted at a very specific angle relative to your location. You haven’t talked about how you plan to mount these but unless you’re going to use tilting mounts, which I’ve never seen for a panel that large, your actual generation could be half of what he’s calling for.

And that brings me to ask this. Have you calculated your needs yet? That frankly, is the hardest part. Start with your static loads; fridge, gas detector, slide & leveling controllers, usb chargers, TPS, water heater, etc. On my camper that amounts to a whopping 2.6 amps. I added a second 12V “boondocking” disconnect that kills the leveling and slide controllers & the TPS. But it is still 1.8 amps which over a 24 hour period works out to 43.2 amp-hours. (513.2 watt-hours) That’s almost half of an entire 100AH Lithium battery!

If you go with the 350 watt LG panel, roughly 1/3 of your peak optimal capacity is going to be used maintain your static loads in your camper. And that of course assumes peak efficiency with optimal sun angle, as well as sun exposure (lack of shade and clouds).

Once you have that figured out you’ve got to work out the average of your dynamic loads; lighting, water pump, vent fans, and inverter use to name a few. Those are hard to predict so don’t be surprised if you have to change your usage habits.

[Watsons]

Originally Posted by Shackrat

His math checks out so no worries there. If you’re running lithium batteries your system charge voltage is likely 14.4v instead of 13.6 but it is ultimately the watt-hours that matter most. However, his math is also based on the panels being given a southern exposure and tilted at a very specific angle relative to your location. You haven’t talked about how you plan to mount these but unless you’re going to use tilting mounts, which I’ve never seen for a panel that large, your actual generation could be half of what he’s calling for.

And that brings me to ask this. Have you calculated your needs yet? That frankly, is the hardest part. Start with your static loads; fridge, gas detector, slide & leveling controllers, usb chargers, TPS, water heater, etc. On my camper that amounts to a whopping 2.6 amps. I added a second 12V “boondocking” disconnect that kills the leveling and slide controllers & the TPS. But it is still 1.8 amps which over a 24 hour period works out to 43.2 amp-hours. (513.2 watt-hours) That’s almost half of an entire 100AH Lithium battery!

If you go with the 350 watt LG panel, roughly 1/3 of your peak optimal capacity is going to be used maintain your static loads in your camper. And that of course assumes peak efficiency with optimal sun angle, as well as sun exposure (lack of shade and clouds).

Once you have that figured out you’ve got to work out the average of your dynamic loads; lighting, water pump, vent fans, and inverter use to name a few. Those are hard to predict so don’t be surprised if you have to change your usage habits.

Glad to hear it wasn't smoke and mirrors from the sales fella..
We ended up with a Q.PEAK DUO-G6 340 from Q-Cell module.
Hmm..never concidered the static loads to be that high. Our biggest drain is the furnace fan at 6 amps. It runs about 10 hours at 50% cycle so 5 hours or 30amp hours. Havent added up all our other usage such as led lights, water pump, stereo.
Batteries at this point are 5 year old Canada Proof lead acid at 220ah.
I pretty much just took a stab in the dark and worked within our budget at this point which was in the $700 CAD mark. Concidered our location (Alberta), clouds and rain and came up with what I hope is enough for a 3 or 4 day boondock without having to use the genny to charge..
I realize one can be quite precise in calculating needs but didn't do my part there.
Guess we will see how it turns out and go from there.
Really appreciate your time and comments. Its a steep learning curve.

[Jay2504]

Watsons, although I will never have a Solar set up, I am really enjoying learning from your experience. I like the idea that you are “thinking outside the box” about which panel(s) to use. Please keep us informed on how it works out. We just got back from “boondocking” at the race track. Normally when we go there we just run the generator 24/7 for the AC. This time, we didn’t need AC and ran the furnace at night. Our one old group 31 made it through each night, but we had to run the generator for a few hours each day to charge it back up. Going to upgrade the battery for now. Jay.

[djglover7]

Forum,


Whenever I spot a good thread, I try to read all of it. This is a good one.

I do not have panels but I will eventually. Need to learn more.

Has anyone ever thought of using panels as shade covers for windows?

Built right, made adjustable, and removable, may kill two birds with one stone.

??

[daveobieone]

We had not one, but two big 300 watt panels on the top of our 29.5 5th wheel.

Never had any problems. The big panels require less holes in the roof, and less chances for leaks. They never turned into sails, and never came loose, and never leaked, and never broke. I used 3 L-brackets on each short side of each panel and 4 on the long sides...so each panel had 14 L-brackets holding it down to the roof.

Because of the layout of the roof, one panel was positioned long-ways with the trailer, and one was cross-ways.

In direct sun, the most we got was about 550 watts of output, because they were flat mounted to the roof. That coupled with a 40 amp MPPT charge controller worked really great. On clear mornings, we were nearly fully recharged by about 10am, and on cloudy mornings we were fully charged by noon or so. It was a boondockers dream! Power to burn all day, any day. Movies at night, lights (LED of course), fans, or furnace at night. Never a problem. We could take advantage of the best sites with the best views, and never worried about hook-ups.

We used this set-up for a few years with no problems. We've since sold that trailer to another couple who's still using the solar set-up I put in. When we buy our next RV, which will be a C or A, I'll do exactly the same thing to it.

Dave O.

[ARoamer]

We have 2- 5.5' x 3.3' 320 watt 33v residential panels on out 5th wheel roof. ($200 each new.) They work great with a mmpt controller. Similar performance as daveobieone's, 3-100AH lithiums are recharged by 10 am depending on previous night's use and cloud cover. I am quite happy with this setup so far. Our trailer's "static loads" would drain the original single lead acid in 3-4 days. Now the 110vac breaker for the 12v charger is left off and I let the panels and batteries run all the 12v loads even when connected to shore power.

Check out the social group- RVing with solar. Group Maintained by Mustang65

[Watsons]

Thanks for the info and comfort daveobieone and ARoamer.
Looking forward to installing our 340 watt Q-Cell next weekend.
I am making my own 2 piece brackets 4" long with 1.5" of lift and the ability to take the panel down if ever needed without disturbing the roof mounting screws.
I am thinking 3 brackets down each side and 2 on each end secured to roof with 2 - 1/4" x 1" long stainless lag bolts per bracket. I have the truss schematic from Jayco to help with locating trusses and hopefully hit a couple. (then use longer lags).
I am adding a 3/4" wide x 1.5" long x 1/8" thick backing plate where the bracket bolts to the panel as I read where someones bolts pulled through the aluminum panel frame and he lost his panel.
In the spirit of the forum I will attach a few pics when I get going on the project.
Cheers