My Solar Panel Installation

[Airmon]

Part 1 - Planning

Last year, after some thought and planning of future trips in our RV, we decided to install solar power on our 29’ Holiday Rambler Traveler class A RV. This document is going to cover my experience with my DIY installation and the decisions I made in the process.

About me: I have no professional training, but I have been messing about with electrical stuff most of my life. Mostly this seems to have amounted to fixing some hooptie vehicle I own, but it’s been its own reward. I also have a little experience with solar power. For a few years in the 90’s, when I lived in Key West, I owned an electric car that had 240W of panels on a tilting mount on the roof that could slowly charge the car. I also installed a 60W panel and a 7A charge controller in our first camper.

Still, I did a lot of reading, mostly of sources on the Internet. Here are some of the informational resources I used:

http://jackdanmayer.com/rv_electrical_and_solar.htm - Lots of good info.

http://where-rv-now.com/Notes/Solar/ - My brother’s site. Handy solar calculator there, too.

http://h andybobsolar.wordpress.com/2011/01/19/welcome-to-handybob-solar/ - Bob’s kind of a curmudgeon, but a knowledgeable one.

http://roadslesstraveled.us/solar-power-rv-boat-installation/ - Includes tutorials.

http://www.amsolar.com/home/amr/cpage_9/rv_solar_education.html - I bought a lot of my solar components from these guys, but they have some good information, too.

Additionally, almost every manufacturer has a website with technical documents that will be invaluable in planning your installation and in operating it afterwards.

About the RV: Our 2003 29’ Holiday Rambler Traveler came from the factory pretty well equipped for power independence, with a fairly large battery bank of four 6V batteries, a 5.5kW generator and a Xantrex 1500W modified sine wave inverter/charger. The Xantrex works well as a charger, putting out a maximum of 75A back into the batteries, so just a couple of hours of generator operation will bring us back close to full. Our house battery system charges fast from the chassis alternator as well, so if we have a driving day moving from one site to another, it will mean that we’ll arrive with full batteries. We’ve got a lot of roof space, so large panels are fairly easy to place. Finally, it’s got a fair amount of basement storage, so finding a spot for a controller isn’t a big deal.

Inside the RV, I’ve changed over to LED’s in many of the spots where we had incandescent light bulbs that saw frequent use. I’ve also removed the old 24” tube TV and replaced it with a low power consumption 26” LED 12V TV. All of our device charging needs are met with 12V chargers, so we don’t need to turn on the inverter to charge a phone or a laptop.

I started by looking over our energy consumption, watching my 12v battery monitor on several trips. In my opinion, the first thing anyone who’s boondocking or concerned about understanding their 12V power situation should do is install some sort of power monitoring system. This will tell you how many Ah you’ve pulled from your battery system. Simple voltage monitoring is not the same. Do this BEFORE you buy anything else.

I’d suggest either:
LinkPRO or LinkLite from Xantrex ( I have the linkPRO and like it a lot )

Trimetric from Bogart Engineering ( I’ve used it and thought it was pretty good )

Clipper BM-1 from NASA Marine ( limited to 100 Amps, but they make it in a small surface mount version )

All of these will work like a gas gauge for your battery bank, telling you how much power remains in the batteries. They do this by measuring all the current going into and out of your battery pack and comparing it to the known capacity that you program into the unit.

After a few trips doing some dry camping, I’ve come to the conclusion that we can manage pretty happily on about 80Ah per day, as long as cold weather doesn’t force us to run the furnace a lot.

Our battery bank is four 6V batteries, each rated for 235 Ah, wired in series for 12V, with the two 12 sets in parallel for a total of 470Ah @ 12V. If we discharge our batteries to 50% discharged, we have 235Ah of usable capacity.

235Ah ( usable capacity ) divided by 80Ah ( daily usage ) is 2.94 days of power out of the batteries before we’re at 50% discharged. Colder ( requiring the furnace ) or hotter ( requiring the fan-tastic vent fans ) days will require more power and we will get less time out of our batteries.

I expect that as we learn more about our usage patterns we’ll get better at conservation, but we’ll probably be using our computers more and that’ll increase the need for power. I’m hoping it’ll balance out somewhat.

In the end, I settled for a goal of being able to put back 100Ah per day or better. If it doesn’t meet its goal every day, that’s OK. More power daily would be better, of course. I figured that a 500 Watts solar installation would work for me.

My most challenging issue was how to get the power from the roof to the controller without a long wire run that wastes power, or where I’d go through the interior of the coach. My refrigerator vent is on the side of the coach, so that wasn’t an option, and everywhere else that had a space I could drill through the roof and run the cable didn’t have a good path to the basement compartments. In the end, I decided to run it down alongside the tank vent and use heavy 4 gauge wire to limit voltage drop as much as I could, despite the long cable run.

I found a good deal on a MPPT controller from a company in Canada, so I ordered a Blue Sky Energy Solar Boost 3024iL and the battery temperature sensor so the controller could temperature compensate the charge voltage to the batteries. I chose this controller for several reasons.

It was in the wattage range I needed, though buying bigger always gives you the option to add more panels, a bigger MPPT seemed to be a jump of about $300.
It would fit well in the compartment I planned for it.
It had an additional 2A charge port for the chassis battery on the RV, assuring that it would always remain charged when the RV was parked, without any additional circuitry.
Good quality and track record, from what I could find on the Internet.

I liked the idea of being able to tilt my panels and liked the quality of the stainless steel panel mounts from AMSolar, so I ordered three of their 160 watt panel kits with mounts and 10/2 ( 10 gauge, two conductors ) wire. I also ordered a combiner box for the roof, and some 4 gauge wire to go from the combiner to the controller and then on to the battery bank from AMSolar as well.

The folks at AMSolar were very helpful before my purchase, answering questions and helping me understand exactly what I needed for my installation. One of the panels was damaged in shipping ( it looks like UPS punched a bolt-sized hole in it ) and AMSolar was quick to replace it. Also, while I bought three panels, each with 15’ of 10/2 wire, three 15’ segments would have been inconvenient, being too short where I planned to put one panel, and too long for another location. So they let me buy another 10’ of 10/2 cable and sent me a single uncut 55’ length, which I could cut to length as I needed. Very nice.

To max out the capacity of my controller, I decided to add one more panel, so I got a 60 Watt panel from Amazon and some inexpensive aluminum mounts. I knew that I couldn’t tilt it like the other ones, but I couldn’t find a 60W panel that would fit the other mounts. I also ordered some of the other assorted items I would need from Amazon as well, like the panel disconnect switch and the circuit breaker/battery disconnect. I also got cable ends, Dicor roof sealant and 3M VHB ( Very High Bond ) double sided tape for attaching the 60W panel and the junction box to the roof.

This would bring the panel wattage up to 540 watts, the maximum the controller would allow at 12V. Actual wattage will be lower in normal conditions, but I figured this would get me to my 100Ah/day goal.

Using my brother’s solar calculator, I should be able to get 100Ah or more per day ( in sunny conditions ) in any part of the US I’m likely to go in my RV, in any of the seasons that I’m likely to go there. So, while I can’t get 100Ah in Wisconsin in December, I’m unlikely to visit then. In the south, in the summer, I could get as much as 250 Ah per day. That’ll do.

The calculations don’t take into account the possibility of tilting my panels, so if I’m somewhere for a while during marginal sunlight times, I may be able to adjust my panels to get additional power.

Next: Assembling all the bits and installing the wiring under the RV.

Photos here - https://plus.google.com/photos/101533552838802518081/albums/6002206624346422593?authkey=CNKhpNigsd_D...

[Airmon]

pianotuna wrote:

Since you used nominally 12 volt panels MPPT technology was not needed.

A 30 amp controller can not accommodate all the output at solar noon from 540 watts of panels.

The input side of my controller is limited to 30A. The output side of my controller is limited to 40A if 12V in and 12V out ( nominal voltage ) like I am.

At maximum power point, my 160W panels are rated for 8.65A ( x3 for 25.95A ) and my 60W panel is rated for 3.3A, for a total of 29.25A.

It's possible that the MPPT feature might mean that marginally less than 30A into the controller could result in just over 30A out, but that's not really the reason for MPPT for me.

If it never gets over 30A, that's fine. If I close to that output, I'm getting enough power ( 200+ Ah/day ) to live my chosen RV lifestyle. It's the cold, off-angle days I'm hoping the MPPT pays for itself, eking out every last bit of power out of the cells.

YMMV.

I'll see, I guess.

Thanks for the reply!

[Airmon]

Part 3 - Results, lessons learned and component list with pricing

I had to work the next day, but when I tested the system the following weekend, I saw a max of 26.2A going into batteries that were just 3% drained by heating a cup of water in the microwave for a few minutes.

Interestingly, this current is a little under what my brother’s solar calculator ( http://where-rv-now.com/Notes/Solar/#Calculator ) comes up with as the theoretical maximum for my panels on the date they were measured. I think that means the system is working pretty well.

If we assume that the calculator is accurate ( now that we have a number that seems to match ) this means that my panels will, on an appropriately sunny day, put out my goal of 100Ah or better until mid November in any latitude I’m likely to visit at that time. Actually, if I’m that far North at that point in the year, I’ll be looking for shore power for a heater.

Mission Accomplished.

As for the lessons learned, well, I didn’t cover this much in the planning post, but I had originally seen the 3024iL listed as a 40A controller, which it kind of is under certain conditions. So, I had originally planned on purchasing four 160 Watt panels ( rated at 9.6A Short Circuit each ) for 640 watts, rather than the 540 I ended up with.

However, once I got the controller in hand and read the manual, I discovered that the 40A rating is only the OUTPUT side of the MPPT controller, and only when the input side is using 12V panels going to a 12V system. Under all circumstances, the input side is limited to 30A.

The controller can take 24V input, but then maximum power is limited to 400W.

This meant that I couldn’t use the four 160’s I had originally planned, either in series or in parallel. So I cut back to three 160W panels and added a 60 Watt to round my output to the controller maximum wattage at 12V of 540W.

The lesson: If you’re doing the planning and install yourself and you don’t have extensive experience with this stuff, you need to hit the internet, download the MANUAL ( not just the spec sheet ) and READ IT. Particularly if you’re operating anywhere near the limits of the equipment.

The good news is that I did eventually read it before I ordered my panels and so the results I got are still within my original goals, even if they’re 100W down on my first plan.

Issue 2: The installation required something like a dozen trips to the hardware store for little fiddly bits that I didn’t realize I needed until I actually tried to assemble the whole deal. 2 tubes more sealant than I had figured, stainless hardware, butt connectors, more cable lugs after I crimped two of them poorly, that sort of thing.

The lesson: unless you live RIGHT NEXT TO hardware store and an auto parts store ( a good place for high power battery connectors and stuff ) get extras of almost anything that you need multiples of, can be thought of as “supplies” and isn’t very expensive. $30 worth of that kind of stuff before I started would have saved me a weekend of putting the installation off because I didn’t have everything and $20 in gas running to the hardware store in the middle of the job.

Issue 3: The job took way longer than it sounds like in my description. Just running the wiring around on the underside of the RV took most of a week of after work labor crawling around by myself under the RV. After that it was most of two days assembling the panels and getting everything installed on the roof, since there were complications with the roof vent installation that I didn’t cover here.

The Lesson: Guess how long it’ll take and double it.

The complete parts list and costs:
Three 160W panel kits $1080.00 AM Solar
Roof Combiner box $72.00 AM Solar
35' 4/2 cable $175.00 AM Solar
10' 10/2 cable $25.00 AM Solar
3 cable seal $9.00 AM Solar
4 4AWG lugs $4.00 AM Solar
Shipping $58.00 AM Solar
Four tubes sealant $30.00 Amazon
10 tinned copper lugs $10.00 Amazon
3M VHB tape 3/4" $20.00 Amazon
Renogy Z brackets $13.00 Amazon
50A circuit breaker $29.00 Amazon
High current switch $24.00 Amazon
Plumbing vent kit $6.00 Amazon
60W solar panel $105.00 Amazon
3024iL and temp sensor $275.00 WeGo Solar
Cable ties $6.00 Home Depot
Nylon cable holder $2.00 Home Depot
Stainless bolts $6.00 Home Depot
Silicon sealant $4.00 Home Depot
Expanding foam $6.00 Home Depot
5A fuse holder $2.00 NAPA auto
15' 16/2 wire $10.00 NAPA auto
Crimp connectors $4.00 NAPA auto
Self Tapping Screws $2.00 Home Depot

Total $1,977.00



Note: The Solar Panel kit from AM solar included the panel, mounts, 15’ of 10/2 wire, cable ties and cable tie mounts, VHB tape.

AMSolar was very helpful, answering a bunch of questions or confirming the decisions I had made. They also helped to make sure I got all of the specialty pieces I would need in one order. I would definitely order from them again.

Amazon is tough to beat for cheap prices and fast, cheap shipping, but you get almost zero support, so it can be tough to put together a package without any missing bits. Still, if you had the right installation, you could put together a 400W MPPT system from Amazon for about half what I paid for my 540W one, though you’d have to make some compromises.

In Conclusion: Over the course of a few months of planning and ordering, followed by a couple weekends of messing about on and under the RV, I successfully installed a high quality 540 MPPT solar system on my RV for just under $2000. I’m pretty happy with that.

Thanks for reading. Feel free to email with questions: airmon at gmail dot com.

Note - Pictures of many of the components and the installation are at https://plus.google.com/photos/101533552838802518081/albums/6002206624346422593?authkey=CNKhpNigsd_D...

[MrWizard]

pianotuna wrote:
Hi,

Since you used nominally 12 volt panels MPPT technology was not needed.

A 30 amp controller can not accommodate all the output at solar noon from 540 watts of panels.

Enjoy the system.

All if means is at solar noon, if the batteries need it they will get 30 amps instead of 39 amps

But what it really means, is that he will get close to 30 amps long before Solar noon, and by SN, his batteries will have received enough charge, they will no longer be absorbing that much and would not accept 39 anyway

I have 505w of panels and a 25 amp blue sky controller, and very seldom see 25 amp battery charge

The rare occasions are when the cloud cover/overcast breaks up late in the day and I get full solar output with batteries at low soc

His controller will limit to 30a, there will be no damage or problems

[RoyB]

I'm looking for PART 3 as well. I would think about using the generator maybe for an hour or so to get the initial HIGH CHARGE AMPS demand from the 50% SOC batteries down to around 15 AMPS before shutting off the generator and letting the panels take over. I think this is going to be the trick that will save my day with my planned 360WATT solar panel setup. My battery initial demand when I hit them with 14.4VDC smart mode charge is around 52AMPS DC current from my on-board 60AMP smart mode Controller and this will drop down after an hour or so of charge. Then I can use my solar panels to finish the 90% charge without the generator before the high sun goes away... I am only going to expect around 18AMPS of usable DC current being produced from my three 120WATT Solar panels during high sun.

Being OLD SCHOOL I will not start my nightly run off the batteries unless they are at the 90% SOC state and when the batteries hit their approximately 50% SOC I will shut down operations until I re-charge.. Being planned out this should occur at 8AM the next morning when I can run my generator.

Roy Ken

[westend]

Waiting on part three, of course....:B

BTW, really well written project compilation, I've got it bookmarked.

[pianotuna]

Hi,

Since you used nominally 12 volt panels MPPT technology was not needed.

A 30 amp controller can not accommodate all the output at solar noon from 540 watts of panels.

Enjoy the system.

[Golden_HVAC]

500 watts should keep it well charged.

Many think that a single 60 watt panel will do, however the RV will consume more power in one day than my 120 watt panel can put back in a normal day. The CO detector, propane leak detector and refrigerator will all combine to use about 35 amp hours per day.

Good think I have a pair of 120 watt panels and a 75W panel. I have a 50 amp controller, and have space to improve the system when needed.

Fred.

[Airmon]

Part 2 - Installation

As mentioned earlier, UPS damaged one of the panels, so there was a delay while AMSolar shipped another one.

In the meantime, I laid out all of the other components on a table like a big schematic and walked through all of the steps I had ahead of me and checked to see if I thought I had all of the parts I’d need. Of course, there were the inevitable couple of trips to the hardware store, but after going over it a couple of times I was pretty sure I had all the specialized components I’d need. This also gave me a chance to prep some items, like the wire seals and holes that needed to be installed in the combiner box, or the cable clamps in the knockouts on the controller.

When my replacement panel arrived, I was ready to start.

I began by mounting the controller in a compartment close to the batteries and pulling a pair of 4 gauge wires from there to the battery box. I mounted the 50A marine circuit breaker in the battery compartment inline with the positive. I went ahead and connected it to the batteries, but I left the breaker open so the rest of the cable was disconnected. I also ran the temperature sensor into the battery box and the chassis charge wire to the chassis battery disconnect switch in one of the front compartments, connecting to the battery side of the switch with a 5A fuse.

All of these connections, with the exception of the controller ( which had large screw terminals for bare wire ) required crimped on lug ends of one size or another.

Note - If you’re going to do this yourself, most of what you need are normal hand tools, but if you’re going to be working with wire heavier than 10 gauge, I suggest getting a good pair of cable cutters ( http://www.amazon.com/Greenlee-727-Cable-Cutter-9-1/dp/B001RSMPWU/ref=pd_cp_hi_3 ) and crimpers ( http://www.amazon.com/Klein-J1005-Journeyman-Crimping-Cutting/dp/B000936OTY/ref=sr_1_17 ) .

From the controller compartment, I had to run more 4 gauge cable up to the roof where the panels and the combiner box would be. I chose to run it up along side my black/grey vent pipe at the rear of the RV. This made for a rather long wire run, which is why I chose to use 4 gauge wire for this. If you have a refrigerator vent, I suggest using this route to get the power down from the roof.

I tied the wire along the back frame of the basement storage, going over the suspension on the chassis framem taking care to keep the wire secured with wire ties and up out of any of the points where the suspension would move.

On my RV, there’s a panel on the passenger side of the tank compartment that removes with about a dozen screws, exposing the ends of the tanks and the bottom of the vent pipe that goes up through the roof. With the tank ends exposed, I could see an open spot in the bottom of the compartment to drill a hole to pull the wire up. There was extra space around the floor where the vent went through, so I pulled the wire up through there. I then sealed the floor space around the cable with expanding foam and the bottom of the compartment with silicon sealant and put the cover panel back on.

I tied the wire to the vent pipe with plastic wire ties and ran it up to the ceiling of the RV. On the roof of the RV I removed the vent and cut a large enough hole in the side of the vent for the wire to exit. We replaced the vent ( now with the wire running through the side ) and covered the base and the wire exit liberally with sealant.

With the wire runs done, we took the cardboard that protected the panels during shipping and put them up on the roof to use as templates to figure out where we were going to lay the panels on the roof, as well as how much 10 gauge 2 conductor wire we would need to go from the panels to the combiner box.

With the panel locations penciled on the roof and the wire runs planned, we got back down and prepared the panels. First, we cut the individual runs to length and marked each panel with tape and a sharpie so the right panel ( with the right length of wire ) went into the right position. Then we crimped the wires from the panels to the cable runs and put heat shrink tubing over that to protect them. Finally, we attached the mounts with the included bolts and taped cardboard over the panels so they would not be putting out power while we connected them.

My RV has an aluminum roof, so AMSolar had suggested that the 3M VHB double sided sticky tape was sufficient to hold them in place on the roof without any additional screws and thus additional roof penetration leak points that come with them.

We carefully handed the prepared panels up to the roof and set them in their positions, laying the cables back to the combiner box, with a foot or two to spare. Where the cables ran alongside one another we tied them together with plastic cable ties ties ( use the black ties for UV resistance ) and stuck it to the roof with a cable tie mount. When we were sure we were happy with the position of the panels and the wiring ( make sure to leave enough extra wire to tilt your panels if you have tilting mounts!), we cleaned the roof well with rubbing alcohol and stuck down the mounts.

Next, we used VHB tape to stick the combiner box to the roof. We then ran each wire into the combiner box, cut it to length, stripped the ends and fastened them to the busbars inside the box. We did the same with the 4 gauge wire going down to the controller through the RV and put the cover on the box.

Then we went back and sealed around all the panel mounts, cable mounts and the combiner box. You want to totally cover the VHB tape to keep sun and rain off of it, to prevent degradation to the adhesive.

We removed the cardboard from the panels and we were done! Unfortunately, it was dark out by this time, so we didn’t have any idea if it worked.

Details on how it came out, what I think I learned from this, and a mostly full component list with pricing in part 3.

Note - Pictures of many of the components and the installation are at https://plus.google.com/photos/101533552838802518081/albums/6002206624346422593?authkey=CNKhpNigsd_D...