Although I have written elsewhere in this blog regarding different aspects of our interest in solar for our motorhome, it occurs to me that I should dedicate a specific section to our solar project as means of documenting the design, purchases and installation. So, hear goes.
Our motor home is a 32 foot Bounder. It came with a single 12 volt “start” battery, and two 6 volt golf cart “storage” batteries wired to produce 12 volts. Most of our RV travels have included staying in private campgrounds with full hook-ups. We did very little boondocking. But when we did, I will always remember being shocked at how fast the storage batteries were depleted. A couple days in the bush, and we were through. Compounding our problem, was the fact that our generator never would run for long no matter what adjustments we made or how much money we threw at it. It wasn’t a difficult decision for us to consider solar as a supplemental source of power generation. Our challenge is to have a battery bank with more storage capacity than what we have been used to and to have a means of charging the batteries without use of alternator or generator.
After a fair amount of research, we asked ourselves what is it that we wanted to achieve with solar power. We know that the energy produced by 400-600 watts of panels will not run EVERYTHING. But we also know what we have at present, and that it was not going to be sufficient for what we have in mind when we go on the road full-time. The factory battery set-up with on board convertor/charger always worked fine as long as we stayed in full-hook-up RV Parks and campgrounds because, since you are always plugged in to shore power, you always have batteries topped off. But our plans in the near future will include less RV Parks, and more boondocking.
As mentioned, our Onan genset that came with the Bounder has never run very long or at all. It’s virtually new because of its lack of running. And, of course this was made worse because it wasn’t run enough. Kind of a vicious circle. So we have decided that the Onan will be removed and the space will be converted to a vented battery bay, at least initially containing four (4) 6-volt golf cart deep cycle batteries delivering an “advertised” 440-460ah at the 20 hour rate.
Our intent is to use a generator minimally. But as a means of back-up power we have purchased a 3500 watt portable “RV” generator. It will store in a separate compartment from the battery bay.
Another thing borne out of our research, that did not take long for us to act on, was to include a battery monitor in our plans. It’s amazing to think that during all our “RV” years, we never had a in-house battery monitor that could graphically display useful information regarding our batteries 24/7. Ultimately, we went with this one, a Bogart TriMetric TM-2030…
9/28/14 Update: We took pains to educate ourselves as to which way to go when it came to selecting panels. We considered Monocrystalline vs. “Poly”, wattage, voltage & amps, and physical dimensions, among other things. We also considered cost per watt, quality of construction and company and product reputation.
In the end, we went with a company called Renogy. Based out of Baton Rouge, LA., they have warehouses in other locations, including in Chino, California near where we are located. The company offers some pretty good bundled deals on EBay, which we took advantage of. From the time we placed the order on EBay, we received the panels within 48 hours. And shipping was free, which is saying a lot because the two packages had a combined weight of 88 pounds. Ultimately, physical dimensions played a critical role in our decision. Renogy offers a panel dimension of 47″ x 21″. This is ideal for working around roof A/C units, of which we have two.
Our plan is to start with four Monocrystalline 100 watt panels, anticipating expansion to six panels. So, 400 watts to start, and 600 watts ultimately. One of the first things I did was to create a layout of the roof of the motorhome showing all roof obstructions and the panels. We tried to draw everything to scale.
Last week, we received the panels. After unpacking, we tested the VOC and ISC using a multimeter, and found them to be as advertised. Voltage was 22 volts, with amperage well above 5 maps.
Because we intend to have the option of tilting the panels, I looked online at different designs that were being used. I was attracted to one particular design that seemed simple but sturdy, using readily available aluminum angles and straight pieces. Unfortunately, these brackets were on EBay for $100+ per bracket. That would be totally outside our budget. Because I have the tools and fabrication expertise, there is usually no way I will pay for something I can build myself. So, this past weekend, I began the process of building the brackets, the materials for which all came from Lowe’s.
This type of work includes working with pieces of angled aluminum. Lots of cutting and drilling. Pretty basic, but satisfying as pieces are replicated for each of four panels. And, of course there is assembly of the first bracket as a test of how well things are going. In the end, I was pretty satisfied with the progress made.
10/1/14 Update: I have continued to work on the tilt brackets, making a fair amount of progress in the last few days time permitting. One of the things I had to deal with is the fact that our Bounder has a rubber roof with a plywood core underlayment. My readings have revealed that typical sealing caulks may not be suitable for rubber roofs. Consequently, I ordered what I hope is the correct product for the job. It’s a “Advanced RV EPDM” product for rubber roofs. My intended use is for water proofing the threads of screws and sealing of screw heads in conjunction with my tilt brackets. I received the product today. We’ll see how it goes. And if I need more, at least I know where to get it.
Also in my research, I kept coming across suggestions that I will probably need a combiner box on the roof of the motorhome. As a reminder, our system will start off using 4 100 watt panels, eventually expanding to 6 100 watt panels. Each of these panels are pre-wired with MC-4 connectors. And because there are a varied selection of UV resistant MC-4 branch connectors, extensions, etc. available to complete the on-roof wiring, I was confused as to the need for a “combiner” box. So I called Renogy, my panel supplier. I spoke with one of their tech reps about combiner boxes and he indicated that they really only use them in “kilowatt” systems, not for a few panels on the roof of an RV. He mentioned that MC-4 connectors were all that should be needed running to the charge controller. So, that’s my plan. I’ll do some more research and inquiries, but unless there’s some reason I’m unaware of for having a combiner, I will not use one.
10/2/14 Update: Today is charge controller delivery day according to the tracking email I received. Using some of the proceeds in our PayPal account as a result of sales of items on EBay, we decided to go with the Morningstar TS-60 MPPT charge controller. Depending on who you talk to or read from on the internet, Morningstar products are among the best. And this particular unit gets great reviews and is plenty enough for what we have in mind, now and in the future.
10/07/14 Update: We are very close to lifting the panels and integrated tilt brackets up onto the roof of the motorhome. Constructing the brackets has not been difficult, but is tedious. Lots of hand cutting and drilling, as well as filing and sanding pieces to shape. Here are some photos…
This is a stock section of angle aluminum, drilled with a sufficient number of holes to provide infinite “tilt”, depending on angle of the sun during peak charging hours. Each section of angle aluminum was rounded to keep me from injuring myself.
The strut bars are 1/8″ thick by 1″ wide. Each bar was cut to length to allow for an angle of 45 degrees when fastened to the outermost holes of the brackets. Different angles can be accommodated using the same bars. Time will tell whether these particular bars will be stout enough. If not, they can be replaced with thicker stock. They seem pretty solid when “bench” tested. We’ll see.
This photo shows a completed bracket. As mentioned, there are no shortage of adjusting holes, most of which may not be needed. But who knows. The brackets incorporate nylon spacer washers and are designed to collapse and be self-contained when flat on the roof. An added benefit of the angled aluminum is that the panels will have plenty of clearance for air to pass underneath, aiding in cooling when the panels are not tilted.
Here is what the nearly completed panels look like when tilted by their new brackets. So, what’s next you might ask? Well, once we purchase a few more fasteners that we ran out of, we will be ready to hoist the panels onto the roof of the motorhome, and after final positioning, we will begin screwing them in place and then sealing the screws and screw holes.
10/13/14 Update: This past weekend, after having placed the panels on the roof earlier in the week, we fastened the panels WITH tilt brackets to the roof. The roof thickness seems to be about 1 1/2 ” hollow-core plywood below the rubber. I chose to screw the brackets to the roof using 1″ screws. This meant that the screws are only penetrating and being held by the thickness of whatever plywood thickness is represented by the outer sheath. Each bracket includes at least 10 screws over a 24″ span. Except for some shims that I will need to place at the end of certain of the brackets, the screws seem to be doing the job. Time will tell . I will be posting photos shortly.
12/04/14 Update: Wow! It’s been awhile since I last updated this page. A lot has happened since back in October. First of all, I need to correct my assumption about our particular roof. I had indicated in the update above that the “hollow-core” was made of plywood. It seems that it is actually a hollow-core of either plastic or fiberglass. This is below the rubber roof. As a consequence, my screws were NOT holding as well as I originally thought. Before drilling WAY too many holes in the roof, I decided I needed a better solution. This is what I came up with…
These are hollow wall anchors, the type you would use in your home for hanging things when a screw might not work. After some experimentation, I decided on a size that had a very short neck just below the lip that you see in the photo. After even more experimentation, I decided to use four (4) anchors with EACH bracket, four brackets per panel…so 16 anchors per panel. I can confidently tell you that this set-up works. This is a very strong solution. And yes, I know, I drilled into the roof which is verboten. My rationale is that I only went thru the outer portion of the hollow-core AND I used EPDM sealing caulk (for rubbber roofs) sufficiently to insure there will be NO water seeping in. There was another benefit to going with this solution. Originally, I had planned that the lower “angle” of each tilt bracket would be screwed directly to the roof, lots of screws. But beyond the screws, this proved problematic due to the curvature of the roof, and my Bounder’s roof curvature might be more than other rigs. So, what I ended up with is a MUCH BETTER solution. This is what the panels look like mounted and caulked and tilted…
So once the panel mounting was essentially complete, it was time to decide how I intended to run the cables from the panels to the battery bay which will be in the compartment that formerly housed the Onan Genset which was removed and replaced by a portable that stores elsewhere. The compartment for the batteries is located on the driver side behind and below the driver. The original plan was to use some of these to connect the panels together in parallel…
Panels generally come with 12 gauge wires. Although I had intended to run 10 gauge extension cables to these branch connectors, I also became educated that 4 awg welding cable was probably the best way to go from the roof down to the charge controller so as to minimize voltage drop. This made me start thinking about a combiner box on the roof so as, among other things, I would have a transition junction from 10 gauge cable to 4 gauge. After more research, I started piecing together the components of a combiner box. I knew I wanted each panel to essentially plug into the box, and I knew I wanted each panel to have its own circuit breaker. I also needed some form of junction block to funnel 4 positive and four negative cables down to two 4 gauge cables (+ and -) that would exit the box and be routed to the battery bay.This is what I assembled. Right or wrong it is my own design…
The box came from Home Depot. The brand is Cantex and the size is 8″x8″x6″ deep. The DIN rail was found on ebay cheap. I cut what I needed from the two 8″ pieces I bought. The four circuit breakers are 15A MidNite Solar products purchased on eBay. The junction blocks are used for car audio applications 4 into 1. The fittings on the side are water tight fittings from Home Depot. The MC4 connectors and wiring were cut from extension cables. Time will tell whether this is a good setup. I believe it will be but I’m a solar newbie.
Two 25 ft 4 gauge welding cables, one for positive and one for negative. The beauty of using welding cable is that they are extremely flexible. Much more so than typical electrical wire. This is due to the outer “shin” which is almost like neoprene rubber but much more durable. The reason I only needed 25 ft pieces is because of my decision to run these cables from the combiner box to be mounted directly behind the front roof AC, straight over to the roof edge and directly down to the battery bay on the OUTSIDE of the motorhome. I know this may sound weird but it has benefits, not the least of which is MINIMAL voltage drop. The cables will run thru 1/2″ PVC irrigation tubing mounted to the exterior of the Bounder. It has been painted to match the Bounder. Although I may eventually fabricate a thin aluminum cover for the PVC, here is a photo of what it looks like so far, which also shows the proximity to the vented battery bay…
12/29/14 Update: Yikes! It’s almost the end of 2014, and my solar project is not finished. I must admit that this project has taken longer than I originally anticipated. Mostly, because I’m learning as I’m going. And also because I really want to do a good job and, as I get to certain points along the way, it occurs to me that some small part or whatever might make for a cleaner install. Generally, this has meant running to Lowes or Home Depot. But more often than not, it entails ordering something on eBay or Amazon. When this happens, it takes a certain number of days to get the item and, so, the process slows down. Such is the case at the moment. I’m waiting on parts.
So, where am I? What follows is a review and status as of today Monday, December 29th.
-The four 100 watt solar panels are installed, complete with tilt brackets. Everything is caulked and sealed.
-A homemade combiner box, complete with circuit breakers, is finished and installed on the roof directly behind the forward air conditioner ( see photo above).
-4 gauge positive (+) and negative (-) welding cable has been installed from the combiner box to the edge of the roof and down thru 1/2″ PVC tubing attached to the side of the motorhome running directly to the solar equipment compartment and battery bay.
-The solar equipment compartment includes the installed, and partially wired Tristar MPPT 60 charge controller, as well as the installed and partially wired Baby Box with circuit breakers. The two 60 amp breakers additionally act as disconnects between panels and controller and between battteries and controller.
-Four new Interstate GC2 6v golf cart batteries have been purchased, installed and wired. They have been wired in series-parallel to produce 12 volts and 440ah.
While waiting for the latest small parts relating to wiring, I am working on a lid to be utilized in the battery bay to essentially seal off the top of the batteries. The bottom of the battery bay is open-air by intent for ventilation. Additionally, the battery bay door is partially screened for cross-ventilation (see photo above).
Coming attractions include extending and re-routing of necessary existing wiring from the front of the coach to the battery bay and otherwise completing the wiring relating specifically to the solar install.
01/21/15 Update: I was beginning wonder if I would ever say this, but our solar project is done. Well, at least to the point of an operating system. There are still some wiring issues NOT related to the solar system, due to the fact that the battery bank is now on the side of the Bounder, as opposed to its original location up front. And there is still some minor construction of a battery bank lid, so as to make the battery bank more of a separate compartment from the solar charge controller and related circuit breakers, etc. Here is a photo of the solar and battery bay.
At present, I am getting familiar with the solar charge controller. And, at least for now, these storage batteries are not connected to the coach. Consequently, there are no loads being applied to the batteries as yet…but soon. As a reminder, I’m using 4 100 watt panels wired for 12 volts. The four 6 volt GC2 Golf Cart batteries are wired in series and then parallel, producing 440ah. Although there is a possibility that we will need to add more panels (we have room), at least for now, we’ll see how the system works for us.
3/15/15 Update: It’s amazing how time flies since my last update. Even though I have made progress with little things relating to the overall electrical system, I have not posted in nearly two months regarding our Solar Project. Nevertheless, today is very timely since yesterday was our first real test of the system’s charging abilities.
It should be pointed out that throughout this entire project, I have learned SO much. And I’m still learning. As a case in point, once I had everything hooked up and “working”, I was having trouble understanding the digital data I was getting from the charge controller. Among other things, it seemed like I was not producing much in the way of amps.
After some online research and feedback from those more knowledgable with solar and batteries, I came to realize that not much happens when the batteries are fully charged, which was the case with the house batteries. As a reminder for reference, these are four (4) NEW GC2 Costco (Interstate) 6v Golf Cart batteries. They are wired in series (2 and 2) and the the two pair are wire parallel. The result is 12 volts and 440ah produced by the 4 batteries.
So, realizing that the batteries needed to have some level of discharge before conducting a test, I spent three days discharging the batteries. But first, let me tell you that during the last week, time permitting, I installed my TriMetric 2030-RV monitor. This allowed me to “monitor” real-time battery voltage, amps, watts and battery “percent full”, among other things. This is a great battery monitor that allows you to get real familiar with all your various appliances, and the amount of amps they draw when turned on.
TEST #1: As I mentioned, I spent three days leaving lights on for far more hours than we would actually use daily (nightly). At least for now, this was my attempt at reproducing real world useage. Although I turned on multiple lights for this first test, I did not turn on other appliances like the TV or computer/tablet chargers, etc. because these are really not connected as yet, nor have we installed or even decided on an invertor at this point. So, for what we will call “Test 1”, we really wanted to see how many days we could go with just the use of lights. Based on the hours we had at least two lights turned (1.6 amps per light), we estimate that we could probably have gone about 5 nights with adequate evening lighting, at which point the fully charged coach batteries would have dropped to about 70% state of charge.
With this information in hand, yesterday morning I climbed up on the roof of the Bounder and tilted the panels to 45 degrees. Then I positioned the motorhome for maximum morning sun directly on the panels. It was a sunny spring-like day with very high thin cirrus clouds. At 9:00 a.m. PST, I turned on the solar charger. Approximately 6 1/2 hours later, the batteries were 100% charged. Along the way, according to the TriMetric battery monitor I was “pulling” (is that the right word-maybe it’s “pushing”?) 350+ watts from the 400 watt panels, and amps were reading as high as 26.5, although consistently around 22.5. I’m still trying to get my head around all of this, but the bottom line is that the batteries were recharged in timely fashion.
Having spent part-time hours over the past 6 months to get to this “Test #1” stage, I’m thinking maybe it’s time for a Caveat and Editorial break in the action. My caveat is to reiterate for the reader that I am not an expert when it comes to anything solar or electrical. I’m one of these guys that decides to do something right or wrong, and then sets about researching the topic as much as possible so as to minimize the damage to come. Such has been the case with this project. I’ve used the internet to exhaustion. I’ve communicated with people I don’t even know. I’ve learned a lot, and I continue to learn.
One of the things I’ve learned is that you need to know your audience. What do I mean by that, you may ask? Well, for starters, if you are wanting to install solar on an RV, you should communicate with those that have actually installed, or have practical knowledge of solar applications in conjunction with RVs.
I’m not saying that you should ONLY research and communicate with RV solar folks. There’s a lot of information to be gained from ANYONE involved with the design and build of a solar system regardless of purpose. You should be a sponge, soaking up any and all information available. So, I’m not saying to ONLY focus on RV applications. But at some point, you are going to navigate into the RV solar camp because that’s where YOUR interest is if, in the end, you are going to have solar on an RV.
One of the topics that arises when it comes to ANY solar application has to do with whether to wire the panels in “parallel”, in “series”. At least in MY research, which is guaranteed to “maybe” be correct, many of the RV camp experts suggest “parallel” wiring. The primary reason for suggesting parallel wiring has to do with shade. When it comes to an RV, shade can occur in two ways It can occur as a result of where and how the RV is parked, and it can occur as a result of fixed objects located on the roof of an RV, including shade from the solar panels themselves.
So what does shade have to do with which way the panels are wired? Well, with parallel wiring shade only affects the panel that is in the shade. With series wiring, shade can affect ALL of the panels in the system, regardless of where or how much shade is falling on the panels.
Remember my mention of knowing your audience? As an example, one of the things I found out was that not all “solar” forums online are created equal. A forum may have a section that suggests “RV solar” discussions, but if the main purpose of the forum is in conjunction with “grid-tie” applications, meaning systems that are usually tied to the existing power grid with or without battery back-up, that is not necessarily where you will get advice that is directly relevant to RV solar. Such is the case with parallel vs. series wiring discussions.
Don’t get me wrong. There are genuine RV solar “experts” whose opinions I value, who might suggest that series wiring on an RV is the way to go. And for certain applications, they may be absolutely right. But in most cases that I have found, parallel is advised primarily for the reason that I have previously cited…shade.
Besides shade on an RV, another topic of heavy discussion is voltage drop. In its simplest sense, voltage drop is the difference between the voltage that is produced by the panels, AT THE PANELS, and the voltage that actually is received for use by the charge controller to charge the batteries.
To be continued…