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

[SJ-Chris]

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

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. This was my first attempt at installing solar. 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.irv2.com/forums/f87/rv-roof-sealing-project-524232.html

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 (…kills 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. Yep…everything 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 didn’t want to attach some panels to the roof with tape and holes/screws, etc only to find out that the system wasn’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-brackets….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 haven’t used 3M VHB tape before….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 ¼” plywood, but honestly I think it is less. When I screwed the panels to the roof itself, I felt “okay” 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 didn’t want to even attempt to take them off (…which I guess is a good sign that they were actually on there pretty good in the first place). So I bought some simple “L” 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, “How 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 idea… 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. J

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), here’s what I did:




I made sure I left a little bit of wire “slack” 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 Dicor’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. I’ve got a ~40’ run to my solar charge controller, but 10AWG wire can do that with about a 3.5% drop in voltage. Remember…I only really needed 200-250w, so I didn’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 driver’s side of the RV underneath the dinette seat. Zip-tied the wiring securely along the way. Under the driver side dinette…that’s where I put the solar charge controller and my 2000w inverter.

Side note: If you haven’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 (~8’ long) to my battery connections (I’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 ~2’ 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% If you don’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 dinette…Solar 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 5/8” 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...9800/205154040) 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-...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/produc...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
- 40’ of 10AWG wire with MC4 connector ends
- Two 6”x16” 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)
- 5’ 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/B0...?ie=UTF8&psc=1)
- 20’ of 2/0 cables to cut and double up and run two pairs from inverter to batteries (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1)
- Bag of copper lug connectors for making custom length cables (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1)
- Crimper tool for making custom length cables (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1)
- 5 tubes of Dicor self-leveling sealer
- 1’ 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/produc...ge-controller/)
- 2000w Pure Sine Wave Inverter
- Two 40amp resettable fuses…one 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/B0...?ie=UTF8&psc=1 )
- Misc: Screws, washers, nuts, bolts

I didn’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 I’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 I’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 I’m very happy with the results. Can’t wait to head off-grid somewhere soon!

Happy Camping all!
Chris

[astrocamper]

I have been using solar since 2009. The first 8 years I had 240 watts of solar, 1000 watt inverter and a pair of Trojan T105 batteries. The system worked great and I just had to add water every few months. Batteries were in great shape when I sold the 5x8 cargo trailer.

My larger Artic Fox 22G has 1440 watts of solar and a VE Multiplus 3000VA inverter charger and a larger LiFePO4 battery bank. I love the quiet of solar and the ability to not have to worry about running down my batteries. I have power when I need it.

I am sure you will enjoy the solar on your trailer. Since you installed it yourself you can appreciate how much you saved verse contracting it out. Hope you get a lot of years out of it.

[Allen_C]

What is the amp input to your batteries that you receive on a sunny day with this? Are the panels 12v or 24v nominal?

[twinboat]

Originally Posted by Allen_C

What is the amp input to your batteries that you receive on a sunny day with this? Are the panels 12v or 24v nominal?

36 volt nominal.

[SJ-Chris]

Originally Posted by Allen_C

What is the amp input to your batteries that you receive on a sunny day with this? Are the panels 12v or 24v nominal?

The voltage at the solar controller is ~35-36v. The max amp output listed on the panel is 8.2amps (per panel). In theory, there could be 16.4amps flowing from the panels. 36v converted into 13.6v (via the MPPT controller) could in theory multiply the current by 36/13.6 = 2.65.
2.65 x 16.4amps = 43.5 amps max (...in theory).


But we can all agree that a solar system with flat mounted panels and long wire routing and sun position and clouds/shade, various times of the year, etc is far from optimal.


My MPPT solar charge controller is only rated for 30 amps of output. I'd be happy if I ever saw 30 amps actually flowing into the batteries from this solar system at peak sun during summer time. I'll let you know. I certainly think it's possible. Normally, you would NEVER want your solar charge controller to limit the output current...but in my case I didn't care because as I stated I was fine in the beginning with the idea of putting just 200-250w of solar on my RV and now I've got 500w (for cheap).



In March (winter time) with the afternoon sun, I saw 10+ amps flowing from the panels and 20+ amps flowing out of my solar charge controller into my battery bank when I was testing it. I'm confident with summer sun more overhead I'd see numbers getting closer to the 15-16 amp maximum from the panels resulting in maxing out my 30 amp solar controller..



I have also learned more about battery charging and I know now that your batteries will only receive maximum charging amps (whether from solar, or generator, or alternator, or shore power) when the batteries are far from full. Once the (lead acid) batteries get up to about 80%, the battery starts limiting the amount of amps that can flow into them so it doesn't matter if your solar system is generating 2x, 4x, 10x more amps....the batteries will only accept a certain amount.



I'll give an update once I give it a better stress test.


Happy camping!
Chris

[BCam]

Originally Posted by SJ-Chris

I have also learned more about battery charging and I know now that your batteries will only receive maximum charging amps (whether from solar, or generator, or alternator, or shore power) when the batteries are far from full. Once the (lead acid) batteries get up to about 80%, the battery starts limiting the amount of amps that can flow into them so it doesn't matter if your solar system is generating 2x, 4x, 10x more amps....the batteries will only accept a certain amount.
Chris

This should be mentioned more often. So many of us install solar and are then disappointed that we only see 1.5A - 3.0A, or less, going into our batteries when we were expecting 15A, 20A or more. I know I was until I figured it out. The same is true of battery chargers.

[SJ-Chris]

Originally Posted by BCam

This should be mentioned more often. So many of us install solar and are then disappointed that we only see 1.5A - 3.0A, or less, going into our batteries when we were expecting 15A, 20A or more. I know I was until I figured it out. The same is true of battery chargers.

Agreed!


When your battery (lead acid) has been discharged down to 50% or 60% overnight, then when your solar kicks in it will be able to deliver those high amps (depending on how much solar you have). I've seen 20-30 amps which is what I expect.


I have learned to be content with seeing my batteries "Only" charged up to 90-97% each day when I'm boondocking. It just seems like the last ~10% to get to 100% is VERY slow. Especially the last 3-4%.


I also wish more people would understand that it is OK to *occasionally* let your lead acid batteries discharge 70-80% of their total capacity. Everyone is brainwashed with the "Don't go below 50%" mantra. For 99%+ of all RV users, they will NEVER wear out their batteries because of too many charge-discharge cycles. How many days of boondocking does the typical RV owner do each year? 5 days? 20 days? If you did 20 days for 10 years that would be 200 days. If you discharged your battery 80% everyday (...which you likely never would), that would be just 200 cycles of charge-discharge. Not a big deal. I believe most batteries die from getting fully drained 100% and left like that for weeks or months (ie. in storage), and certainly if you let them get 100% drained frequently they are not going to last. The beauty of solar is that every sunny day your batteries are getting charged and/or topped off in storage.


Happy Camping!
Chris

[TexasJeff]

Excellent information. Thank you! I'm still learning about solar so any time someone gets to doing these kinds of projects, it's very informative.

[astrnmrtom]

Nice job!

Part of the attraction of installing solar was the fun of designing and installing the system myself. I really enjoyed the project. On the practical side, it's nice having the system just work silently without any input from me. I have both an onboard generator and a small portable as a back-up but it's nice to have the sun do all the work silently most of the time.

The initial driver for me was the need to run off batteries only once a year in a place where generators weren't allowed. I didn't have enough wattage to keep the batteries fully charged, but it did extend the discharge time long enough to get me through the four days of boondocking. Eventually, I rebuilt the system to handle boondocking with a residential refrigerator and it's worked great so far. As long as the sun is shining, the limit on how long we can boondock is our holding tanks. With 600 watts we do have to do some power management, but I can't say we feel we have to give up any comforts to boondock.

I occasionally think I'd like to add some portable panels for additional flexibility, but storage is an issue right now - I just have too many other toys taking up space.

[AlanTerry]

SJ-Chris tank you for posting your installation.

[Old Scout]

Nice job at a good price....you certainly made sure your panels are fastened to the roof. Where do you get your Dacor?
PS --suspect your next upgrade will be batteries--with so many choices these days, you will never be satisfied with just three 12v L/As--smile....

[paul65k]

Originally Posted by astrocamper

I have been using solar since 2009. The first 8 years I had 240 watts of solar, 1000 watt inverter and a pair of Trojan T105 batteries. The system worked great and I just had to add water every few months. Batteries were in great shape when I sold the 5x8 cargo trailer.

My larger Artic Fox 22G has 1440 watts of solar and a VE Multiplus 3000VA inverter charger and a larger LiFePO4 battery bank. I love the quiet of solar and the ability to not have to worry about running down my batteries. I have power when I need it.

I am sure you will enjoy the solar on your trailer. Since you installed it yourself you can appreciate how much you saved verse contracting it out. Hope you get a lot of years out of it.

Same here Jeff....first system was a 2008 install from AM solar. A whopping 400W of panels, 30A MPPT controller, Magnum MS2812 inverter/charger and 6 Lifeline AGM batteries, all for only $8,000.....thank goodness it was already installed on an Alpenlite 5th wheel I purchased. I learned a lot on that one, replaced a failed Inverter, replaced the 4 100W panels with 3-200W panels and realized when we got our next rig I'd build the system to the max.

Today I have a pretty complete system with dual inverter/chargers, 1600W of solar and a complete re-wire to run everything in the coach with 840Ah of LiFePO4 batteries. It was expensive but I did it all myself and the system does everything I want and I can monitor it from anywhere, but................. If I were to do another one it would be just as capable at about 1/3 the cost with what I know now about using residential panels and DIY Batteries......it's amazing how far we've come with solar in RVs in just a little over a decade

[SJ-Chris]

Originally Posted by AlanTerry

SJ-Chris tank you for posting your installation.

Glad you and others have found it useful! I've learned so much from these forums, so I want to do my best to help others likewise.


Happy Camping!
Chris

[SJ-Chris]

Originally Posted by Old Scout

Nice job at a good price....you certainly made sure your panels are fastened to the roof. Where do you get your Dacor?
PS --suspect your next upgrade will be batteries--with so many choices these days, you will never be satisfied with just three 12v L/As--smile....

Out of convenience, I got my Dicor at a local Camping World. Not sure if it was the best price, but I was fine with it.


Regarding batteries...I'll get the 3rd lead acid battery installed and have 300AH with 500w of solar. My fridge runs on propane when not plugged in. I've boondocked in 40 degree weather and in the morning (after a couple hours of TV at night, and charging phones, and the furnace, etc) I think I was only down ~60AH.


For me, for the foreseeable future 200-300AH of cheap lead acid will be plenty. I do not believe in the "Don't let your LA batteries go below 50% capacity" mantra. I think it is perfectly fine if once in a while they drop down to 25-30% charged (discharged 70-75%) as long as they get charged back up as soon as possible. I don't boondock very seriously, and I also have an onboard generator if needed. But it sure is nice not having to worry about battery power (so far)! So far after about 10 days of boondocking over 3 different outings, I think the most discharge I've seen is about 30% (in the early am as the sun is coming up). Then the solar kicks in and it quickly gets me back up to 90-95% in just a few hours.



-Chris