Series: RV Solar
In this article...
At the end of Part 1, we ended with a plan: until we had a better idea of how much solar power we needed, we'd start with a portable panel.
Why a portable panel?
As with most things, there are pros and cons to portable solar panels - sometimes known as deployable panels.
In case you haven't seen these before, the most common style for RVers is the so-called Folding Solar Suitcase - typically a rigid glass solar panel that unfolds from its neoprene case to form a self-supporting solar panel. This is the style we chose to start with.
These are great for several reasons. They pack down relatively small, they're not too heavy to carry, and they're quick to set up. Because they have a stand built-in, it's easy to position them in the sun and turn them once every couple hours so they're always pointed directly at the sun. Solar panels need to be in the sun to work (even partial shade will significantly reduce the output of a panel), so for rooftop panels you need to park your RV in the sun - whereas with a portable panel, you can keep the RV cooler by parking in the shade, and put the portable solar panel out in the sun.
They're not without their downsides either though. First, they're not cheap - often around twice the price of an similarly size flat panel to mount on the roof. You're really paying for a hinge, stand and neoprene case - as well as the simple setup.
Also, although they're simple to set up and operate, they're not zero-effort. You still do need to set them up and pack them away every time you move, and turning them to face the sun during the day is essential to maximize their output.
In balance, they're a great option for people who don't need too much power - just enough to charge phones and keep the RV batteries topped up enough for lights and the water pump, for example - and don't want to invest in a permanent installation.
Although we knew we wanted rooftop solar long term, we decided to start with a portable panel - purely for the ease of getting started.
Renogy 100W Folding Panel
We chose to go with the Renogy 100W 12V Monocrystalline Off Grid Portable Foldable 2ps 50W Solar Panel Suitcase with Built-In Kickstand. Wow, what a mouthful! Let's break that down.
This panel is made by a company called Renogy. Like with anything, some brands are better than others, but Renogy consistently performs well in reviews and is far better priced than some of its competitors. We were generally happy with the build quality (the stand broke on ours, but we spoke with Renogy in person at Quartzsite, AZ, and the stand has been improved on the newer versions). In our experience, both in our own research and seeing other people's panels, more expensive panels aren't necessarily better.
Certainly, we've seen nothing to suggest that a cheap 100W panel is going to produce less power than an expensive 100W panel - we'll discuss power output more in the next section.
These panels are known as 12V panels. Personally, I hate that term. What it means is that it's designed to work with a 12V system to charge a 12V battery and power 12V appliances. It does not mean the output of the panel is 12V! The output on this panel is actually more like 18V (fairly standard for a 100W panel).
We chose to buy the version of this panel without the integrated charge controller. If you connect this directly to your RV's 12V system you will damage your batteries, devices and more - do not do it!
Renogy also sells an identical panel that has an integrated charge controller - this is designed to be connected directly to your batteries, and is probably the version you'll want if you don't already have a solar charge controller.
This panel is monocrystalline - as opposed to polycrystalline. Simplifying things slightly, polycrystalline panels are slightly easier to produce so they tend to be cheaper, whereas monocrystalline panels are slightly smaller for a given power output. I'd recommend monocrystalline, particularly for portable panels, to keep size to a minimum.
Finally, this is an "Off Grid Folding Portable 2pcs 50W Suitcase with Built-In Kickstand". Put simply, it means that the 100W panel is made up of two 50W panels connected by a hinge. And when you unfold them, there's a built-in kickstand to support the panel.
We chose to buy the panel from Amazon as we wanted the free delivery. We had it shipped to our mailbox at Escapees in Livingston, TX so we could collect it before we headed off to the Albuquerque International Balloon Fiesta.
When a panel claims to be 100W, will you really get 100W?
The power rating is a peak power rating - essentially this means in direct, full sunlight on a sunny summer day, that's the most the panel can produce. But what about in October in Albuquerque, NM?
Impressively, we did see 100W of output from it! And actually, over the next few months, as long as the panel was pointed directly at the sun, we often saw very good output from it.
Over the course of a typical sunny day, you will see production climb until solar noon, before dropping again in the afternoon. As a general rule, you'll get the most production from your solar panels between 11am and 1pm.
The chart below shows how much power we were consuming or generating on December 18th, 2018 - just 3 days before the shortest day of the year! You can see that overnight, our background draw is around 35W (the spikes up to ~100W are our furnace kicking in). During the day time, the curve goes negative - we were producing more solar power than we were using - and it peaks at -52W. If we assume the only power being used was the background draw (35W), then we were producing 87W. Not bad for a 100W panel in mid-December! The chart also nicely shows the typical production curve during the day - low in the morning, picking up by lunchtime, and dropping off in the afternoon.
Because of the way solar panels work, even a tiny amount of shade can significantly reduce the output of the panel - almost to zero. Something as small as the shadow from a blade of grass in one corner has a big effect, so be mindful of where you're positioning the panel.
REDARC Solar Charge Controller
By the time we were working on installing solar, we had already installed the REDARC BCDC1240D DC to DC charger.
If you haven't already done so, check out our review of the REDARC charger, because it's a great device. As well as letting us charge our RV batteries from our truck at much higher power than the 7-pin connector, it also has a built-in MPPT solar charge controller.
By using this, we could save some money and buy the solar panel without a built-in solar charge controller, rather than the more expensive panel with the built-in charge controller.
The REDARC charger can handle up to 600W of solar power, meaning that if we wanted to have multiple portable panels in the future, we would save money on each panel as we wouldn't need a separate charge controller on every panel.
Although I wouldn't recommend buying the REDARC DC to DC charger just to use as a solar charge controller for a portable solar panel, I do recommend it for truck charging and since we already had it, it made sense to use it for this too.
Our Outdoors RV 21RBS, like many, came prewired for solar. This means there is a small socket on the side of our RV for connecting to a solar panel. Specifically, it came prewired for Zamp Solar. Zamp Solar is a company based in Bend, OR that makes solar products - including solar panels and more.
There are two common connectors used in solar panels - MC4 (Multi-Contact 4mm) and SAE (named after the Society of Automotive Engineers). Renogy panels use the MC4 connectors, but our RV's socket is an SAE connector.
As the name suggests, the original use of SAE connectors was automotive applications - specifically for applying a maintenance charge to a vehicle battery (it's still commonly used today on trickle charges for motorcycles and ATVs). The connector itself has two terminals - one exposed and one shrouded. In its original form, the exposed terminal on the battery side was negative - so that if there was a short between the exposed terminal and the vehicle, no short would occur. Although there is a chance of accidentally short circuiting the battery charger, this is far less likely and easily mitigated with a protection circuit in the charger itself.
However, Zamp reverses this polarity compared to the rest of the industry - the exposed terminal on the RV socket is positive. Zamp claims they do this so that is for safety, so there is less chance of receiving an electric shock from the solar panel. A cynic may choose to believe they do this so that their wiring is somewhat proprietary; and hence RV owners are inclined to buy a Zamp solar panel for compatibility.
The Zamp panels are significantly more expensive than many of their competitors, one of the reasons we chose to buy a Renogy panel.
So how do we convert from Renogy's MC4 connectors to Zamp's reversed SAE?
Actually very easily!
These products just simply press-fit onto the solar panel wires - no tools necessary.
We also chose to use a Renogy 30ft Extension Cable, but bear in mind this only has MC4 connectors on one end, so you'll need to either crimp on your own MC4 connectors, or cut the existing connectors off your panel and splice this extension cable in (which is what we did).
So assuming you have a Renogy solar panel with a built-in charge controller, you can connect it via an optional extension cable, through the MC4 to SAE adapter and SAE polarity reverser, and then plug it straight into the solar port on the side of your RV.
The SAE port on the side of the RV is connected directly to your RV's batteries.
Very easy; very simple!
If you've been reading closely though, you'll recall that we wanted to use the MPPT solar charging capability of our REDARC DC to DC charger. That means we rewired the solar port on the side of our RV to connect to the MPPT input side of the REDARC charger, rather than directly to the batteries.
This was very easy to do. On our RV, the wire from the side port connected onto the 12V wiring system in the front electrical access bay just behind the tongue of our trailer. I disconnected it from there, and then spliced it into a cable which I ran through to the yellow wire on the REDARC charger, located under our bed along with the batteries and inverter.
When we did this, we considered reversing the polarity of the wires inside the solar port on the side of the RV. This would remove the need for the SAE polarity reverser. However, we decided on balance not to do this.
Purely for the sake of any future owner of our RV. The Zamp polarity is ubiquitous on Outdoors RVs, so to avoid any confusion, we left it wired with the same polarity as it had when it came from the factory.
We've talked about SAE and MC4 connectors already, but I want to introduce you to a third. Let me tell you why....
At the Xscapers New Year's Eve event in December 2018, our RV was parked on some public land in Quartzsite, AZ along with everyone else. Our solar panel was out, the skies were clear and we were producing power. Perfect.
Until, it wasn't. I woke up on New Year's Day to find that despite the sunny weather, we had no solar power coming in. 0W. Uh-oh.
I went outside to investigate.
The SAE plug from our solar panel was badly bent, and hanging out of the socket on our RV. With the SAE reverser and MC4 connectors, it's quite a large plug. It looked like some drunken idiot had knocked it overnight.
Now, in all likelihood, that drunken idiot was me. There was no reason for anyone else to have walked there, and New Year's Eve had been a, erm, merry night! I did a temporary repair to get power restored, but it was clear we needed something more resilient - a stronger connector.
If you've read our guide about wiring up the REDARC charger, you'll know I'm a big fan of the Anderson connectors. These are strong DC connectors, easy to use and capable of carrying plenty of current. So I ordered a pair of Anderson SB50 connectors from Amazon.
Adventurous Tip: Anderson connectors will only mate with connectors of the same color - in this case, grey. Also make sure you buy some with lugs included - the link above includes four 10AWG lugs.
I've had great success with TEMCo wire, so I ordered 100ft of TEMCo 10AWG wire as well - I knew I'd need more for installing the rooftop panels eventually. They also sell it in smaller lengths, including 5ft, 10ft, 25ft and 50ft.
I chose to mount the Anderson SB50 connector on the tongue of the RV, running the wire into the front electrical access bay and splicing it in where the side port had previously been connected. I used some leftover split wire loom and cable ties to secure the wire and connector in place.
The end result is a much strong connection for the portable solar panel, ensuring it is safe from drunken revelry in future!
Sadly, the portability of a deployable solar panel is as much a weakness as it is a strength. I speak from a position of some authority on this, as we had ours stolen.
As if to reinforce our supposition that we're safer boondocking than we are in a campground, our Renogy 100W portable solar panel was stolen while in an RV park - specifically, Emma Wood State Beach near Ventura, CA.
It was my fault. There were numerous notices and warnings at the entrance that thieves are prolific in the area, and sure enough, we became a statistic.
I was camping there alone while Diana was at a dance tournament in nearby Los Angeles. I had the portable panel deployed to soak up as many California sun rays as possible. The panel was plugged into our Anderson connector and, as always, cable locked to the trailer with our RV's integral ToyLok.
I awoke the next morning to find both the electrical wires and the cable lock had been cut. The panel was gone, and I hadn't heard a thing.
There was nothing to do but go through the motions. I reported the theft to the State Park Ranger, who gave me an incident report number and little confidence that I would ever see the panel again. I removed the now-ruined ToyLok from my trailer - its pathetic attempt at securing the panel merely reinforcing its role as a "toy lock"; in other words, not a real lock.
My only consolation was that they had stolen a panel with no integrated charge controller, so whoever plugs that in would probably fry their 12V system with up to 20V coming off the panel. Karma would have to serve justice for me.
But I hope our loss can serve as a lesson for others. Unless your panel is well secured (for example, with the Kryptonite New York Fahgettaboudit Chain and New York Disc Lock that we use to secure our bikes), locked away inside your vehicle or RV, be aware that it may be a tempting target for opportunistic thieves.
We bought a portable solar panel for the same reason many others do - it's the quickest and easiest way to get started with solar. Although (as we knew from the outset), that the panel wouldn't provide all the power we needed, it consistently produced strong output, often achieving its rated maximum. The ability to position the panel in direct sun, and turn it during the day helped make the most of the low winter sun.
But these same features are also the weaknesses of the system compared to a permanently mounted roof install. Every time we moved, we had to pack it away and then redeploy it at the new location - not a big chore, but it added a few minutes to the process on each side. Similarly, its portability ultimately led to its untimely departure when the lock was cut and it was stolen.
On balance, there are plenty of situations in which a portable panel is a great option. If you're a part-time RVer with modest electrical demands, a portable panel may be all you need to keep your batteries topped up. Likewise, if you prefer to camp in shaded spots, the ability to deploy the panel in the sun, a distance away from your RV can be invaluable.
During the 6 months or so that we had the portable panel, we learned enough to know that we wanted to install solar panels on the roof, and to gauge how much we thought we needed. Stay tuned for Part 3, where we're going to be installing roof-top panels and a new solar charge controller in our RV!
Let us know in the comments if you have a portable solar panel, and why you chose to do that rather than mounting panels on the roof.