Sunshine to Acid

With the sunshine collector mounted on the roof, it was time to run some copper towards the battery. Many systems default to 12 gauge wire from the panels - some even come with the thinner 14 gauge but this is a case where bigger is better. I used 10 gauge to reduce the voltage loss from the panel to the controller. I'd suggest using a voltage drop calculator to determine what size wire to use.

I also elected to replace the default MC4 connectors with sealed, shrink type, crimp connectors to reduce the chance of a high resistance connection.

The red shrink tubing was used on both ends of the positive lead to make it easy to identify.

I installed a fuse near the panel, and clamped the cables on each end of the fuse holder so that there was no possibility of tension on the connectors.

I've seen many installations where the MC4 type cable was run across the roof in the open. It is usually ultra-violet resistant, but I wasn't happy with the idea of black wires running across our white roof so I used plastic flex conduit and a plastic junction box. I used 1/2 inch conduit which very nearly got me in trouble. The cables could barely slip through the adapter between the conduit and the box. Next time 3/4" for me.

The plan was to drop the cable through the roof into the same closet where I ran the cell phone antenna. The easiest way to locate the right spot was to back drill from the closet.

With the spot marked, I drilled out the hole with a 3/4" forstner bit from the top.

This idea didn't work. I put VHB tape on the junction box to hold it in place AND a bead of 5200 to form the seal. There was enough 5200 that it spread over the VHB so that it wouldn't stick. Next time I'll just use 5200 around the hole in the box and seal the perimeter AFTER I stick the box to the roof.

All's well that ends well. The box and conduit in place. There's an extra loop of cable in the junction box in case we decide to add an additional 50 watt panel so that we can actually use the junction box as a junction box instead of just a pass through.

The cable from the panel was routed down the corner of the closet

and the controller was mounted to the wall in the closet. For now we're using the inexpensive Renogy 30 watt controller but it will be replaced someday with Bogart Engineering's SC-2030 controller. The SC-2030 is adjustable and can be set to voltages recommended by battery manufacturers instead of the significantly lower set points built into most controllers (including the Renogy.)

The 8 gauge wires from the controller were routed down through the floor of the closet and the corner of the toe-kick space. I had to reduce the wire count in the cables where they attached to the controller since it was physically limited to 10 gauge wires at the connectors.

I used shrink tubing for an extra layer of protection in a couple areas and zip tied the wires to the existing bundle every 4 to 6 inches.

I installed a fuse on the positive lead and then connected both leads from the controller to the battery pack.

The biggest challenge for the wiring was finding connectors locally that could handle the 8 gauge wire.

It's all hooked up, and the controller indicates power from the solar panel when the lights are on in the garage. Next trick is to actually go camping and see how it does. I'm off to Quartzsite for solar testing.

Notes:

1. The Renogy controller is positive ground which I didn't catch in the description until I had the controller in hand. It doesn't matter in our fiberglass trailer, but could be a deal breaker in a metallic structure.
2. Until we install a TriMetric battery monitor we'll not have accurate data regarding how much power the installation is actually producing, but we will be able to observe the impact in general terms by the voltage (or specific gravity of the acid) in our batteries.

Gluing a Panel on an Egg

Since our refrigerator is on the street side, our preferred camping orientation is with the door side facing south. While we're not currently using the attach blocks for the canoe rack, I don't want to block them in case we need to use them at some time. That leaves us with about six lineal feet parallel to the awning case, but with the need to deal with the tapering trolley tunnel and the curve of the structure.

AM Solar makes a wonderful set of stainless steel mounts which will deal with roof curvature, but because of limited space I need to cantilever the hinge points for the panel so their solution won't work for us. I started by picking out hardware for the panel pivot and tilt bar pivot and then snagged the last two hand knobs the local Ace Hardware had with 1 1/2" long threaded shafts.

I picked up some 1" x 2" aluminum angle, 1" x 1" aluminum angle, and some 2" aluminum strap from the offcuts bin at one of the local metal sources. It will magically become the custom panel mounts.

There's nothing about a Scamp body that is straight, square, or plumb. I decided to use the awning case as my baseline and work from there. I set one piece of angle at the forward most possible point and then started mocking up the rear mount to match those angles.

I haven't done any aircraft maintenance for over 20 years and haven't used my rivet gun for over 15 years but found that the skills don't totally disappear. The mount feet were riveted to the bracket with countersunk rivet heads on the inside of the mount. It's not show quality, but it will hold together.

I used some 1/4" high density polyethylene (HDPE) left over from the cutting board / sink cover project as spacers and bearing material for the attach points. The spacer creates space for stowage of the tilt brace.

First bracket painted and assembled. The tilt brace has some foam on both sides to keep it from rattling when sandwiched in the closed position.

With the first bracket temporarily in position, I positioned the second angle and clamped the mount feet in position to match the same angle as the first mount.

In theory, it should be a mirror image of the first bracket, but the tapered trolley tunnel clearly impacted the length of the inboard mounting foot.

I wanted to use a nutplate to receive the hand knobs, but the knob stud had 5/16-18 threads and nutplates aren't available with coarse threads so I made my own from some pieces of maple and appropriately sized tee nuts

I added a shallow dado to allow for the tee nut to set flush and then put a coat of varnish on the wood to provide for some degree of water proofing.

The block and tee nut combination functions like the nutplate that I wanted. It's hidden inside the panel frame and protected from most weather.

It's held in place by a pair of stainless steel flush head screws.

With the brackets attached to the panel, I was able to set the assembly in position and mark where each foot would be. The marks were essential because the wax needed to be removed from the fiberglass at those points.

The mount feet were cleaned and then 3M Very High Bond (VHB) double faced tape was applied to the feet.

After the assembly was carefully set in place (the VHB will stick as soon as it touches), I sealed around the feet with 3M 5200. Standard 5200 takes 7 days to cure, but is the suspenders part of my belt and suspenders attachment system. Either the 5200 or the VHB should be adequate. If more assurance is needed, the feet could be riveted to the Scamp but I don't want to make more holes than necessary.

Notes:

1. I started with stainless steel hardware for the pivots, but stainless on stainless is known for galling problems. I was able to install and remove twice, but the third time required cutting two of the machine screws so I replaced the pivot hardware with steel that will have to be painted.
2. The location is not optimal since the panel could be shaded by the air conditioner if the trailer is not positioned with the door substantially to the south, but it was the only location we had that would allow for enough access to tilt the panel. We'll use the 5' ladder we carry to access this panel for tilting.
3. We have just enough space forward of this panel to install an additional 50 watt panel if necessary. We could install 100 watts on the loft, forward of the escape hatch, but it would be too high to access for manual tilting.
4. Fast cure 3M 5200 would have been nice, but I have a local source for the standard version so that's what I used.
5. Other RV structures (rubber roof, aluminum, etc.) would likely need a different attachment solution.

Solar Musing

I've been considering solar for the Scamp for the past three years. It would be nice if there was a magic bullet, a 'one size fits all' solution. Some vendors would suggest that's exactly the case and they'll sell a standard package. Works well if you have the mythical 'standard' RV with the even more mythical 'standard' power demands. A little study quickly showed there weren't any magic answers.

There are some very worthwhile resources that are specifically oriented to RV solar. But even those resources don't always agree. If you're thinking about solar, I'd suggest you start by carefully reading HandyBob's Blog, the section of Jack Mayer's website about RV Electrical & Solar, and the RV Solar Education section on AM Solar's website.  Both Technomadia and Wheeling It have done excellent posts about their massive (at least from our perspective) installations and their selection process. They both used AM Solar for their installations.

Before our first year with the Scamp was complete, I'd installed a Doc Wattson meter to track our 12 volt power utilization. This meter can be installed to show power usage or wired in reverse to show power input to the battery, but it can't do both. Eventually, I'll replace it with a more expensive and much more capable TriMetric 2030 Battery Monitor system. A way to accurately measure, monitor, and understand your power consumption is the first step towards sizing an appropriate system.

When boondocking, we don't have any essential requirement for 110 volt a.c. We do carry a 100 watt portable inverter to use with the camera battery charger but everything else is 12 volt or propane powered. We don't have a TV, microwave, or coffee maker to power so we don't have to account for the cost or power consumption of an large inverter. We converted to all LED lighting which is a major power savings and now average 25 amp/hr use each day. We never go over 30 amp/hr, even with extensive computer use and/or daytime heater use. Our power demands are listed on the Scamp 19 page at the top of the blog and are higher in the winter when we're using the furnace than in the summer.

We swapped out the standard Scamp battery for a pair of 6 volt golf cart batteries about 3 years ago, giving us 205 rated amp hours of battery or about 100 amps of usable battery capacity. Our batteries are Interstate brand, simply because that was what Costco carried at the time. We can go four to five days before needed to charge the batteries, but I don't like to haul and mess with a generator to charge the batteries.

With adequate battery and accurate power demand history, it was time to start thinking about options to create our own power. For a couple years we hauled a Honda generator and would fire it up every four or five days to power a high capacity battery charger. The generator didn't get much use, and it was more hassle to haul and store and keep fresh gas in it than I wanted. Of course, if I were based in the southeast where high temperatures and humidity make air conditioning a very high summer priority, I'd be singing a different tune!

Lots of friends use portable, suitcase style folding solar panels with success. The portability allows for positioning the panels for best results at each campsite. I seriously considered this style but we don't have a convenient safe place to haul it or store it when not in use, and I have concerns about the temptation factor. Someone could decide they need it more than I do.

For my RV style, (and style is a significant factor in our design decisions) I much prefer a solar system that is permanently installed on the trailer so there's no chance of leaving an essential component in the garage or at a campsite. Nice idea, but our trailer barely fits in the garage now, with only 3/4" of clearance at the top of the door after I taught the trailer to kneel. Self imposed height restrictions, other equipment installations, and preferred trailer orientation when camping all had implications for available roof real estate. I actually thought I had only one possible location until I talked with the folks at AM Solar while we were in the Northwest last summer. One of their staff suggested the location I'm using.

Solar panels come in a variety of capacities, sizes, and efficiencies. My rooftop real estate limited us to a panel nominally 21 inches wide which cut down our options. I seriously considered the GS135 that AM Solar sells, but selected the 100 watt panel from Renogy because of its higher max power voltage (Vmp) and significantly lower price. The 100 watt panel will be marginal in the winter, but should cover us as long as we tilt the panel.

The next step was to head to one of the few places that I actually enjoy shopping. I can spend hours in the hardware aisle at our local Ace Hardware adapting my mental mount design to the available hardware.

Next up - building a custom mount.