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Project complete: 500w solar install, plus 2000w inverter

SJ-Chris
Explorer
Explorer
Project complete: 500w solar install, plus 2000w inverter
(This is on one of my 2015 Thor Majestic 28a RVs)

I wanted to put this together in the hopes that some would find it helpful (...I know I've learned so much from these forums!).

Total cost:
- For the 500w solar:
$225 for the system, and another ~$150 in additional items
~$375 total
- For the 2000w inverter:
$240 for the inverter, and another $100 for cables, outlets, etc
~$340

Total time: ~20 hours

I finally had some free time to tackle this project...adding 500w of solar and a 2000w inverter. Happy to report that things seem to be working well. Here's what I did...

First, I wanted to start with a "clean canvas" (aka: roof). I had notice my Dicor caulking around my front/rear and also around the vents looked like it was starting to crack. I happened to have several gallons of Dicor roof sealant (step 1 and 2) from a previous RV I never got around to sealing, so I thought I'd start by resealing the roof. Here is a link to that project:

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/30201452.cfm

With a clean canvas, it was time to start...

Background: My initial plan was to add 200-250w of solar on the roof, just to provide some modest boondocking capability. My RV has two 100AH Lead Acid (deep cycle) batteries (will be adding a 3rd battery soon). I also have a 4000w generator, but I hate running it while camping (โ€ฆkills the peacefulness of the great outdoors). It is never my intention though to have a serious (large) battery bank and "live off the grid" for extended periods of time. I happened to be visiting Phoenix Arizona late last year and I had stumbled across SanTan Solar (www.SanTanSolar.com) (located in Gilbert, Az 10 minutes away) who sells used residential solar panels and all the components to make an RV solar setup. I had planned on buying a 250w system from them which included one 250w panel, an MPPT charge controller, fuse and a breaker, mounting hardware, and all the wiring (for $165). Seemed like a great price. Well, when I arrived I was surprised to see they were having a sale on their 250w panels and they were just $35 each(!). These are only 10 year old panels and I tested each of them. Soooo, I decided to bump my solar system up to 500w "just because". I was out the door with a complete 500w system with all the components for just $225 (two 250w panels required a bigger MPPT controller and one extra inline 15a fuse).

Here is a before picture of my roof:

On top of the AC is a disabled solar trickle charger that I will remove.

Advanced tip: Before I got started, I tested the entire system on the ground. Layed the two panels on the ground, connected the charge controller to the batteries, then connected the panels to the charge controller. Yepโ€ฆeverything seemed to work. I even did a test where I drained my batteries by ~80AH over night to see if the solar setup would properly do its thing. The test showed me that everything worked as planned. (I certainly didnโ€™t want to attach some panels to the roof with tape and holes/screws, etc only to find out that the system wasnโ€™t working). If you are doing a solar install, I would suggest you do the same.

I then started by mounting the two panels near the front of the RV. I wanted to make sure I had a pathway to walk between them. I also wanted them to be as far as reasonable from the AC to reduce any possible shading impact. My plan was to use five Z-bracketsโ€ฆ.Two on each side and one on the lead edge (front). I wanted to do everything possible to avoid these tearing off the roof while driving down the freeway at 65mph into a strong headwind. I used 3M VHB Tape between the bracket and the panel and between the bracket and the roof surface. For those who havenโ€™t used 3M VHB tape beforeโ€ฆ.it is STRONG. Since my roof is EPDM, I also bolted the brackets to the panel frame and bolted the brackets to the roof surface. Even though the VHB tape is strong, I would never trust it completely on its own (especially on an EPDM roof).

When I drilled the pilot holes for the brackets into the roof, I was a little surprised by how thin the plywood is. I can easily walk on my roof and it feels quite solid, so I thought it would be at least ยผโ€ plywood, but honestly I think it is less. When I screwed the panels to the roof itself, I felt โ€œokayโ€ about the strength, but not great. I always try to think safety first, and I usually decide to overkill it rather than risk it. So, now the panels were VHB taped and screwed to the roof and I didnโ€™t want to even attempt to take them off (โ€ฆwhich I guess is a good sign that they were actually on there pretty good in the first place). So I bought some simple โ€œLโ€ brackets from Home Depot and I added 2 more brackets on the front leading edge and one on the rear edge. So in total, each panel has 8 brackets (16 screws total holding them down). Those panels seem like they are not going anywhere now!


I will probably hit them with another layer of Dicor and trim off those lengthy bolts.

Advanced tip for applying Dicor: After the panels were securely fastened to the roof (and once I retested the system to make sure it was properly working) it was time to use Dicor self leveling sealer/caulking. For a moment I wondered, โ€œHow am I going to apply this Dicor BEHIND the Z-brackets (underneath the panel). There is only about 1 inch of clearance between the roof and the panel framing. Then I came up with an ideaโ€ฆ I bought a couple feet of plastic tubing (Like this: https://tinyurl.com/tubing4dicor) and a small hose clamp. Then I cut off a ~1 foot piece and fastened it to the end of the Dicor tube. Because this tubing comes wound up, it naturally has a curved bend to it. A one foot piece gave approximately a 180 degree bend. This made it simple for me to apply a healthy amount of Dicor BEHIND the bracket exactly where I wanted/needed to. ๐Ÿ™‚

I wanted to keep all the wires very neat and tidy. So I used zip tie mounts in several places and zip ties. To keep the wires tidy underneath the panel itself (and not flapping around), hereโ€™s what I did:


I made sure I left a little bit of wire โ€œslackโ€ where the connections were made joining the two panels just in case I need to replace a fuse or possibly add another panel in the future (unlikely). Here is what the panels look like installed:


(I later Dicorโ€™ed over the wire on the right coming from the panels down the right side of that picture).



When I put solar onto my other RV I plan on hitting this wire with another round of Dicor.

Because I am fairly certain I will never add more solar panels to this roof, I went with 10AWG wire. It is large enough to handle the ~16 max amps these panels could generate. Iโ€™ve got a ~40โ€™ run to my solar charge controller, but 10AWG wire can do that with about a 3.5% drop in voltage. Rememberโ€ฆI only really needed 200-250w, so I didnโ€™t need to worry about this relatively minor drop. I ran the wires down my refrigerator vent which was pretty convenient. During the stretch where the wire is running behind the refrigerator, I put it in electrical conduit and fixed it in place away from any hot components of the refrigerator cooling unit. From there, the wires went through the floor and popped out underneath the RV where I could route the wires (in flex conduit, wrapped in electrical tape) forward and to the driverโ€™s side of the RV underneath the dinette seat. Zip-tied the wiring securely along the way. Under the driver side dinetteโ€ฆthatโ€™s where I put the solar charge controller and my 2000w inverter.

Side note: If you havenโ€™t done this before, I highly recommend you grab 10-20 strong zip ties and you crawl all around underneath your RV. You will likely find PLENTY of wires you can secure better running all over underneath your RV.

From my 2000w inverter, I ran a parallel set (two positive/two negative) of 2/0 cables (~8โ€™ long) to my battery connections (Iโ€™ll be adding a 3rd coach battery in the next couple of weeks). This should handle the large potential current draw from my batteries under the possible heavy load of the inverter. My inverter is mounted right next to my solar charge controller. From my solar charge controller, I have a ~2โ€™ 6AWG wire (thickest that will fit in the solar charge controller) going to my inverter Pos/Neg posts (hence my batteries) with a resettable fuse in between (in case I want to disable the solar at any point while doing other work on the RV, etc). This makes my voltage drop between my solar controller and batteries pretty much negligible.

From my inverter, I created three 120v outlets (two near the dinette, and one all the way back in the bedroom). For the rear bedroom outlet, I used 14/2 outdoor Romex and put it in flexible conduit and routed it mostly underneath the RV fastening it with plenty of other wires running under there. Here is a picture of the outlet added at the dinette.


Here is my Aili battery monitor I installed previously. It now shows me that my 500w of solar constantly keeps my batteries at 100% :C If you donโ€™t have a battery monitor, you should get one. It is the easiest way to know at all times what is happening with your batteries/solar/charging/etc. Very handy, and this one only costs ~$45.


For the places where I was going to be routing several wires (primarily under/through my dinetteโ€ฆSolar wires from the panels, 2 sets of thick cables from my inverter to the batteries, one wire in conduit to the rear bedroom outlet from inverter) I had to drill a sizable hole through the floor and out the bottom of the RV. I found that if I use a 1 5/8โ€ drill bit it makes a nice size hole and then I use one of these 1-1/2 in. x 6 in. White Plastic Flanged Strainer Sink Drain Tailpiece Extension Tubes (https://www.homedepot.com/p/Everbilt-1-1-2-in-x-6-in-White-Plastic-Flanged-Strainer-Sink-Drain-Tailpiece-Extension-Tube-C9800/205154040) cut so that it sticks out about an inch out the bottom of the RV. I could glue this in place and it provides for a smooth exit out of the bottom of the RV (instead of rubbing on the metal undercoating that was drilled through. Once all the wires were done and the system was complete, I stuffed some steel wool inside this tubing so that it was about halfway between the floor and the bottom of the RV, and then I filled the rest (top and bottom) with some sealant foam (like this: https://www.homedepot.com/p/Loctite-TITE-FOAM-Window-and-Door-12-Fl-oz-Insulating-Spray-Foam-Sealant-2260115/302135916?ITC=AUC-62427-23-12140). This sealing (and steel wool) should make it rodent proof and air-tight.

Here is a fairly complete list of components:
- Two 250w residential panels (https://store.santansolar.com/product/santan-solar-t-series-250w/)
- Two 15amp inline MC4 fuses (Amazon.com: Renogy 15A Male and Female Connector Waterproof in-Line Fuse Holder w/Fuse, Black: Garden & Outdoor)
- One Y-branch MC4 parallel wire connector
- 40โ€™ of 10AWG wire with MC4 connector ends
- Two 6โ€x16โ€ screens from Home Depot to re-cover the refrigerator screen that I cut to gain access to drop the wires without having to pull the refrigerator (Gibraltar Building Products 14 in. x 6 in. Galvanized Steel 2-Way Reversible Vent-TW146-1/8 - The Home Depot)
- 5โ€™ of electrical conduit to run behind the refrigerator to keep the wires away from the hot components of the cooling unit of the refrigerator
- Zip tie mounts and zip ties to keep the wires tidy along the way (https://www.amazon.com/gp/product/B07M69LTLJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
- 20โ€™ of 2/0 cables to cut and double up and run two pairs from inverter to batteries (https://www.amazon.com/gp/product/B07FZWBKNZ/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1)
- Bag of copper lug connectors for making custom length cables (https://www.amazon.com/gp/product/B08R6TX3XM/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1)
- Crimper tool for making custom length cables (https://www.amazon.com/gp/product/B07V6V7XZC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
- 5 tubes of Dicor self-leveling sealer
- 1โ€™ plastic tubing and a small hose clamp (to apply Dicor BEHIND the Z-brackets)
- Two 1-1/2 in. x 6 in. White Plastic Flanged Strainer Sink Drain Tailpiece Extension Tubes
- Steel wool and foam sealant (to seal up any openings made in the bottom of the RV)
- Romex, 3 junction boxes and outlet receptacles and cover plates.
- Plenty of electrical tape
- 30 amp MPPT solar controller (https://store.santansolar.com/product/epever-3210-30a-mppt-solar-charge-controller/)
- 2000w Pure Sine Wave Inverter
- Two 40amp resettable fusesโ€ฆone between solar panels and the controller, and one between the solar controller and the batteries. These are located right next to the solar controller so I can effectively enable/disable the solar anytime I need (https://www.amazon.com/gp/product/B07KF2PV6V/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 )
- Misc: Screws, washers, nuts, bolts

I didnโ€™t really keep track of how many hours this project took me. Probably ~20 hours, which included lots of trips back and forth to Home Depot for misc items. I had fun (mostly) doing it, and learned a lot. The good news is that Iโ€™m putting another 400w solar system on my nearly identical Majestic 28a. While I was performing this current 500w install, I bought double the supplies/parts knowing that I have another one to do. I suspect Iโ€™ll be able to install the next solar system on my other RV in probably half the time now that I know all the tricks (and have all the components on hand). This was my first solar project and Iโ€™m very happy with the results. Canโ€™t wait to head off-grid somewhere soon!

Happy Camping all!
Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs
20 REPLIES 20

StirCrazy
Nomad III
Nomad III
SJ-Chris wrote:
1.5yr Update, Test:


One Question: Is it reasonable to be getting 25-26v from my solar panels? Here is the spec sheet:

Maximum Power: 250w
Open circuit Voltage: 37.6v
Voltage at Pmax: 30.3v
Short Circuit Current: 8.85a
Current at Pmax: 8.27a

Regarding Voltage as seen at my solar charge controller:
The wire run from my panels to my solar charge controller is about 35' and is 10AWG wire. Using an online voltage drop calculator with 35', 10AWG, 30v, and 16amps, it says my voltage drop should be 1.3v (4.4% loss, which seems fine to me). Do you think I am not seeing closer to 28v at my solar charge controller because the sun is not directly overhead? Just curious.

As mentioned in my original post, I only really needed/wanted 200w of solar but ended up putting up 500w (because it was so inexpensive with used panels). I'm not trying to squeeze more charging out of my system as it is overkill for my needs already. I just find it fun to tinker around with it. Solar is fun and addictive!

Happy Camping!
Chris


if we were talking a new system I would expect higher, but seeing as you started with 10 year old panels it seams reasonable, maybe it just wasn't as good of a solar day out side also.. if it is meeting your needs then all is good.
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

pianotuna
Nomad II
Nomad II
SJ,

Thanks for the report!
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

SJ-Chris
Explorer
Explorer
1.5yr Update, Test:

I haven't had to do a single thing to my solar or batteries (except check occasionally for water level on the lead acid batteries). The batteries are kept charged and when boondocking I've never even gotten below 50% on my 200AH battery bank.

Just for fun, and out of curiosity, I decided to do a charge test with my solar/batteries. Yesterday evening I ran a small 120v heater through my inverter to discharge my batteries down to 35% (65AH remaining out of 200AH). I disconnected my solar panels (via convenient breaker) and I let the batteries sit overnight. Today at noon I went to my RV and turned on my solar to see what sort of amps I could get flowing into my batteries. There were two reasons I wanted to do this. First, I wanted to see what the maximum solar amps I would get out of my flat mounted panels flowing into my batteries, and secondly I wanted to check the impact of having DIRTY solar panels (I haven't cleaned them ever...only time they get clean is when it rains).

Here was my test...

Conditions: August 12th, 12:45pm in the afternoon. Bay Area, CA. Sunny, cloudless, 80 degrees. Sun high in the sky but definitely NOT directly overhead. Flat roof mounted panels (two 250w residential panels). Battery at 35% SOC (65% discharged). 30amp MPPT solar charge controller.

This is how dirty they both were:


Here is an image of the dirty vs clean panels:


Before cleaning panels:
25v from panel (measured via solar charge controller)
12.0amp from panel(measured via solar charge controller)
23.6 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v

After 1 panel clean:
25v from panel (measured via solar charge controller)
13.3amp from panel (measured via solar charge controller)
25.2 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v

After both panels clean:
26v from panel (measured via solar charge controller)
13.9amp from panel (measured via solar charge controller)
27.3 amp into batteries (measured by Aili battery monitor)
Battery voltage via Aili monitor: 12.7v

Conclusions:
- 27.3 amps out of a 500w solar system seems quite reasonable to me. Thoughts?
- The difference between clean panels and dirty panels was 3.7amps (15.7% improvement).
- My EPEVER 3210 30A MPPT Solar Charge Controller seems to be doing a good job converting extra voltage from the panels into current to the batteries without much loss.

One Question: Is it reasonable to be getting 25-26v from my solar panels? Here is the spec sheet:

Maximum Power: 250w
Open circuit Voltage: 37.6v
Voltage at Pmax: 30.3v
Short Circuit Current: 8.85a
Current at Pmax: 8.27a

Regarding Voltage as seen at my solar charge controller:
The wire run from my panels to my solar charge controller is about 35' and is 10AWG wire. Using an online voltage drop calculator with 35', 10AWG, 30v, and 16amps, it says my voltage drop should be 1.3v (4.4% loss, which seems fine to me). Do you think I am not seeing closer to 28v at my solar charge controller because the sun is not directly overhead? Just curious.

As mentioned in my original post, I only really needed/wanted 200w of solar but ended up putting up 500w (because it was so inexpensive with used panels). I'm not trying to squeeze more charging out of my system as it is overkill for my needs already. I just find it fun to tinker around with it. Solar is fun and addictive!

Happy Camping!
Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

StirCrazy
Nomad III
Nomad III
ya even with two 6V I find a microwave is so so, in the 5th wheel I have four 6V and it is fine.

one thing by going to series with a MPPT controler you will get charging eailer and laiter during the day as the voltage his high enough to start charging. it will be a small curent but an extra couple AH before and after is nothing to complain about. I like your idea about adding two more and going to 1000watts.

Steve
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

SJ-Chris
Explorer
Explorer
Well, at the time when I was buying, I was only looking to buy 1 panel at 250w. Since they were so cheap, I bumped up my system to 500w. At that time, I wasn't even planning on putting solar on my other RV, but I figured, "At this price, I'd better just buy it" and so I did. I have since installed it on one of my other RVs (another identical 500w system).

I will likely add a 3rd lead acid battery giving me 300AH. I think the 500w of total solar power I have will be more than enough to keep them charged. I don't really boondock too much, so I don't really even feel like I need 300AH worth of batteries. But I do have a 2000w pure sine wave inverter and I want to be able to run the microwave from it. I believe it will pull ~150amps at 12v which is too much for just 2 lead acid batteries but I hope 3 will be able to handle the draw.

You can look on craigslist or FB marketplace and find great deals on used solar panels for cheap. Just test them prior to buying. That makes for some very inexpensive solar systems. I think the panels will outlive the duration that most will be holding onto their RVs.

Happy Camping!
-Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

StirCrazy
Nomad III
Nomad III
SJ-Chris wrote:
Well, when I arrived I was surprised to see they were having a sale on their 250w panels and they were just $35 each(!).

Chris


wow, at that price I hope you have two more sitting around to put on when you get more batteries ๐Ÿ˜‰

Steve
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

EMD360
Explorer
Explorer
Thanks for the specific information. I have a 250 watt used solar panel but itโ€™s rather large for the RV roof. Iโ€™m looking at buying newer smaller panels for about $200 each. Iโ€™m very hesitant to drill the hikes in the fiberglass roof though. I read about 3m tape and have used it for other tasks but you are right I would not really want to rely on it alone. Iโ€™ve been wondering if I can attach a framework to the vents like the lids attach. Still working on that plan.
I added batteries to the dinette bench in my previous RV and used the same plastic pipe with steel wool and sealing foam to close it. I havenโ€™t wrapped my new wires yet but I did zip tie several original wires when I was installing a new charger and inverter.
2018 Minnie Winnie 25b New to us 3/2021
Former Rental Owners Club #137
2003 Itasca Spirit 22e 2009-2021

SJ-Chris
Explorer
Explorer
pianotuna wrote:
So how is the system working?


Update: I've been boondocking 3-4 times with this RV (200AH lead acid batteries and 500w of solar installed) each time for 3-4 days. The most strain on the batteries was a trip where I was camping in 35-40 degree F nighttime weather and running the furnace at night. Plenty of TV time and computer use also. I think the lowest I saw the battery bank in the morning was in the high 60s (60% batteries full). As soon as the sun came up the solar kicked in and within a few hours I was up to 85-90% and always up to about 95% by sundown. As you know, the last ~5% charge on your battery tends to take a very long time with lead acid batteries (...they only seem to allow about 1-2 amps in at a time even if your system can deliver 20-30).

All-in-all, I haven't had to worry at all about my batteries at all with my newly installed 500w solar system. I ended up adding an identical 500w system onto my other Majestic 28a. The last battery related project I need/want to do is to add one more 100AH lead acid battery to one of my RVs. This will give me 300AH, but more importantly I believe I'll be able to run my microwave through my 2000w inverter with 3 batteries. (With just 2 lead acid batteries the amp draw through each will be about 80amps which I'm not comfortable with. With 3 batteries it drops down to ~50amps from each battery which I think is manageable for a few minute microwave task.)

Happy Camping!
Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

pianotuna
Nomad II
Nomad II
So how is the system working?
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Xander
Explorer
Explorer
You're definitely doing great, but I think you could install solar cheaper if you did a better search on the Internet. And now prices are actively falling on this. So I would recommend people to watch https://www.renogy.com/iot-monitoring/. On this site, there is more up-to-date information that will help with the installation of solar panels.

SJ-Chris
Explorer
Explorer
John&Joey wrote:
What was the logic for running so much wire on top of the roof vs plunging inside?


Has mostly to do with ease of installation (....and/or the fear of the unknown!). I don't really know much about how the roof and walls of the RV are designed and what space is in between and how easy/hard it is to route wires "invisibly" in the walls/ceiling. Because I knew I could do it, I routed the wires from the panel and shot them down the refrigerator vent.



And then punched through the bottom of the RV and routed underneath the RV (easy access) over to the driver side dinette.

~10' run on the roof....~10' drop from roof down to the underside of the RV...~15' run from underneath the refrigerator to the driver side dinette...and then about 4' punching back up into the RV under the dinette to the solar charge controller.

According to my calculations, I'm looking at a max of ~3.5% voltage drop (if the panels were at max output of 16 amps). 500w becomes 482.5w. Negligible.

-Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

John_Joey
Explorer
Explorer
What was the logic for running so much wire on top of the roof vs plunging inside?
Thereโ€™s no fool, like an old fool.

2oldman
Explorer
Explorer
SJ-Chris wrote:
.I could run them in series. This would double the voltage and cut the current in half. My voltage drop % would go from ~3.5% down to ~0.86%.
Nice job!

Yes, series cuts the wire size, the voltage loss and the combiner box. It isn't as big a deal with shade as you might think, provided your panels have bypass diodes. Inverters come in higher voltages too.

For your next install you may want to consider being able to tilt the panels. Makes a big difference in winter.
"If I'm wearing long pants, I'm too far north" - 2oldman

time2roll
Explorer II
Explorer II