Setting up my solar system

[GravelRider]

I'm in the planning stages of adding solar to my travel trailer.

I currently have a battery bank of two 6V flooded lead acid GC batteries in series that is 215 Ah 12 volts. I am planning on adding two more of the same batteries in series-parallel for a 430 Ah 12 volts (215 Ah usable) battery bank. I then plan to add 800 watts of solar. Right now I'm leaning toward using four of the Renogy 200 watt panels.

I plan to wire in parallel, as from what I've read, if I'll be camping in shaded/partial shaded spots, which I usually do, parallel gives better output in these conditions. However, if the panels have internal diodes, does this make this line of reasoning not applicable?

I'll then combine these at a combiner box. Is a combiner box necessary? Or can I just do a T-branch coupler, assuming the amp rating is high enough? And when run in parallel, am I correct in assuming I'll need a fuse/breaker at each positive cable from each individual panel? And if so, is there a combiner box that also has breakers?

From the combiner box, I believe I also need to have a properly rated breaker/fuse to the charge controller, right? And I am planning on a 60 amp MPPT charge controller, that should be correct for 800 watts panels, right?

From the charge controller, I'd need a final breaker/fuse between the controller and the battery, right?

And I'd be using proper gauged wire, based on run length and amperage at each station, probably 10 ga --> 4 ga --> 6 ga. I'd have to measure distances and consult an ampacity chart.

I'm planning on putting the charge controller in the front underneath storage compartment of my Grey Wolf 22MKSE, as this is the closest covered compartment to the batteries. I'm thinking actual line length would be about 5-7 feet from the charge controller to the battery. I don't know where the best place to put the combiner box. I'm thinking having it right next to the controller would be best, in order to cut down line length.

I'm pretty comfortable with electrical in general, but this will be my first go at solar, so please critique my plans and add any advice, it will be appreciated.

Thanks!

EDIT: I should add that the trailer came with a factory installed 50 watt panel with a piddly charge controller. I'll be completely removing this from the system entirely.

EDIT AGAIN: Oh, and what do I do about the AC-DC converter. Will the solar charge controller work seamlessly with this?

And I don't need an inverter at this time. The only thing I really need that is AC when I'm not plugged in is the air conditioning, which I would only use if I had shore or a generator

[GravelRider]

bpounds wrote:

GravelRider wrote:

bpounds wrote:
I had mixed results using a stud finder, but a neodymium magnet found them easily and reliably. This was a trussed roof with rubber overlayment.

Unfortunately mine is stick framed. As far as I know there are no metal roof beams that I'm aware of. Grey Wolf 22MKSE

Mine is wood frame roof too. Truss refers to wood construction. The magnet finds the staples or screws that secure the sheathing to the trusses (rafters if you prefer).

Ah, I see. Good idea on the magnets. I'll definitely use that if my stud finder isn't much help.

[bpounds]

GravelRider wrote:

bpounds wrote:
I had mixed results using a stud finder, but a neodymium magnet found them easily and reliably. This was a trussed roof with rubber overlayment.

Unfortunately mine is stick framed. As far as I know there are no metal roof beams that I'm aware of. Grey Wolf 22MKSE

Mine is wood frame roof too. Truss refers to wood construction. The magnet finds the staples or screws that secure the sheathing to the trusses (rafters if you prefer).

[GravelRider]

bpounds wrote:

GravelRider wrote:

I've got a 96" x 115" area forward of the air conditioner...

Wow, I never would have guessed that. Never seen that much non-penetrated space. Two of those panels will be sweet.

I was actually surprised too when I went up to measure, as it's not a large trailer. Though it's also pretty basic, so not too much stuff up there to take up space. However, in that 96x115" space, there is the stock 50 watt solar panel that I will have to remove. I'm planning to just remove the panel from the mounts and leave the mounts in place. Or maybe it would be better to remove them as well and use generous amounts of lap sealant and/or eternabond tape?

[GravelRider]

bpounds wrote:
I had mixed results using a stud finder, but a neodymium magnet found them easily and reliably. This was a trussed roof with rubber overlayment.

Unfortunately mine is stick framed. As far as I know there are no metal roof beams that I'm aware of. Grey Wolf 22MKSE

[CA_Traveler]

Panel size didn't line up with the beams and I didn't use the 4' beams initially.

The roof is peaked and the beams are flat on 4' centers. Removing some ceiling items like lights determined one location. I drilled a small hole next to one from inside to determine it's exact center location from the roof. From the roof for other beams I drilled a small hole and used a small wire to confirm. I used 3" screws to secure the al angle.

[bpounds]

GravelRider wrote:

I've got a 96" x 115" area forward of the air conditioner...

Wow, I never would have guessed that. Never seen that much non-penetrated space. Two of those panels will be sweet.

[bpounds]

I had mixed results using a stud finder, but a neodymium magnet found them easily and reliably. This was a trussed roof with rubber overlayment.

[GravelRider]

CA Traveler wrote:
That's a good price. I paid $200 for 250W a few years ago and todays prices are half.

That's good to hear. That was better than anything I could find, after figuring in shipping especially, other than some used poly panels on Craigslist. They were selling for $105 OBO per 265 watt panel, and he had about 40 of them available. I was seriously considering that, but the dimensions didn't work for my RV roof. These 400 W panels are perfect.

[GravelRider]

CA Traveler wrote:

GravelRider wrote:
How many mounts should I use on a panel this big (80" x 40")?

4 mounts for the panels themselves. You need to determine what is adequate for your roof.

I used 4 for my 60 cell panels (slightly smaller) which should have been adequate and in fact drove many miles with the 4. However as a result of the install I had a way to pull up on the roof and discovered that in the center it was not attached to anything. Later I installed 4' al angle and long screws to reach the flat ceiling cross beams and added 2 more panel mounts.

Did you have any issues finding the beams with a stud finder? Was the issue on your install that the screws weren't long enough to reach the studs? Or that they were not installed over the studs?

[CA_Traveler]

That's a good price. I paid $200 for 250W a few years ago and todays prices are half.

[CA_Traveler]

GravelRider wrote:
How many mounts should I use on a panel this big (80" x 40")?

4 mounts for the panels themselves. You need to determine what is adequate for your roof.

I used 4 for my 60 cell panels (slightly smaller) which should have been adequate and in fact drove many miles with the 4. However as a result of the install I had a way to pull up on the roof and discovered that in the center it was not attached to anything. Later I installed 4' al angle and long screws to reach the flat ceiling cross beams and added 2 more panel mounts.

[GravelRider]

I called a local solar installation business, and they will sell me two 400 watt panels for $500 total out-the-door for both panels. Sounds like a great deal to me and I won't have to deal with shipping.

These panels:
https://www.solarelectricsupply.com/q-cells-q-peak-duo-l-g7-2-400w-solar-panel

I've got a 96" x 115" area forward of the air conditioner, and with them being about 80" tall, I'll be able to keep them nearly 3 feet away from the A/C unit, thus minimizing shadows from that. I'll have about a maximum of 16" of space between the panels to walk if need be. It'll be tight, but doable.

Also with just the two panels, I can cut way down on wire/connector/breaker costs.

I think I'll pull the trigger on the panels and start shopping for the MPPT controller next.

How many mounts should I use on a panel this big (80" x 40")?

[BFL13]

Over-panelling a little is a good idea with MPPT as Morningstar recommends. NOT with PWM!

You can add to a maxed- out controller by using a second controller for the added panel and parallel the two controllers. I have three from putting solar sets on this Class C from previous RVs.

A 275W with an Eco-Worthy 20a MPPT,
A 255W with a Tracer 20a MPPT, and
A set of three 100W in parallel with a 30a PWM

(The panels are mounted on the roof in a way that they are easy to remove for when I want to change things.)

All three add their amps when set to similar Absorb voltages. The Tracer and the PWM each have a pre-set two hours in Absorb once the battery voltage gets to that, which is perfect for where we are this time of year.

The Eco-W drops to Float as soon as Absorp voltage is reached, but you can set its Float to up to 14.5. But there it stays with no time limit, so you have to crank that down or it stays there after the other two have dropped to 13.6.

The trick is to get the second controller to be compatible with the first so you don't have to monkey with it all so much.

When/if I steal a set to put on the TC, it will be the 275 and Eco-W, because the other two controllers play better together with that set two hour time their profiles.

[CA_Traveler]

Yup, Panel basics 101 teachs us that low sun angles on flat panels yields low power.

The bigger picture: 30V panels are less than half the cost of 12V per watt. A current dealer ad has 295W 60 cell panels for $100 - not a typo. With the more expensive MPPT controllers you still save dollars. Plus you get the shadow benefit especially when they exist for trees or what ever.

If 200W of panels is the goal then sure consider 12V and PWM controller.

There are pros and cons to initial install and upgrades. One pro is earlier solar at less cost. One con is you purchase upgrades that are compatible and likely is not state of the art. That's why I did my research and in 2014 jumped in at 750W. I can't add another serial panel to my controller but could switch to serial/parallel with 4 panels. But I would instead buy 3 295w panels for $300 and sell my existing panels.

So what about my controller that is now over paneled? It's happy and limits to 60A. With 750W my max was 53A, pushed hard, clear day, southern latitude at 1:00PM. So losing a few watts at noonish with 885W is not a issue and I gain capacity from sunrise to sunset and especially during the shoulder hours.

[GravelRider]

BFL13 wrote:
I never got the diode section advantage because the darn sun shading was at an angle to the sections and so crossed cells in more than one section.

I never was able to measure the fabled advantage of having the higher voltage MPPT in lower light and shoulder hours. Was all the same to me. Low light means few amps. Who cares if you get twice the amps between getting 1.5 and 3 ?

I did see the Trimetric action when shading hit one parallel panel and not the others so I still got some amps to the battery. But this was late in the day when the shading was because of a low sun and didn't last long anyway till dark so didn't matter. Also by then, batteries were charged so didn't matter.

No shading and swapping series and parallel and MPPT and PWM I got (as seen on Trimetric same sunshine conditions) same amps to the battery so it just didn't matter what I did--same amps!

What did matter was sunshine on the panels where I had them tilted and twirled to be aimed at the sun as it rose and fell and went around laterally at 15 degrees an hour.

With this rig in the same campground site with the panels now flat on the roof, I get the same results only with more panels to make up for not being able to aim them. Actually I now have more panel wattage flat on the roof than I need on the Class C for here in the summer, so I will likely steal a panel and put it on the Truck Camper we got recently.

Yes you can have too much solar. It is always about the scenario. You find out about that by experience. All you can do at first is estimate. Then be prepared to adjust. Or max out your roof and that is what you have for all scenarios. (Probably the best way to go if not on a budget)

I definitely won't be tilting my panels. I'd rather spend twice as much up front and not have to climb up and adjust them as the sun moves. Plus, if I'm out hiking or exploring in the truck, etc. I don't have to worry about my panels not being adjusted.