Flexible Solar Panel Install – an additional 100 watts!

After testing the solar power in Moab, Utah, and in my driveway, I came to the conclusion that while the hot sun of Utah kept the battery topped off I noticed that in my shadowed driveway that the battery would slowly drain. If I hope to boondock for longer periods than a couple days I think a second 100 watt flexible solar panel attached to the roof would serve me well in keeping the battery topped off.


The rigid solar panel will have a flexible solar panel buddy on the roof of my 13′ Casita!


Flexible Solar Panel

I had previously used the Renogy 100 Watt Solar Kit with Adventurer Charge Controller. The panel that came with the kit is the regular rigid kind that is within a metal frame. I decided that a flexible solar panel would suit the roof of my Casita better than the regular rigid version as the flexible solar panels are lighter. I decided on the HQST 100 Watt Flexible Solar Panel:

It’s a quarter of the weight at 4 lbs vs 16.5 lbs.

3M VHB Tape

I’ve also decided to not use screws to attach the panel, but to use 3M VHB tape:

VHB stands for “Very High Bond,” and they have several videos of manufacturers using the tape in place of rivets and other mechanical attachments, saving both time and money:

3M video on VHB tape. Will use this to attach the 100 watt flexible solar panel.

3M video on VHB tape. Will use this to attach the 100 watt flexible solar panel.

That two of the testimonials are from RV manufacturers (Yetti and Showhauler ) which bodes well for a rooftop install!

My concerns with a mechanical attachment, such as screws, are additional holes in the roof. I’d like to avoid that, if possible.

I consulted a 3M representative who recommended 3M VHB version # 4945 (or #5952) after I described the surface materials (gel-coated fiberglass, and the flexible solar panel plastic). He did mention that the tape would only be as strong as the gel coat and paint, rather than the fiberglass, and recommended considering abrading the surface down to the fiberglass, cleaning the surface with a combination of isopropyl alcohol and water, and then using an adhesive primer on the back of the panel prior to applying the tape:

So, attaching with the 3M VHB tape and using a lap caulk around the edge seems reasonable:

I decided instead to use Eternabond instead of VHB and Lap Caulk. Tape is just less messy than using lap caulk, and Eternabond seems to be sufficiently strong and waterproof for my application: Eternabond

What about the wires?

The only hole drilled will be for the wires to go into the trailer, protected by a cable entry gland:

Flexible solar panel wiring will enter through the roof with this cover.

Gland for the flexible solar panel wiring.

I’ll use the tape as well as the caulk for that as well.  The panel wires will go through the “glands” sideways. It acts as a waterproof cover, and will be nicer than a caulk covered hole in the roof!

No looking back(?)

Here’s the thing: I can always add a mechanical attachment. The holes will still be available to add a screw, so the adhesive will just be an additional attachment method.

I’ve seen other people saying they used this method, with no remarks that it failed. I have heard of industrial hook and loop (velcro) attachments failing, with solar panels flying off onto the freeway!

The tape can (with effort) also be removed.  You’ll need a 3M SMART Removal tool, as well as a 3M Stripe off wheel…but hopefully I won’t need to do that!

Only time will tell if this method will work well. But, I figure that If this does work, then I won’t have additional holes for rain to seep through, and can offer this as an alternative to drilling more holes in your RV.

Rain seems to be the universal destructor of RVs, and I’d like to do what I can to eliminate water entry points.

Check out the YouTube video: https://youtu.be/ZKQqHoT0fDw

Products used:
HQST Flexible Solar Panel
Eternabond tape
Link Solar Cable Entry Gland
RENOGY 5 Pair MC4 Male/ Female Solar Panel Cable Connectors Double Seal Rings for Better Waterproof Effect
1″ hole saw

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