Classic 345 Motorhome Solar Project.

[Keyair]

Living in the West, it seems logical to get the most out of the sun.
Thought I better start a thread to document the journey into solar, get advice, and share some ideas too.
My game plan is to squeeze as much solar onto the roof, in an efficient, yet esthetic way, whilst keeping cost down by adding more panels as I can.
My aim is 1.5kw.
A tall order, but I just proved it just might be possible.
My solar hot water heater project is coming along, and is documented in the Plumbing/water heater section.

I’ve had a small Unisolar 32w Panel temporary mounted on the front of the roof to keep the House battery charged for a while.


Just completed the white roof paint project, so it was time to get serious.


I’ve been looking around for a while, and really wanted flexible panels, but reliability/cost/mounting issues steered me away. I might well still get some but for now, I focused on framed units.

After looking for ages, I selected the Renogy Compact Mono 100w units. These panels are well made, proven, and very cost effective at about $100 shipped each, so $1/w. But the real killer thing is the size. They are about 42”x19.5x1.3”. That is some 4” narrower than most units.
Specs.

The narrower width was key in my plan. It mean I can get 3x across the 60” roof section, but also, when stowed, they fit real tight against the curve, which I find pleasing to my eye.

[Keyair]

I bought just 3 to start with.
Yesterday, I started the Solar Panel Tetris game!

My Motorhome has 2 AC units, 2 Maxxfans, 2 bathroom vents, 2 waste tank vents, and one refrigerator vent to contend with. I have decided to remove the TV antenna.

Let me state upfront that some of the areas show might have shading issues, which I hope to negate by tilting the panels.

First of all, this is how tight they can fit against the roof curve, when stowed.


First area to test was behind the front AC unit, between it and the front Maxxfan.
3 panels.
300w/15a total.



I ended up moving these 3 further forward tighter against the rear of the AC later.
Then, along the Curbside I think I can squeeze two more going rearward from there.
500w/25a total.



Then one mounted center roof behind the front Maxxfan, and one mounted on the streetside. Can’t get 3 across that width due to the refrigerator vent.
700w/35a total.


Next area is behind the rear AC.
Three panels across the width.
1000w/50a total.

[Keyair]

After that it gets a little tighter, but these are the possibilities.

Either side of the front AC.
Streetside sticks out more than I’d like, and Curbside is tight.
1200w/50a total.



Then two panels in front of front AC.
1400w/70a total.


Then right at the rear, I think 5x 50w Panels aside of and rearward of the rear Maxxfan is possible.
Only have 100w panels, but the 100w units show the space.
1650w/85a total.

[pdavitt]

Steve,

With 1,650W of panels you are on the edge, or have moved beyond, what is practical for a 12V battery system. Those panels are capable of producing 137A @ 12V. The problem is not on the PV side of the Solar Charge Controller, but on the battery output side. You will have to use at least two Charge Controllers since the highest amperage Charge Controllers available are 100A.

The best advice I can give is that you are building a system, not a collection of individual pieces. Design the whole system and make sure that all the components meet your design criteria. It's best to do this on paper before you spend a lot of money. I did the system design below before I bought anything.


Also, have a professional EE review your design. What I show below is only for illustration purposes.


Pat

[Keyair]

Thanks for the input!
I think it important to note about my post above, that it is "Theoretical", to put 1650W on the roof.

Its important for me to build this over time, as funds allow.I have 9 tires to buy before we hit the road this year, and they are more important than Solar!

I have 300w in my hands, and our plan is to buy another 300w in the next couple of months, and maybe be at 900w by the end of the year.
These will be placed in 3 banks of 3, each bank parallel. I think, each with their own PWM controller.

How many Airstream have 900w on the roof?
I know the Airstream Motorhome is a different proposition in some ways, but the roof space is very similar to a 34' trailer, with pretty much the same space limitations.
My approach, and ideas might make someone else look at the available space they have, and see a solution.


I forgot to mention that I have modified my battery tray, and it now can physically accept up to 8x 6v Golf cart batteries. I only have 2 currently, asand they are 7 years old, but still doing ok. The weight is the bigger issue. I have identified another area that could accept another 4x 6v's, if I want.

It may well be that I end up going Lithium later, but for now, this will suffice.
My idea is to build each panel, or group of panels with a tilt mount that can be angled up from either side. I have the design on paper, and am collecting materials now to fabricate them.

[pdavitt]

Originally Posted by Keyair

Thanks for the input!
I think it important to note about my post above, that it is "Theoretical", to put 1650W on the roof.

Its important for me to build this over time, as funds allow.I have 9 tires to buy before we hit the road this year, and they are more important than Solar!

I have 300w in my hands, and our plan is to buy another 300w in the next couple of months, and maybe be at 900w by the end of the year.
These will be placed in 3 banks of 3, each bank parallel. I think, each with their own PWM controller.

How many Airstream have 900w on the roof?
I know the Airstream Motorhome is a different proposition in some ways, but the roof space is very similar to a 34' trailer, with pretty much the same space limitations.
My approach, and ideas might make someone else look at the available space they have, and see a solution.


I forgot to mention that I have modified my battery tray, and it now can physically accept up to 8x 6v Golf cart batteries. I only have 2 currently, asand they are 7 years old, but still doing ok. The weight is the bigger issue. I have identified another area that could accept another 4x 6v's, if I want.

It may well be that I end up going Lithium later, but for now, this will suffice.
My idea is to build each panel, or group of panels with a tilt mount that can be angled up from either side. I have the design on paper, and am collecting materials now to fabricate them.

It doesn't matter if you will build the project in stages or all at once. You still need to design the project to your final goal. On the project I showed you above I spent about 80% of the total project time researching and designing. After that, actually building the project was the easiest part. You might want to talk to the folks at AM Solar, they are very helpful to DIYers and have many years of experience installing solar systems on RV's.

For a potentially high wattage panel array I would not recommend PWM controllers. You will be much better off with MPPT controllers.

Pat

[TouringDan]

I want to tag along on this thread as I have a 34’ that I plan to install solar on.

Dan

[Isuzusweet]

You'll understand if I'm only keeping my PITA status alive here with this comment.

What effect will aerodynamics play a role in the lifespan of these panels? If they are to be un-stowed when camping, what is stopping them from becoming un-stowed when moving? What is the lifespan of the bracket, or fastener, holding them on if subjected to miles of wind, turbulence and vibration.

The reason I ask, is that, one day I had an awning almost completely unravel itself from the side of my motorhome due to a wind gust while I was doing over 50mph. To say I was shocked that it could open up the awning cover and pull out the awning that fast is an understatement; but it did. There I was, in a ditch at the side of the road having to unlock the awning legs, pull the awning completely out and retract it.............all in high wind conditions.

Cheers
Sidekick Tony

[Keyair]

Welcome onboard Dan!
Lets hope we all learn something from my rambling!


Dang it Tony... I can't escape you even up here...


The plan is...

2"x 1/4"(50mmx 6mm) L bracket aluminium(See, Im Bi Lingual), in 4"(100mm) lengths, screwed/Riveted to the roof. Dependent on the group, the array will be individually mounted, and tllted, or in 2's or 3's. The frame for group panel tilts will be 2"x1/4" thick L or strip, TiG welded where needed.

Panels will be bolted to brackets during travel, by the normal method everyone uses. Tilt will be handled by removable legs of said 2"x 1/4" stock.
My understanding is that the annual tilt variation is from 10deg in summer to 50 deg in winter for ideal inclination... so that means 10" to 50" of leg....

[Keyair]

Here is my Baby...

[TouringDan]

Originally Posted by pdavitt

Steve,

With 1,650W of panels you are on the edge, or have moved beyond, what is practical for a 12V battery system. Those panels are capable of producing 137A @ 12V. The problem is not on the PV side of the Solar Charge Controller, but on the battery output side. You will have to use at least two Charge Controllers since the highest amperage Charge Controllers available are 100A.

Pat

Pat

Victron specifies that their MPPT 150/100 SC is good for up to 1,450 watts. If you install this on a system with 1,650 watts of solar panels, won’t this work fine for at least 95% of the time?

Dan

[pdavitt]

Originally Posted by TouringDan

Pat

Victron specifies that their MPPT 150/100 SC is good for up to 1,450 watts. If you install this on a system with 1,650 watts of solar panels, won’t this work fine for at least 95% of the time?

Dan

Dan,

It's not just the panel wattage, it's the entire system. The OP stated that he was going to have around eight 6V GC batteries. Assuming they are 100AH batteries, that's 400A charge/discharge current at a 1C rate for a 12V system. Also, there is a reason why Victron and other manufacturers do not offer 12V inverter/chargers above 3000VA; they are not practical. What I am trying to say is that changing the system battery voltage to 24V just makes the system wiring and circuit protection devices smaller, simplifies the system, and makes it more flexible.

It's no big deal to add a 24VDC to 12VDC converter to handle the 12VDC loads. And, with that much solar on the roof, you don't have to worry about charging from the TV's alternator.

Pat

[Keyair]

Batteries I plan to use are Interstate 6v GC 105, and rated at 210ah @20hr.

The charge controller/controllers I am looking at are the Renogy Rover 40a MPPT.

[Keyair]

Got some 2” L extrusion for the solar frames.


Cut to 61” lengths for now.
Into the English wheel they went to be curved to match the roof.


I will have to confirm I have the correct curve next week with a test fit. It might need some more.


Test fit with the panels.
There will be 3x 100w panels in each frame, across the roof bow. They will be able to tilt up as an assembly.
Attachment 1

Planning to use this thicker L for the roof mounts.

[fireleu6169]

Steve, what are the issues with flexible panels. I am new to this stuff and wife wants flexible panels

[Keyair]

Quick update.
Frame is progressing and looking promising.
Hope to get out and find some 2x2 x 1/8” T extrusion to go between the panels and strengthen the frame.


Further to my previous posts, I’m pretty sure I’m going to
24 or 48 volt LifeP04 batteries.