Best method for attaching flexible solar to roof

[SameGuy]

I am in the planning stages of adding a couple flexible solar panels to the roof of my FWC Hawk. Wondering what the collective brain trust here recommends. Just watched a you tube video where someone used Eternabond tape, which seemed to work well but a little water wound up getting under the panel on the corners. I'd like to use flexible panels to save weight, 10lb for 2 panels vs 30+lb for ridged. There is no rack up there now, however that will likely change by the end of the summer.

 

[Superduty]

Can you share a link to the panels you plan to use?

Sent from my SM-G973U using Tapatalk

 

[SameGuy]

I think I'll be going with these based on some ratings I have read for durability and efficency. https://www.amazon.com/BougeRV-SunP...d=1561037495&s=lawn-garden&sr=1-2-spons&psc=1

 

[john61ct]

They are more expensive, and don't last long compared to rigid framed panels, even mounted perfectly maybe 3 year average, compared to decades.

They need to be securely mounted so no flexing once installed.

Ideally with an air gap below, to prevent their getting very hot, hurts output and longevity, can really fry the finish below too.

A rigid aluminum plate is best, some make do with polycarbonate.

 

[dwh]

If you glue them down, the put a rack over them, the partial shading from the rack will kill the solar panel's output and you will have wasted your time.

Glue them to a thin sheet of aluminum and bolt that on top of the rack.

 

[SameGuy]

My main concern regarding flexible vs rigid is weight. At some point I will have racks installed to haul my kayaks, I'm assuming the racks will be in the neighborhood of 30-40lb, so another 30 plus pounds for rigid panels vs. 10 for flex. I'm not sure what the limit is for being able to get the top up on the camper, but I would guess 70lb. would make it somewhat harder to get up. I understand that any shading on a panel will make it useless and that flexible panels are not as durable as rigid. So maybe I'll ask the question differently. Those who have mounted flexible solar panels to their roof, how did you attach them, what would you recommend?

 

[peekay]

try Eternalbond. I think that's what the RV guys use.

 

[Wyuna]

glazing adhesive is flexible, it was recommended by the solar panel manufacture for fixing to the roof.

I ended up making a light weight aluminium frame with supports to raise the semi flexible panel off the roof for airflow and fixed it with double sided tape and a few rivets.

glued the aluminium frame down with Sikaflex, still good after 18 months, this panel is is a commercial semi flex panel with 25 yer warranty, so im expecting to get at least 5 years out of it on a van

 

[john61ct]

3M VHB tape

 

[luthj]

VHB works well. I have seen folks use VHB backed Velcro products with some success. Note that mounting the panels under the rack will make there output very low due to partial shading.

 

[john61ct]

I've seen slide-outs, like rigid awnings that pull out from under the rack, triple the available square footage.

But yes, panels usually need to be the highest thing on the roof.

Any shading at all is a killer, even just a leaf or dust can kill most of a cheaper panel's output.

Tilting can double it!

Ideal efficiency comes from one panel per controller,

e.g Victron 75/15 SmartSolar MPPTs, each matched with a high-voltage 250+W panel

Also getting panels made from high-efficiency - maximum Watts per square inch - cells like SunPower.

But SP sells panel makers graded cells, quality A through D, at huge price differences.

Key takeaway - do not shop for panels based on price alone if you care about such distinctions.

 

[workerdrone]

Ditto on the warnings about shading - I shake my head at so many solar installs that I see - it takes so little partial shade to decimate your output. And some are installed so they will NEVER get full sun.

I have a flexible 160w Renogy which has been on 3 vehicles so far and I love it - I just use a bead of adhesive around the edge so it can be easily removed for the next rig - easily stolen I guess too lol. But it stays on at speed.

Was concerned about inefficiency or damage due to heat, since sometimes it seems I could cook eggs on it and there is no cooling airflow underneath like with a rigid panel. But my controller indicates up to 149w so that's pretty good.

Complete overkill for one fridge but I've found overkill is nice on cloudy or less than ideal days - I'm getting a couple of watts even right after sunrise (worst angles) and maybe 20 on cloudy days.

 

[SameGuy]

Ditto on the warnings about shading - I shake my head at so many solar installs that I see - it takes so little partial shade to decimate your output. And some are installed so they will NEVER get full sun.

I have a flexible 160w Renogy which has been on 3 vehicles so far and I love it - I just use a bead of adhesive around the edge so it can be easily removed for the next rig - easily stolen I guess too lol. But it stays on at speed.

Was concerned about inefficiency or damage due to heat, since sometimes it seems I could cook eggs on it and there is no cooling airflow underneath like with a rigid panel. But my controller indicates up to 149w so that's pretty good.

Complete overkill for one fridge but I've found overkill is nice on cloudy or less than ideal days - I'm getting a couple of watts even right after sunrise (worst angles) and maybe 20 on cloudy days.

Workerdrone, what kind of adhesive do you use? Do you have any pictures of your install? I have seen people use Eternabond to simply tape them down to the roof, but that stuff looks like a pain to remove.

 

[workerdrone]

It's the opposite of nice fab work lol - I probably spent less than an hour installing panel, battery, controller, fridge, wiring - and it can be removed even faster. I just used some exterior silicone adhesive/sealant, can't remember the brand sorry.

Cracked the front slider open a bit on the topper and just fed the wires through there to the controller. Liberal use of plastic zip ties. Fatter wire than will fit into the controller receptacles, but I just trim down the last 1/4 inch and use the bigger stuff to minimize V drop.

 

[SameGuy]

Awesome, thank you.