After the electrical upgrade on our Jayco Greyhawk motorhome was complete I did not expect another so soon. We planned to travel several years before the next major change. However, by the end of our 2019/2020 snowbird trip, we replaced the Greyhawk with a brand new 2020 24RKS ORV travel trailer. This project was an order of magnitude greater in complexity than the last since it included both an inverter and rooftop solar. Regardless, I thoroughly enjoyed the work that was necessary to pull this off. We now have a sweet system that will serve us well for years to come!
After selling our motorhome on the road, I wanted an electrical system that facilitated future sale without expensive components left behind. Hi-tech gadgets add little value, especially on trade-in. Why not keep them for the next RV? We didn’t do badly on the sale of the Greyhawk; we kept our lithium batteries and charger module. However, the battery monitor, many feet of 2/0 cable, and other electrical components went with the sale. Either it was too difficult or removal would have left visible holes in the cabin area.
- [Goal] Conversion back to a stock system should be as simple as possible.
- [Requirement] No visible modifications inside the cabin (i.e. for controllers, monitors, or outlets).
Another requirement was that it must have an inverter. An inverter is a device that converts direct current (DC) from your battery bank to alternating current (AC). This comes into play when shore or generator power is unavailable or undesired. Even though both TVs are DC, we wanted AC power for laptop computers and other devices. This was not an issue on the Greyhawk because it came equipped with a respectable 1000W Magnum inverter. However, this time around we wanted a bit more power. It would have been nice to run the instant pot, coffee pot, hair dryer, or microwave without firing up the generator. Also, I didn’t like running extension cords because the inverter was only available at two outlets.
The last requirement was that it must have rooftop solar. We did not bother on the Greyhawk because it wasn’t clear it was necessary. Between the onboard generator and portable Zamp 200W solar panel we did OK. Based on anticipated power needs and no onboard generator this time around, we thought the extra solar charging would be nice. And, there is a convenience factor with onboard solar, its ready to charge all the time—even while driving. Also, where theft is a concern we can keep our expensive portable panel locked away.
Choosing Major Components
As mentioned previously, we kept our two lithium 100Ah Battleborn batteries we had installed in the Greyhawk. We recommend them for all the reasons discussed here. I felt two batteries were sufficient based on our months of use in the Greyhawk—and I didn’t want to spend $950 to buy another!
As discussed here, voltage is a poor indicator of State of Charge (SOC) for lithium because it varies little over the discharge cycle—a gauge that counts coulombs is needed. We purchased the same Victron BMV-712 battery monitor we used on the Greyhawk. I also purchased an optional temperature monitor cable to avoid charging when the batteries are too hot or cold.
A good starting point when choosing an inverter is to determine how you plan to wire it into your system. This can be as simple removable clips attached to your battery bank with devices plugged directly in the inverter. You could opt for a hard-wired installation and provide power to a small number of dedicated AC outlets. Or, if you wish to provide power to all your existing outlets, you could plug the inverter into the shore power cable. For this option do not forget to disconnect the converter each time so it doesn’t act as a bank depleting load. One of these choices might be right for you depending on your situation. However, drawbacks associated with the above alternatives steered us to an inverter/charger.
An inverter/charger is a dedicated whole-house inverter that supplies power to every load in an RV. When shore power is available an inverter/charger acts as a pass-through for AC and charges the batteries, eliminating the need for a converter (AC to DC conversion). Otherwise, when shore power or a generator is not used it acts as an inverter and converts DC supplied by the batteries to AC. An important feature of this type of inverter is its built-in automatic transfer switch. This switch prevents backfeeding of the AC supplied from the batteries through the inverter to shore power or a generator—something to be avoided.
I felt an inverter/charger would be easier to install than a standard inverter to dedicated outlets. Wiring is straightforward. First, disconnect shore power from the main breaker and run a cable to connect shore power to inverter AC input. Next, connect inverter AC output back through another cable to the main breaker. It’s recommended to install a breaker between shore power and the inverter. Don’t forget to disconnect your converter because it is no longer needed.
The next decision was size in terms of wattage. This choice is less definitive, but there are a few things to consider that may help clarify. First, examine the wattage requirements of the items you wish to run. Which of these will be ran simultaneously? Will the inverter you are considering be sufficient?
Another important factor is the size of your battery bank and it’s ability to supply current to the inverter. The rule-of-thumb for inverters (not a hard-and-fast rule) is to divide size in watts of the inverter by 10 to get the full load input current at 12 volts. Our batteries are rated at 100A continuous each or 200A total. Rearranging, the rule suggests an inverter size of 10 * 200A = 2000W.
Finally, consider how your RV is wired with regard to AC Power, either 30A or 50A. If 30A the system is designed to be driven by 30A * 120V = 3600W. If 50A, there are two 120V legs, so this entire system requires 2 * (50A * 120V) = 12,000W. Our trailer is 30A, but we do not plan to run the air conditioner from the inverter, so we can subtract those 1800 running watts. For our case we are looking at an 3600W – 1800W = 1800W system. Regardless of the size you choose, with an RV you must be mindful of concurrent loads to avoid an overload and/or damage to components.
With inverter type and a rough size in mind, I was ready to choose a manufacturer and model. Initial front runners were the AIMS 2500W Inverter/Charger, model PICOGLF25W12V120AL and the Victron Multiplus Compact 2000VA Inverter/Charger. For price ($568) and power rating the AIMS was hard to beat. At 2500W continuous and 7500W max, we would not be running this inverter at it’s maximum, which can only lengthen it’s lifespan. While I liked the price, I kept coming back to the Victron. Reviews I read for the AIMS indicated while customer service is good, quality, reliability, and features do not measure up to Victron.
The configurability of the Victron is superior. While the AIMS is limited to a few hardware settings, the Victron has a full suite of software settings. While this adds complexity, it also means there is a good chance it can be configured to play well with other devices in your system.
Another cool feature of the Victron is it’s hybrid PowerAssist technology. As demand requires, the batteries provide an extra boost of power. This is done to prevent an overload of a limited source such as a generator or shore power. For example, if you are connected to 15A shore power and you start the air conditioner, you can avoid tripping the breaker when the inverter current limit is set to 13A. This also means you can save money since the size requirement of the generator you buy is less.
My favorite feature of Victron devices is their Bluetooth support. While the inverter does require purchase of a separate Bluetooth dongle, the battery monitor and charge controller have it built-in. Via wireless connection to a smartphone or tablet, the VictronConnect App makes control and monitoring simple and painless. This feature was key in meeting our requirement of no visible modifications inside the cabin.
Solar Panels and Charge Controller
After taking measurements of available space on the roof, it appeared it would accommodate three or four 200W panels. This time around I wanted at least double the charge capability we had with our portable 200W panel. Considering the fixed nature of rooftop panels—you can’t easily move them to follow the sun—I felt that three 200W panels would meet our needs.
To see the benefit of the MPPT charge controller we planned to buy, the controller requires a relatively high photovoltaic (PV) voltage, via panel cell count and/or series connected panels. Since we planned to buy three panels a series connection was not an option—high cell count was critical. Common sizes for a 12V system are 36, 60, or 72 cells. Based on available space and panel size, I went with 60 cell panels (NPA200S-24H) from NewPowa. These are marketed as 24V panels and are rated at 34Vmp and 40.46Voc.
Decided on Victron components for both the inverter and battery monitor, it was a no-brainer to go the same route for the charge controller. I chose the Victron SmartSolar 100/50 model. This model is rated for 700W, which allows for a future upgrade to a fourth 200W panel for 800W total (slight overpaneling) and a 2S2P configuration. I don’t think this will be necessary.
Diagrams help to ferret out issues early and provide a means to capture design decisions. I recommend Draw IO because it’s easy to use and free.
The schematic below is a mix of components that were purchased for the upgrade and those pre-existing on the trailer.
For high current DC paths I chose 2/0 cable because it is rated to handle 200 amps for the lengths required, which is the maximum current my battery bank can source continuously. The catastrophic fuse is a 300 amp class T. These have an Amperage Interrupt Current (AIC) of nearly 20,000 amps and are incredibly fast acting when catastrophes (i.e. shorts) strike. Also, 300 amps is good size because it is within the rated ampacity of 2/0 cable, yet large enough to avoid nuisance blows of this expensive fuse.
Two bus bars are shown, one (red) positive and one (black) negative. The larger negative bus bar (650A) is connected to the chassis via 2/0 cable. It is connected in series with the battery monitor shunt and the negative terminal of the battery bank. All current that enters and leaves the bank is recorded by the shunt for high accuracy SOC measurement. The smaller positive bar (250A) is primarily a connection point for the positive load cables that had been connected to the stock battery bank.
Two subpanels were necessary. One holds the 30A breaker that is required between shore power and inverter AC input. The other is a Midnite Solar “baby box”, which controls and protects PV input and battery output of the solar charge controller, 40A and 60A breakers respectively.
The details of rooftop solar are not shown. The three solar panels purchased were connected in parallel through the existing Zamp Solar roof cap, with each panel protected by a 15A, 250V fuse. More on this later.
With electrical components chosen, I needed to figure out where and how I would install them. Leading options were under the bed or in the pass through storage; we went with the latter. Lusha wanted to keep space under the bed free for extra blankets and bedding, and I felt installation would require less time in and out of the trailer and on my knees, bending and reaching.
With component dimensions in hand, I took measurements inside the pass through. About 14″ inside the door compartment height drops from 28″ to 20″, where the bed runs across the space above. With inverter height also 20″ mounting options were limited. In the 20″ space the inverter would need to be mounted horizontally to provide its required 4″ spacing. Horizontal mounting is allowed, but for best cooling a vertical installation is recommended. I decided to mount vertically on a board centered in front of the door, adjacent to the main cutoff switch and battery monitor.
The other major decision was battery location. Placed side-to-side little space remains to get the inverter in and out of the compartment and allow access to battery terminals. For this reason I positioned them end-to-end. This battery layout sets a frame depth that allows for sufficient space between remaining components while minimizing wasted space.
Construction and Installation
Next came the scary part—cutting wood, drilling holes, and assembling component boards. Other than some wavy rip cuts (I don’t own a table saw) it went pretty well. I used machine screws, tee nuts, threaded inserts, and carriage bolts to assemble mount boards and attach major components. The benefit of machine over wood screws for much of the assembly was huge. This facilitated disassembly/reassembly and made it possible to do the lion’s share of wiring, enter configuration settings, and perform system tests in my garage prior to trailer installation.
The task I was most concerned about was no big deal—where to drill holes and run cable in the trailer. When we picked up the trailer from Thompson RV in Pendleton I spoke with Mark, their lead technician. For DC cables, he recommended a hole in the junction area, centered in the pass through storage near the front cap. For AC cables, he recommended a hole adjacent to the pass through door, behind the front steps, up through insulation next to the low point drains (below the bedroom sink), through the wall into the power center.
An important part of any electrical project is the quality of the connections. In addition to good crimper, I used Ideal Noalox Anti-Oxidant compound on all high current cable ends prior to crimping. I got the idea from this video by Ray at Love Your RV. Noalox literature says it promotes cooler operation and longer connection life, along with anti-seizing behavior, making it also a good choice for battery terminal and bus bar connections.
I also used two types of electrical connectors I hadn’t used before, ferrules and Wago nuts. Ferrules solve the problem of loose or brittle connections between screw terminals and stranded wire. These were used on solar charge controller, inverter, and breaker screw terminals. Wago nuts employ a snap lever and view window to ensure a solid connection. They are recommended in place of wire nuts for high vibration, stranded wire installations. These were used to make the AC to AC (10/3) cable connections. Note that Wago nuts do not work on ferrule ends, they only connect to bare wire.
I ended up with what I believe is a fantastic solar mounting system. When we received our first set of mount brackets I was thoroughly disappointed. Their tilt design was asymmetrical; one direction they were even but the other the arm required bending. I also had concerns about the small surface area of the feet. How would these hold up to wind? I sent them back and bought these brackets recommended by my friend Tom. They have a solid tilt design and large mount surface.
It was unclear how to securely mount these flat brackets across my arched trailer roof. Then, I watched this video by Travel New Trails. He used strut channel in a length-wise installation to provide the large flush mount surface I sought. Strut channel simplifies panel removal/replacement since they are attached via movable strut cone nuts, not directly to the roof. Channel thickness (13/16″) adds additional spacing between roof and panel to minimize heating losses. They also provide makeshift cable raceways and attach points to secure cable that otherwise would not exist. I purchased three 10′ lengths of channel and cut each in half, which was perfect for my three 65″ long solar panels. I attached the strut channel to the roof with butyl tape and a mix of #10 stainless steel sheet metal screws and the self-tapping screws that came with the mounting brackets. I covered the screws with a heavy coat of self-leveling Dicor.
Our ORV travel trailer came pre-wired for rooftop solar. The components used for pre-wiring by other manufacturers can be pretty lousy, but that of ORV isn’t bad. They install a ZAMP ZS-3B-CAP roof cap that includes three parallel ports and run 8 AWG cable down the front cap to the batteries. The intention of this layout is to connect the charge controller above the bed. For my system, I spliced the wires above the bed together to run directly to my controller in the pass through storage. I also bypassed the 30A short stop overload in the front electrical junction since I installed my own breakers. All that remained was to butt splice solar cable, SAE connectors, watertight fuse holders, and install 15A fuses.
This is not an exhaustive list of all purchased items. For example, fasteners are left out because that depends on your particular installation. Hope this information helps!
Note: I am not a solar expert or licensed electrician, use this information at your own risk. Research and plan your own system accordingly.
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