Category: Solar

Tomorrow’s Journey Solar Saga

We had hoped to install solar while we were on our winter trip to the southwest.  Sometimes things just don’t work out the way we dream. But the trip was fruitful in many ways – we met a great solar supplier and ended up with four Battle Born batteries at a great price from the Battle Born booth at Quartzite.  But, I’m getting ahead of myself.

Our basic philosophy on solar was to start with a modest build but design and install wherever possible with a maximum installation in mind.  The solar also needed to make sense with our power needs and the size of our battery bank.  Based on our expected needs and the fact we already had 400 amp-hours of lithium, we choose to install four 200Watt solar panels, but to design and install components based on an eight-panel, or 1600 watt system.  Our wire sizes, combiner box, and solar controller are all sized to carry that size of a system.

Installing more battery will require restructuring and/or expanding the battery bay.  Our current bay barely holds four batteries, but mostly because it uses a slide-out tray (which requires slack cables and a place for them to move) as well as a control panel that just plain wastes space.  It doesn’t make sense to double the solar but maintain the same battery, so any future expanse will be quite a project in itself.

We also chose to upgrade our inverter from a Magnum 2000 to a Victron Multi 3000.  This brings all of our major power devices under the same vendor and common management software as well as providing a bit more power and functionality. On our first winter trip, we had to be a bit more conscious of our AC current draw than we’d like to be. Also the Victron will work in Hybrid mode – monitoring the current and picking up the slack when needed.

Parts

We met Matt Dalley from ContinuousResourses.com under the big tent at Quartzite.  He was quite helpful.  While I am an electrical engineer, I had no experience in the world of RV solar and have more than a few things to learn.  Matt was very helpful, working through several renditions of my design and answering more than a few questions.  In the end, I ordered almost the entire system through him.  I am quite happy with all the products I received. One thing I must note though. When you order, you won’t get one big box with all your parts.  You will get a box every day or so, for a week or so, drop-shipped from various locations around the country.  In the end, this saves you money and I wasn’t in a big hurry anyway.

So, here is a list of parts:

• 4 x 200W Hitec solar panels
•  4 x panel mounting bracket kits (can be upgraded to tilt)
•  30 ft of 4/0 ultraflex battery cable and lugs (new wire from inverter to batteries)
• 30 ft of 4AWG UltraFlex battery cable and lugs (roof combiner to solar controller to inverter)
• 80 ft each of red and black, 10AWG PV wire for wiring panels (enough for 8 panels no matter where they are on the roof)
• 4 x MC4 2 in 1 branch connector (that I actually didn’t need, was thinking parallel at one point)
• Combiner box with 4 inputs and breakers for 8 panels (4 sets of 2 in series)
• Blue Sea Class T fuse block with cover (up to 400Amps) and 400 Amp fuse (for the eventual replacement of Battery catastrophic fuse)
• Victron Energy ve.direct and RJ45 UTP network cables and adapters
• Midnite Solar Baby Box and two breakers for switching panel inpu and Controller output.
• Blue Sea Battery Switch
• Victron Energy SmartSolar 150/100 Tr Charge controller with Bluetooth
• Victron Energy MK3-USB interface
• Victron Energy MultiPlus 12/3000/120-50 Inverter-charger 120V
• Victron Energy WiFi module (to connect Color Control to wifi)
• Victron Energy Color Control GX monitor
• Install kit – lots of misc parts.

Some explanation.  The 4/0 cable from the inverter to batteries was because the 2000 watt inverter in place was on the left side of the RV and batteries on the right.  While 2/0 cable that was in place is technically big enough for 3000 watts, it seemed like a good time to make sure the longer cable run was as good as it could be.  

I studied for some time as to where to put my combiner box, and thus the drop through the RV to the left rear bay where the controller would be installed.  After carefully considering the various walls and closets I might end up drilling through, I decided no drilling through the cabin was the solution. I chose to put the box at the rear of the RV and bring the wire down through the rear cap.  This made the future runs to solar panels mounted forward fairly long, but I ran through the calculations and the losses were minimal.  Better to make the series panel runs longer and the combiner to solar controller shorter as it carried the higher combined current that was easily handled by the 4AWG cable. 

Series or Parallel?

I waffled for some as to whether it would be better to put all my panels in parallel or some combination of series+parallel. With all the air conditioners, vents, etc. on the roof, something is going to be shaded any time the sun isn’t nearly overhead. If you shade one panel of two in series, you lose most of both. The other side of the argument though is if you put panels in series – there is more voltage for the controller to work with early and late in the day. I even considered running a pair of wires to each panel and doing the serial/parallel connections in my combiner box. In the end, I chose to serial two panels, each on the same side and parallel the groups. At least two panels should be making full power no matter where the sun is coming from. If I decide to change things later, it’s just a bit of wire, some connectors and/or 4 more panels.

A bit of relevant history. While we were out west on our first trip, we were clearly having a voltage problem – the inverter would complain about low voltage or simply drop out if we ran more than one appliance. This was a big part of the reason we went ahead with the Battle Born battery purchase at Quartzite.  The culprit, however, turned out to be a faulty catastrophic fuse connection mounted on the back of a switch control panel in the inverter power path.  The poor connection generated so much heat, it melted part of the panel including the inverter power switch which caused it to fail.  The fuse itself never failed – just the interconnect was resistive and thus got very hot. As a part of my solar plans, I intended to replace this entire panel, but because of time constraints, this part of the plan wasn’t executed.  It is still on my ToDo list. See the rest of this story on Youtube, Here.

Finally, we considered long and hard, on how to attach the panels to the roof.  So, this is a good time to segway into the FIRST install:

My Daughter and husband also bought 2 x 100-watt panels and an MPPT controller in Quartzite.  We were uncertain how they would use the panels – whether like a suitcase or on the roof.  It’s a rubber roof – so VHB tape was out.  The roof construction is basically rubber over 3/8ths (if that) plywood over styrofoam. Dropping screws into that combination doesn’t instill one with great confidence that the panels won’t become airborne. After some consideration, we decided to use butyl tape, well nuts and of course self-leveling sealant.  Since my arthritis had kicked into overtime, my duties were primarily supervising and/or critically important adjustments.  Thus, I made the mounting brackets out of angle aluminum (using jigsaw and drill press in the garage). I also drilled and tweaked the holes in the roof for the well nuts, but not a lot else.  We drilled the holes and carefully trimmed them so the well nuts would just fit.  We used ½” diameter, 1” long with ¼-20 brass inserts along with 1 ¼” stainless bolts. We attached the brackets to the solar panels, set them in place and marked the holes.  Then we moved the panels off, drilled the holes, pushed in the well nuts, laid a small amount of butyl tape around the hole.  Then the panels went back in place, were screwed down tight (two bolts per bracket), then self-leveling sealant on top.  They are very solid.  We configured the panels in series and taped down the solar wire with 2-inch segments of Eternabond tape.  A small roof entry box was mounted over the hole drilled in the front cap top to feed the main wires down to the solar controller and combination circuit braker and cutoff switch that we mounted inside the front storage.

Overall, it was a simple install.  Because the panels were going near the front of the trailer, we chose to use 6 brackets each.    We ran 4AWG cables from there to the batteries. Two hundred watts has been a good fit with the two 6V GC2 lead-acid batteries they have for storage.  It has been a couple of weeks now, and the panels keep up with most of their daily needs as long as they are parked in the sun.  They don’t have a big inverter, so they do run their generator when making a pot of coffee or when they need to run the Air Conditioner.

So back to the main event. I survived the mini-build, so we decided to go ahead and tackle the class A build.   This is central Illinois in the springtime, so we had to try to plan for a few days without major rain.  Of course, the forecast changes hourly, so we got chased indoors more than once.  

Our panels went on first. They came with four brackets each that hooked on and provided a pivot point that could be used with additional hardware (not supplied) to allow the panels to be tilted.  These brackets hooked over the panel and attached with a single bolt. I’m a “two is one and one is none” kind of guy, so we drilled and added a second bolt to each bracket. I scoped out 9 possible locations on the roof – we choose 8, then the four initial spots that would be toward the rear – but reserving the area at the very back for getting on/off the ladder and for the combiner box.  The box was bolted to the main cabin roof, but a 90 degree piece of PVC electrical conduit exited the back and entered the back cap for running wires down to the controller.  

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We installed the panels pretty much the same way as with the earlier install – except we used the provided VHB tape between the roof and brackets and stainless bolts into ½” by 1” well nuts with ¼-20 stainless bolts, two per bracket.  They aren’t going anywhere.  We ran the solar wire – setting up the two left panels in series and the two right in series, each pair to a breaker, connected in parallel before the 4AWG cables going down to the solar controller.  

Our left rear storage had the Magnum inverter, our power controller/EMS and our 50 Amp shore power cord already in it.  But there was plenty of room for the solar controller and the slightly larger Victron Inverter/Charger.  We mounted a piece of plywood on the inner wall, then the solar controller and the mini breaker box.  The cable from the panels went into the mini-breaker box, through a 60-amp breaker – out to the controller, then the output from the controller went into the mini-breaker box, through a 100-amp breaker and out to the main DC power cables that fed the Victron Multi.  The mini breaker box not only protects the input/output of the controller, but also allows me to isolate the controller from the panels and the batteries.

Then I double checked that all the power lines to/from the Magnum had corresponding connections on the Victron Multi (and were labled), took a deep breath, and swapped them out. And it all worked!  Once I remembered to flip on that tiny switch in front of the Victron Multi to the correct position..  

To back up a notch, we ran the 4/0 cables from the Victron (left rear storage) to the battery bay (right rear), pulling out the 2/0 that was there.  When I got up to pulling the old control panel – I realized I needed more hardware I didn’t have on hand, so we hooked up the 4/0 cables without changing the panel.  Here is one of those odd things you run into that makes you scratch your head (or bang it on the wall), wondering WHY they build RV’s this way. The ground cable from the inverter, ran to a bolt mounted on the battery bay wall.  From there a ground cable ran back to the top of the frame to another bolt (totally inaccessible).  From there a ground cable ran to the batteries.  Thus, I was not able to replace all of the 2/0 cable – at that time.  Most of it, however, is better than none of it. When I deal with the panel, I will make sure I have 4/0 though the entire path from battery to inverter.

Since the main inverter switch is actually in the right-side battery bay, an unintended consequence of this particular install was that the Solar only charges the batteries when the inverter switch is on.  Not too big a deal as when we are using the RV, it is always on.  When in storage, it might be a different situation, so likely I will move the Inverter switch to the left storage bay, or reinstall the 2/0 positive cable just for the solar controller to the battery (my preferred solution).  This last solution would also bypass the main battery switch, so I could shut off power to the RV, but still keep the batteries charged.

So, we’ve only had a few days of actual use – boondocking.  On a mostly sunny day, it keeps up with our use (refrigerator, coffee maker, TV, microwave, two laptops running much of the day, etc).  Since leaving home (a week now), we’ve only run the generator once for about an hour. In South Dakota it is running 600+ watts several hours of the day and we hit over 800 once.  I’m quite happy with it.  I’d be happier of course, with more battery and more solar so we had a several day reserve, but that won’t happen for a while.

Futures?

Replacing the battery switch/breaker panel and catastrophic fuses.

Rerouting some of the AC power. Right now, the AC leg that goes through the inverter only connects to the various plugs and appliances in the coach. The air conditioners and fireplace, for example, come off the EMS/Gen/Shore switch BEFORE the inverter. In theory, I could run one air conditioner off my inverter and batteries by using the inverter to boost power from a low current shore power source, But only by rerouting AC power for the air conditioner THROUGH the inverter. This will probably wait until we upgrade the system to more battery and more panels and I would install a switch so the air conditioner could be powered via either path. .

The only special tool I purchased for this install was a hydraulic crimper. I purchased this one: https://amzn.to/2FbUiXc on Amazon for $45.99.

Appropriately size well nuts can be hard to find. I scrounged through every hardware store in town, to find enough. While local HW stores would carry them, they often only had half a dozen or so of each size in stock. Make sure you get the ones with the thin shoulders so your brackets sit on the roof. The well nuts, or expansion nuts, as some places call them, need to be longer than the plywood/fiberglass on the roof – thus I used 1 inch long. I had some 1/2 inch versions and they didn’t hold properly in tests.

Feel free to ask any questions, here or over on youtube. Get to know use here on Youtube and please subscribe.

Postscript. I continue to be happy with the system. It won’t keep up with our needs when we are shaded as we are this week in Glacier, but it is working as designed. Its cool that as long as I have cell, I can connect back and see how the entire system is doing.