I am thinking about how to install one or two 100W panels to my Scamp 16. I have a portable 60W set now but after installing a TV it's clear I need more power. I am debating between flexible panels and stiff panels. Given that the panels should not last as long as the trailer I worry a little about replacing flexible panels attached with VHB tape but it does appear possible in principle without damaging the fiberglass, although it may take a lot of effort with a razor blade.
Thanks.
I've seen this done. Dave with Lil Snoozy may chime in here has them glued to the front, but not sure if he uses an adhesive or vhb. The jury is still out on flexible panels, especially flat mounted in heat areas of the country. Ideally, solar panels need ventilation underneath to perform at peak and these installations won't have that. There are also reports of the film coating on flex panels cracking in short period especially in heat areas.
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Its a big subject with lots of pros and cons involved (more cons by the way) but regarding the question of VHB tape removal, see:
http://solutions.3m.com/3MContentRetrievalAPI/BlobServlet?lmd=1257835586...
(And note that some people have used a high test fishing line to cut the tape with good success)
I also have to wonder if you have done everything you can or should for energy conservation. Everyone is different but I get by just fine with a single 50 watt panel in summer, so one or two 100 watt portable panels should be enough for me pretty much anytime. I was going to mount a 100 watt panel on the roof but as life went on, I found that I don't need it. I am now leaning toward a 10-20 watt panel just to offset the phantom loads (esp. propane detector) for times when I do not have the battery master switch off. That way I also would not have to reset the time on my clock radio all the time too.
All the lights are LEDs, I think the main power goes to fans. We run the Fantastic ceiiling fan on warm days, my wife likes to sleep with a fan (~ 10W I think) and I use a CPAP (without humidifier). If there was reasonable sun that was OK for my 60W panels but adding a TV (~ 20W) which my wife likes to watch it was not enough for our last trip to Tahoe where our site had 3-4 hours of good sun/day, and one cloudy day. I'm sure that 200W panels is overkill for full sun but considering shade, clouds and panels fixed on the trailer it's better to plan for too much than too little. So I am really just trying to decide between holes in the FG for mounting stiff panels vs. VHB tape mounting flexible panels.
Doug O
Doug,
Have you upgraded your battery to a pair of 6 Volt Batteries?
I ask because a pair of 100 watt panels will provide way more power than you can store in a single 12 volt battery.
I would also suggest you consider a single 150/160 watt panel vs two 100 watt panels, fewer holes and easier installation.
If you haven't upgraded to a pair of 6 volt batteries, I would suggest you start with that. You may find that your 60 watt panel is adequate and that your real problem was simply not enough storage capacity.
As Always,
Happy Scamping !!!
Hi ManWithaVan,
The original battery with the trailer (only 1.5 yr old, group 27) went defective last week and I have just received a new 100Ah battery. This would be enough to last a few days with our usage pattern. I think that the existing 60W panels would also cover our usage, in full sun. The nice thing is that with the lowering price of panels it is no longer important to optimize on the cost of panels. a 200W system should be able to recharge a 50Ah deep discharge in only 3 hours of good sun so that makes winter, cloudy, shady camping much more available using only solar power. The 60W portable system I have, built up over a few years cost about $300 and now that buys a new Renogy 200W system.
I am debating between 2 panels vs. 1, but the idea of having one panel acting like an awning over the rear window where I occasionally put our window mount A/C has some appeal to me.
Thanks for the suggestions.
Doug
Doug O
A (very) rough rule of thumb that is oft’ quoted is one AH of battery capacity for every watt of solar generating capacity (i.e. a 100 AH battery for a single 100 watt solar panel). So it is probably a good idea to upgrade to two golf cart batteries if you go to 200-260 watts in panels. That would help get through the cloudy days also. While I do get by on one 100 watt panel and one 90-100 AH battery, you do use more power than I do.
But on to your question. I have done a good bit of reading and thinking about this very question for some time. I will tell you want I would do.
I have a standard Renogy glass 100 watt panel that weighs 16 lbs, and a 50 watt flexible panel that is very lightweight. Both were purchased for the possible installation on the roof of the Scamp (although I happily use either only as portables). The glass panel is the more square one compared to Renogy’s other 100 watt glass panel which is longer and narrower. I choose the squarer one because it would fit in front of the A/C on the roof better. If you have a roof A/C then the real estate for mounting solar panel(s) is a very limited. Remember that you do not want any shadows on the panels (even a very small shadow will really lower the output). I’ve seen too many panels mounted too close to vents and A/C units on RV’s roofs.
As much as I would prefer to not make any more holes in my roof, I have decided that I would not use VHB tape for the glass panel. One must follow the manufactures directions to the letter when using VHB tape in this high stress area, including removing wax, using sufficient quantity and taking into account the mounting surfaces, the wind load, etc. I would prefer to consult the 3M engineers in fact. And even if you do it all properly, I have seen at least one case where it appears that the tape held onto the gel-coat just fine, but somewhere on the highway, the gel-coat actually separated from the fiberglass and the solar panel become a projectile (with the accompanying potential liability if someone got hurt).
So, for the glass panel I would use four or six bolts through the roof with large backing plates on the interior ceiling and raised mounting brackets on the roof for air circulation. The roof already flexes if I push on it and the stress of a large sail (aka solar panel) pulling on the roof all the time at highway speed could cause long-term damage to the fiberglass so I would want to spread the load over much of the roof using backing plates with enough surface area. While there is the possibility of roof leaks, it is very slight if installed properly. Besides, I have been chasing leaks since I bought my camper almost a year ago – so much so that I could write a book. And none of the leaks were caused by any mod I did.
I would however consider mounting the 50 watt flex panel on the roof with VHB tape alone. It is light enough that even if it flies off at 65 MPH it is not likely to do much damage (unless someone was to serve off the road to avoid it and end up going off a cliff).
I think I would use spacers with the flex panel designed to provide sufficient contact surface while maintaining air circulation under the panel. Marine board is probably a good choice but I would double check that with the 3M people and also ask them how much contact area was required. VHB is like command strip mounting hooks in that it tends to release when stretched along it’s length so it is important to have sufficient contact area to overcome that sheer force. I don't know for sure, but for that reason it might be good to apply the tape perpendicular to the wind where you could. 3M could tell you that.
You could VHB tape the flex panel flat to roof (if it is flat enough) and the wind load would be much less, but expect the panel to fail after a some number of years (due to excessive heat) and to work at no more than 90% efficiency at first while slowly declining over months and years.
The ideal might be to actually construct a raised mounting surface (with air circulation) built into the fiberglass. In other words, remove the gel-coat and sand to bare fiberglass, then glass in some marine board or other structural element that you could put screws into.
Thanks Gordon, good thoughts. I would only consider VHB tape for flexible panels so the surface area bonded would be quite large. The heat dissipation issue is a concern, I think I'll poke around a bit and see if I can find any real data on the associated performance issues. The flexible panels are quite thin (1 mm or so) so I would think that cooling from one surface should not be that much worse than cooling from two surfaces.
Doug O
Doug,
I'd definitely upgrade the battery long before I'd add more panels. What battery do you currently have? Group#, amp hour rating, etc. Doesn't matter what panels you have if the battery capacity is not sufficient for your usage. I also think you still need to look at your usage. I.E. Is your tv a 12v or are you running it through an inverter? Inverters are very inefficient and will pull quite a bit more juice running a tv then a direct 12v tv. Same with the CPAP you mention if it is a 110 appliance and running through an inverter. They do have 12v models for travel available now from what I've heard. The MaxxFan is no issue running overnight etc. if your battery bank is robust.
If your battery is 100 ah you can use 50 ah before you have to add back in. If your current situation you are starting out with a full battery and running out by morning, all adding panels will do is fill the battery back up by 10 am vs 11am with your current panel, but you will still run out of juice by morning. Another consideration is that a 60w panel that you can position correctly and move during the day will outperform 100 w fixed roof panel. You can also put a 25ft extension cord and locate it in sun when you are camped in shade.
I know on my trailer that my daily usage is 7-10 ah (fairly easy to find this out with some basic gauges while dry camping) depending on whether I'm running the heater or not. The twin 6v have a 232 ah rating so I can safely use 115 ah before I need to charge. At my usage rate I can go on battery alone for 8-10+ days. Once you have that information you can then determine where the weakness is in your system and upgrade that. Me personally, I wouldn't buy panels and drill holes in my trailer until I knew all the above and fixed those items first.
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Hi Greg,
I have been using my portable solar system for several years, building it up from 5W, to 30W then 60W with addition of a second 30W panel. I know that for just me and my CPAP the 30W system in good sun works out OK.
We are not using any inverters, everything runs directly on 12V, the lights are all LED and the TV is about the lowest power one I could find. For our usage a 100Ah battery is good enough to last several days. The thing that is great now is that for what I spent developing the 60W portable system (~ $300) you can get about 200W system and only need about 3 hours of sun every couple days to keep things topped up, so winter, cloudy and shady camping are not much of an issue. Well, 200W with flexible panels is more like $400.
Anyway, I am not really asking someone to optimize the system for me, at this point I just want feedback, based on experience, about VHB tape mounting vs. mounting with holes in the fiberglass. I am sure that if the goal is to get through 7-10days camping without shore power the simplest thing is just to stock up on batteries, but that is not really my question.
The comments & feedback we can get on this forum and the FGRV forum are just fantastic and I love it, and appreciate it. How did we ever live without the internet? Thanks.
Doug O
Doug,
Thanks for the additional information, now I've got a better understanding of what you have and where you are going. Quite a few folks have successfully used the VHB tape over the years to mount both solar panels and even awnings. AMSolar, one of the top RV solar outfits uses VHB tape in their installations and claim to have never had any issues since 2002. From what I've read over the years, it seems to be like anything. Apply it wrong and it will most likely fail, apply it properly and it will most likely last a lifetime.
Personally, I would also put some bolt through in addition to the tape just for my peace of mind, but I think a combination would be the best of both worlds and not cause one to drill too many holes to mount solar on their trailer. As I indicated earlier, the flexible panels are in my opinion, not quite ready for prime time and while I love the idea I'd personally put fixed panels on over flexible.
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