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All summer long, it's been working really well for us. We've been happily running everything we want inside the RV - lights, laptops, TV, furnace and so on.
But during the fall, and especially as we've moved into winter, we've started to struggle a little. Cloudy days happen more often, and when they do, our solar panels aren't enough to charge our batteries up again.
And even on sunny days, with daylight hours getting shorter and the sun lower in the sky, we've only been able to recover an extra 5-10% each day - it can take several sunny days to recover from one cloudy day.
In other words, we're starting to struggle.
Couple that with increased electrical demands during winter (lights and furnace in particular), and it's clear we need more power!
In case you were wondering, how did we manage last year with just a portable 100W panel and nothing else? Well, we were typically only dry camping (or boondocking) for 3-5 days at a time before heading to an RV park to recharge. Plus, since then our electrical demands have increased - things like our AeroGarden - and they're not things we want to give up!
Why a portable panel?
When we designed our roof-top solar installation, we laid out it with space for 10 panels to give us a total of 1,000W. Since we only have 600W up there now, we could add another 4 panels. There are a couple of reasons we chose not to do this:
- The layout of our roof means tilting the panels isn't really an option, and flat panels aren't as effective with the low winter sun (which is our problem in the first place). We're fine in summer, so it's just winter we're trying to accommodate better.
- Whilst the placement of the first 6 panels was easy, the next 4 is a little trickier. There's a risk of them being shaded by the AC unit, plus it'll make getting up on the roof harder.
- Our existing Victron MPPT 100/50 solar charge controller would be maxed out by 800W of panels, so we'd either need to upgrade or be prepared for it to dump the extra power in summer.
Since our REDARC BCDC1240D truck charger has an MPPT input wired up to an Anderson connector on the tongue of our trailer, we decided to go with a portable panel without a charge controller built-in. We can easily deploy this when we need it, and being tiltable we can make the most of the low winter sun.
They cost how much?!
As soon as I started shopping online for suitcase panels, I got some serious sticker shock - those things are expensive! We were naive when we bought our 100W panel so I didn't really know how much these things should cost, but I know a little more now.
A suitcase panel is essentially just two rigid panels hinged together and supported by an integrated stand that folds out. They usually have a clasp to lock them shut and come supplied with a neoprene-type case to keep them in.
But compared to buying rigid panels, the suitcase panels cost almost twice the price per Watt! There's no way I'm paying $$$ for a hinge, stand and a case - time to DIY!
The first question is: how big should the panels be? The reality is that whether I'm building a 50W panel or a 200W panel, the time taken to build it, the cost of the stand, and the effort to deploy it is going to be about the same. So it made sense for us to go bigger rather than smaller - after all, we want to maximize the little winter sun we see!
After taking some measurements, I realized that the Renogy 100W panels we have on the roof are about the perfect width to slide into our front storage bay. Since we don't intend on using the portable panel all the time, I can potentially build a hanging rack to store them on when not in use.
So I chose to build a 200W suitcase panel using two 100W Renogy panels. These panels match the ones on our roof, so I can always put them up there later if we choose to. But you can you use any panels you like for this - the general approach is the same.
Our plan keeps it simple - two 100W panels attached with a hinge and supported by a sturdy stand. I don't plan to add a handle (it just makes it easier to steal) and we don't need the case.
As for the stand, I spent a lot of time carefully examining photos of commercial suitcase panels online. Having owned a Renogy 100W portable panel before, we weren't impressed with the quality of the stand - by comparison, Zamp's stand looks much sturdier.
After a lot of research, it appears that Zamp uses casement hinges on their panel. I found some on Amazon that extended enough for this application and that I felt would be sturdy enough.
Time to get building and save some $$$.
Parts & Tools
When we started this project, we happened to be staying at an RV park that allowed us to have Amazon deliveries shipped directly to the park. For a lot of the hardware though, I chose to go into a local Home Depot and pick things out in person - much easier to visualize! I added a few extra elements later, and picked those up from a True Value hardware store.
Item | Quantity ---|--- 100W Renogy Solar Panel (Compact Design) | 2 Ranbb 2pcs 12-inch Stainless Steel Long Side Hung Casement Hinges | 2 48 x 1 x 1/8-inch Angle Aluminum | 3 Hobby Hinges (2-pack) | 2 #12-24 x 5/8-inch Stainless Steel Machine Screws (3-pack) | 12 #12-24 Stainless Steel Machine Screw Nuts (5-pack) | 8 | 36 x 1/2 x 1/2-inch Square Steel Tube | 1 36 x 3/8-inch Threaded Zinc Rod | 1 3/8-inch Nylon Lock Nut | 4 3/8-inch Washer | 4 Anderson SB50 Grey Connector with 10ga Terminals | 1
I tried to keep the build really simple insofar as tools are concerned. I was easily able to cut the metal with a hacksaw. I bought a nice new titanium 1/4" drill bit for my Dewalt Drill and found using a center punch for the holes really helped.
You'll also want a Philips head screwdriver and a socket or wrench to fit the nuts. Some of the spots are really tight so we had to play around to get everything mounted, but we managed it all.
I used my 16-ton hydraulic crimper to crimp the Anderson connector on, although it's not ideal as the terminals are a little small for the dies. I managed to get a good crimp though. I used my heat gun and some adhesive heat shrink tubing for the connections, but electrical tape would work too.
I want to give a huge shout-out to Phil from You, Me & the RV for helping with the build. We were camping with them at the time and Phil gave up several hours to help me on this project. The build wasn't hard, but an extra pair of hands and eyes really helped - thanks Phil!
Constructing the stands
Before making any cuts, I sketched out what I wanted the stand to look like - in particular, the angle. Although it's important to consider the angle of the winter sun, my biggest concern was making sure the panels would be sturdy!
To minimize the number of cuts, I chose to use 24" stand legs (i.e. just cutting the 48" pieces in half) and then work out where to mount them based on the angle I wanted. I chose an angle of about 40º to the horizontal which I felt would be nice and stable.
I was very pleasantly surprised when the casement hinges arrived from Amazon - these things are sturdy! We used a 12" piece of the angle aluminum (just the 48" piece cut into 4) to mount the hinges on the sides of the panels. If you use different panels then you may need to find a different way to mount the hinges depending on how the frame is constructed.
Because we were going to hinge the panels, we deliberately drilled the holes on the second panel in slightly different locations so that the screw heads wouldn't align when the panels were closed.
We took our time to align the holes as precisely as possible so the stands would be straight and level - it worked out great.
Reenforcing the stands
With 4 individual legs securely bolted to the panels, we could probably have left it there. But I wanted to make it even more stable. Without the ability to weld, our options were limited, so we chose to install a piece of threaded rod inside a square steel tube between the two legs on each panel.
I cut the square steel tube to the exact length it needed to be (15-1/4 inch for our panels) and cut the threaded rod 1-1/4" longer. That was just the right length to attach it at either end with a washer and nylon lock nut. The threaded rod should be as short as possible so it doesn't interfere with the hinge operation.
This added a LOT of rigidity to the stand - having now deployed it several times, including in windy conditions, I am very confident in how sturdy it is! Not just that, but the bar makes it easy to open and close both legs at once.
Since the square tube is made of steel, I spray painted it with black paint (bedliner, actually) to protect it from the elements. Functional and looks cool!
Installing the hinges
With the panels face down on the floor (lying on the cardboard boxes to protect them), we aligned them and clamped them together. Although we probably could have managed with just 2 hinges, for extra strength we went with 4 - spaced along the length of the panel.
The design of our hinges meant we could only install 2 screws on one side and 1 on the other, else the screw heads would hit each other and the panels wouldn't close properly. The panels open and close very smoothly, and they're definitely secure!
Wiring it up
The MPPT input on our REDARC BCDC1240D has a maximum voltage of 32V, which meant I had to wire out panels in parallel rather than series. Fortunately, I was easily able to crimp the two positive wires from each panel (after cutting off the MC4 connectors) into a single terminal for the Anderson connector - and the same on the negative side.
I used liberal amounts of adhesive heat shrink tubing and electrical tape to wrap it all up and keep it tidy.
We have a fuse on the Anderson connector on the trailer, but make sure to consider how your panel is going to be fused.
As I sit here writing this blog post, the panel is deployed outside to help get us through some cloudy days while we boondock. Because the REDARC charger doesn't integrate with the Victron system, it's effect is to reduce our DC load.
The screenshot below shows our current solar production just after noon on a late November day - helped by some cloud effect for sure! While we're pulling in 430W from the rooftop solar, our DC power is at -102W. Since our actual DC load is around 100W, that means we're getting right around 200W out of our portable panel - not bad at all!
The total cost of all the parts was under $360 (excluding tax and shipping). Comparable commercial panels cost anywhere from $500 up to over $750 depending on the manufacturer. Building our own panel only took a few hours, required minimal tools, and the end result is something that seems much sturdier than the ones you can buy.
So if you're thinking about adding a portable panel to your RV setup, then consider building your own and you could save a lot of money!