Flexible Solar Panels.

[boobook]

I currently have 115W of solar on the roof and an 80W panel on my front box which is removable, but a bit heavy. This normally works well but I want to get rid of it and reclaim the space on top of my box for other things.

I have been thinking about the semi flexible solar panels which like all solar are coming down in price.

After much measuring and checking I am about to buy 2 80w solar panels as per below. They are 919 x 690 x 2.5mm, and have a 20mm thick junction box. I plan to somehow mount them so I can easily remove then to use them as portable units when I'm parked in the shade.

http://www.ebay.com.au/itm/160W280W-SemiFlexible-Solar-Panel-for-RV-motorhome-poly-/221091416073

They fit nicely side by side on the rear hatch, mounted to the protruding parts on the moulding in a double portrait format.  When the hatch is up, it will work well if the Tvan is facing north, and ok to average otherwise, that's when I may remove them and use them as portable units. They only weigh 3.5kg each instead of 9kg each for my old ones, so they will be easy to carry around and shouldn't affect the strut / opening operation. I'm thinking of mounting it with some posts through the mounting holes, and velcro. Actually I think they will be ok in place unless it is hot AND I'm facing south AND I am in the shade. My total of 275w on the roof should generate 30 - 40 AH even then. All I need is full sun for 1 1/2 to 2 hours (20A)

The purpose of this post is to ask if anyone sees issues in mounting them to the rear hatch wrt driving wind, mechanics, etc. I checked and they will easily clear the rear deck when it folds up.

I don't think I'll get a job with Who Weekly in their photoshop department, but hopefully below will give you an idea of what I'm talking about.

[turtles]

Hi Tony, My only hesitation in mounting your panels on the rear hatch is the amount of dust we accumulated there on our last trip. To be effective you would need to clean them. 275W is an awful lot of power, what are you running off them. Admittedly we were up in the Northern Territory with lots and lots of sunlight but we found the factory supplied panel on the roof (provided it was clean) kept the battery charged enough to run everything. Our 80ltr engel fridge lives in the back of our 4wd and runs off an auxiliary battery kept up to charge by 120w free standing panels we carry in the 4wd. Our setup works well for us but I am interested to know what you are running in the Tvan.

[boobook]

Yes I am aware of the dust, but it covers the roof panels and my current front mounted panel anyway and  it should be easy enough to wipe then before I put the hatch up. Any dust will reduce efficiency by 20- 40% even on the existing panels.

I agree that 115w is more than enough in clear country up north, however I spend a lot of time in the high country with lots of tree shading, clouds and mountains in the way. It can be difficult to harvest the sun and I often move my portable panel around chasing it. I am lucky to get a couple of hours of good sun without a lot of work. 2 x 80 watt panels that are very light change the game and 275W of panels would be lucky to generate an average of about 80 watts or so under these conditions. Barely enough to keep up with a fridge on a hot day.

I have an electronics background and have done the sums, Solar watts are like air. If you don't have enough you die. If you have too much it doesn't matter. And if I can lose a few kg on my camper along the way all the better.

I am mostly concerned about any issues with the mounting and mechanical aspects of the installation.

[boobook]

I have purchased them on Ebay after much double measuring and checking.

I am now thinking of mounting methods. Velcro, magnetic stips or some quick release pin system through holes in the panels.

I'm currently thinking of velcro and will run with that to start unless anyone has a better idea.

[chris_a]

I have also looked at the rear hatch as a potential location for solar panels, although it has not really been viable until the introduction of the slimline panels.  How are you planning on connecting the panels up to charge the batteries - a permanent connection or something you will rig up every time you stop?

I am also interested in understanding what you are running. We run a 40ltr Engel as a freezer and our 50 watt solar panel can't keep up with the demand on power. Trying to work out what is going to give us a greater degree of self sufficiency in terms of solar panel capacity.

[boobook]

Chris, I too have eyed the spot for a while, but normal panels are too heavy and thick. Until recently the flexible ones were too expensive, especially since I have 115W fixed ( and a 80W removable on the front box which will go), anyway. But while that is more than enough in good conditions and away from shade, it isn't near enough in a valley in the high country.

For your use, you really need a minimum of about 160W to keep a fridge and a few lights going indefinitely in good conditions, and freezer is triple that at least. Freezing uses 3 - 3.5 times the power of a fridge. I suspect that if you have 100AH of battery then 50W won't even add a couple of hours of capacity. You would only get about 16 - 18 hours before going below 11.9V and damaging your battery. You should consoder cryovacing as an alternative.

As to my power use. I have a National Luna fridge which is pretty efficient, LED's etc and a Stereo which can suck a few amps when we are camped alone. Also I have rigged up a gas Hot Water System and pump that draws water up from a river. I often go with a few families with tons of kids and the shower can be running for an hour a day! Though it doesn't get any use when it's just the boys and I for some reason, LOL. However the main issue, even with only the fridge is that solar efficiency drops significantly with any shading and it is hard to find a treeless, cloudless camp spot in the high country. So I tend to chase the sun with the portable panel at the moment.

For $420 for 160W I thought it's time to dump the 80W that takes up space and weight on the front box. Currently I plan to use velcro to attach the panels to the hatch. I use red Anderson connectors for the panel side of my regulator which is 20A. I will add 2 to the hatch for the panels if they aren't too ugly. I have previously wired lights into the hatch so will do something similar for the new panels. They will be normally wired in so they just work as soon as I lift the hatch. If I want them top be portable, I just disconnect one or both and move them. I already have 2 x 15m thick extension cables to then place the panels away from the camper, either together or in separate spots. The only issue I can see at the moment is that I will probably have to make the call about removing them at set up time. It will probably be too hard to get to them after the rear tent is up.

I have done some calculations as to the efficiency given the angle of the hatch to the sun. If I face the van North, it is almost perfect, better than mounting it flat. Worst case is if I face the van south. In winter the new panels will generate nothing when on the Tvan. That's ok because the fridge isn't working as hard, and panels are cooler, and I always seem to get 100% charge over several days. If I run low then I move the panels and Bob's you uncle.

In October and March,  I will get about 100w max from the new panels in theory on a clear day ( total about 200W). In December to Feb it rises to about 140W, total about 250W, when the sun is out and not blocked. Trouble is that the sun is usually blocked in the high country and 2 - 3 hours of 200W is ok. 2 - 3 hours of 50W - 100W is only 10 - 20 AH, not enough to keep up with a good fridge.

Soooo all that means I got the extra 160W because a)it is the maximum that will fit, and b)with all those inefficiencies, it should keep up with the power use, even if I leave them on the hatch most of the time. If I go on longer desert type trips, I may remove one or both as they generally won't be needed and I will tend to keep moving more. In the high country I think they will stay on the hatch 90% of the time but I have the option to move them on those occasions that require a boost.

I also  put series blocking diodes on all my panels to stop shaded panels using power, that drops the peak power output too.

[boobook]

Oops double post

[boobook]

Bad morning.

[gregbroome]

Hi Tony,
Is there really anything to be gained by mounting panels on the TVan? I can't help thinking you potentially get much more input from solar if you can leave them portable and shift as needed.
That can be inconvenient, but also solves mounting issues. Storage shouldn't be bad, plus they are kept cleaner. In my experience, living in the tropics, the roof mounted panel is almost useless as I always try to park under shade. I then use a cheap Chinese folding 120w on a lead with an Anderson connector to the drawbar. Have an adaptor for this so I can plug into Merrit plugs if lead won't reach, but that probably causes volt drop.
I am interested to hear how you connect these panels to your batteries. Plus I carry a small gennie, as hot, humid and cloudy weather is diabolical with solar. Have high power requirements for laptop and photo editing, hard drives etc on top of fridge use.
Cheers,
Greg.

[boobook]

Hi Greg, there in no doubt that I will get more out of the panels when they are in portable mode and I move them to chase the sun, but by my calculations and experience from the existing system, it will be more than enough much of the time in place. Where I frequently go, unless there is a big open spot, everywhere gets both shade at times and sun at times. If it's out of summer I tend to camp away from under trees which tend to be heavy when the branches drop, if it's summer and I am parked in shade, then I will move them, but I want to get away from keeping a constant eye on them, moving 80W or so to follow clear sun. I am working on 275W of panels in full sun 30% of the time is as effective than 80W 100% of the time.

I have to store the panels somewhere, and on the rear hatch hidden by the deck is not a bad spot, with the added bonus that I don't have to unpack them 80% of the time. 

[boobook]

I got my new panels today and did some testing. The panels are great. They are about 2mm thick at most apart from the junction box which is about 20mm.

I'm still wiring and mounting the panels but ran them in parallel with the roof ones. Melbourneites will know that today was mostly about 75% cloud cover with full sun for bursts of about 5 minutes at a time, for most of the day.

I put 38AH into the batteries over about 5 hours. That's an average of about 7.2 amps. Not too shabby for a day like today.

I am pretty pleased with that.

[Patrol Dude]

Hi BooBook, once you have installed them, post some pics please mate. Very interested in this. Cheers

[boobook]

No problem. I will be away cup weekend in the Buckland Valley and will get to test them in partial shade too.

[gregbroome]

I think there will be a lot of folks taking a good long peek at this particular installation!
Sounds fantastic if they can be removed without much hassle.

[boobook]

Ok it's all installed and working. I'm heading out for a weekend in the Buckland Valley so the new panels got to see sunshine for the first time while mounted.

I swear these panels were made for the rear hatch in the Tvan! The dimensions are just right to sit side by side and attach to the raised parts of the hatch. There is a raised terminal block on them, which just clears the frame of the rear deck if mounted at the right height.

They are attached with velcro and are quite sturdy when on. I have no concerns about them moving. Also they easily peel off and I can move them if parked in the shade. I have about 20m of heavy duty extension cable. I have standardised on red Anderson connectors which won't mate with the grey ones for all connections on the solar side of regulators and put serial Schottkey diodes in series with each panel so they don't interfere with each other when shaded. They weigh almost nothing. I can lift them with 2 fingers. ( both hands for my old 80W panels) So I have replaced about 12kg on the front box for 80W with less than 5kg for 160w on the rear. Gotta be happy with that. Also my batteries were nearly full, so it may have given more with low batteries.

I tested them last night. I have 25+25+65+ 2 new 80W panels. While that seems a lot it is designed for the conditions described above. Yesterday at about 4PM with an overcast sky, and the camper pointing west, I was pulling 4.5A. Not bad...especially sice one 80W and one 25W were heavily shaded by a tree. So hopefully I will meet my goal of not having to remove them 90% of the time.

More details when I return from the weekend camping. I am powering 2 fridges this weekend and an inverter so it should be a bit of an acid test. I also have to tidy it up a little, especially paint the red Andersons on the rear hatch white.

Can't wait to see a 20A charge rate in full sun.