Rooftop Solar – Magnetic Mount

A year ago I bought a couple of portable solar panels, thinking that they would be useful for charging the batteries in cases where we camp more than a couple days in one spot. At the time, running the engine didn’t charge the batteries very quickly and running the generator was (and is) far too noisy. A year has gone by, and we’re questioning whether or not they’re useful enough to carry along, considering the space they take up in the campervan.

  • Portable solar really only helps when when we stay in one spot & the sun is out for most of the day. They are less useful in campgrounds with lots of shade, in cloudy weather, in winter when the sun is low, or when we drive the camper long enough to recharge via the alternator.
  • We don’t stay in one spot very long. I’m interested in seeing stuff, not spending time in one spot catching up on my reading list and contemplating the meaning life (hint – it’s not ’42’). I can read and think at home. So unless there are lots of scenery and trail options within walking distance of where we are camped, we’re going to drive the van every day anyway.
  • I upgraded the wiring from the Transit starter battery to the DC-DC chargers so we can now charge at at a fairly fast 60 amps whenever the engine is running. If we run the engine an hour – I.E. driving to a trailhead and back, the batteries are charged enough to last another day. The Transit alternator probably can charge at more than 60 amps, so with time and money I can enhance that charging option.
  • The panels are roughly 2′ x 4′, which makes them hard to store. We are currently standing them upright behind the couch during the day and while traveling and transferring them to the front of the van at night and back in the morning.

Given the above, we decided to re-think things a bit. The new plan is to rely more on charging via the alternator, on storing more power in larger battery banks, and rely less on portable solar power.

We’re going to mount one of the portable panels on the roof and store the other panel under the couch and still be able to use it where we need portable power. My thinking is that a rooftop panel that can contribute power anytime the camper catches some sun is more useful than a portable panel that needs to be manually connected and monitored. To be able to store the one portable panel under the couch, I’ll have to re-design the rear storage area.

Mounting with Magnets?

The factory panels are stuck down with some sort of adhesive. I’m not enthused about gluing the new panel down – mainly because it’s pretty close to being permanent and the adhesive will be really hard to clean off the roof if something changes.

Unlike other campers and RV’s, van roofs are steel. So why not take advantage of that? How about glue-less semi-permanent mounting using rubber-coated neodymium magnets fastened through the grommet holes in the panels?

Anti-Scratch Neodymium Magnet with Rubber Coated and M6 Male Thread, Super Strong”

“Anti-Scratch Neodymium Magnet with Rubber Coated and M6 Male Thread, Super Strong” magnets are available on Amazon in various sizes and strengths. I’m going to start with the 26lb versions, one in each corner. I figure 26lbs * 4 will be enough to keep the panel from moving around or flying off. If not, I can add a couple more magnets or buy stronger ones. I suspect that there will be a tendency to lift the panel, and perhaps the panel will want to flutter in the breeze. I’m not sure that I’ll be able to detect that if it happens. If the panel slides backwards, I’ll be able to detect it fairly easily.

These are cheap imports, so their ability to withstand the weather without falling apart or corroding is unknown. I’ll have to keep an eye on that. They only have to last until I change my mind and re-design everything – which historically has not been very long. đŸ˜€

I stuck strips of foam weatherstripping on the back to help maintain space between the panel and the roof. This should keep the roof from getting scuffed up and (perhaps) allow the panels to run a bit cooler.

The panel will be shaded by the AC any time the sun is toward the front of the van. The two factory panels are up front, so the front and rear panels will never be shaded at the same time.

Solar Panel, Magnetic Mount

To run the wires down to the controller, I ended up having to put a hole in the roof and tear a bunch of the rear interior apart. I now have an ‘opportunity’ to redesign the storage area in back so it’s larger and easier to access, to replace the poorly functioning bug screen with a homemade one, and to figure out a way to store the other portable panel in a spot where it doesn’t have to get moved around every night.

I have two Victron MPPT controllers & will use one for the two front panels and the other for the rear panel, so charging will be optimized at all times. The remaining portable panel is identical to the rear panel, so I’ll set that up so it can be plugged in and run in parallel to that panel. I considered using a single MPPT controller for both the two factory GoPower 100W panels and the new SunPower 110W panel, but the voltages (Vmp) are just a bit different, so I’m not certain how well that would work. It seems as though there are corner cases where a lower voltage panels would act as a current sink for a high voltage panel.

If someday we decide that we want to drive a thousand miles just so that we can sit in one spot for days at a time, the portable panels might be more useful. If that happens, though, we’ll have a problem with fresh, black and grey tank capacity and will have to drive someplace every few days to empty and fill the tanks. The drive will recharge the batteries.

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