Single or Multiple Panels?

[klpauba]

I was kinda hoping that I could install flexible panels on my TM but it seems most suppliers are depleting their stock and then discontinuing them. I'm now looking around at the rigid panel offerings.

There are some higher power (and voltage) panels available but there would be enough space on the back shell of my 2720SL for just one. The alternative is to get two or three smaller panels. The larger panel would have the advantage of simpler wiring (no combiner plugs/box) and have fewer lbs/watt (due to much less aluminum). The downside of the larger panel are that the buyer usually pays the shipping (which is much higher due to their size/weight). I've been comparing poly panels from Missouri Wind and Solar -- the 250 W one and some of the 100 W offerings. I've already purchased an MPPT controller so I'm not too worried about the higher voltages of the 250 W panel.

What other advantages/disadvantages should I consider when comparing the two panel sizes?

[scrubjaysnest]

During the installation process the larger panel may be for difficult to handle. When we had the 120 watt panel it was easier for two of us to place it on the roof. Higher Vmp may allow smaller wire for a little cost savings. If you have a tilt system like we do there is less to mess with in tilt brackets.

Shading on the panel will have more affect in some cases. With two only one may be in the shade.

[Lesherp]

This is the panel I bought. They have free shipping. With the rocker foot mount I am able to take the panel off the roof and put it in the sun if need be. I have only had to remove it once in 3 years even though I have camped in many very shaded sites. It would be challenging to remove and replace it on the roof by yourself but it was very manageable for DW and myself. For us we have had fully charged batteries by sundown 99% of the time.

http://www.amsolar.com/home/amr_1363129012196/page_360_43/s-sf160_solar_panel_with_accessories.html

[rickst29]

If you went with all aluminum+glass framed panels, your best choice (Watts per Dollar) would be "Windy Nation" 100W Poly Panels. But the weight of each panel is 17.6lbs - 3 of them, on one shell, adds over 50 lbs. Even with lift bar torque adjustments set to maximum (screws all the way in), that would be quite difficult to lift. My 2619 is a struggle with 2 "Renogy" panels and one flex, at about 37 lbs. I would not be able to lift the front shell on my 2619 with 3 aluminum+glass framed panels. (The torque adjustment screws are already all the way in.)

Instead:

"Windy Nation" 100W panels, at standard "max" conditions, put out 5.6A @ 18V. To reduce weight, we want to replace either one or two of them with lighter "flex" panels. And, with an MPPT Controller and panels mounted in series we want the flex panel to match the current - not the voltage. This is the optimum panel, for Ebay Purposes: http://www.ebay.com/itm/181747215111. If you want a really easy lift, then buy two "Sgzestore" Flex and use the sole "WIndy" panel in the middle. (Always put the odd one in the middle, to avoid side-to-side misbalance.) If you want to save $100 or so, then buy two "Windy" panels and one "Sgestore" (Flex in the middle, like my arrangement.) It's a harder lift, but the $100 difference buys lots of cold beers. ;)

Right now, there aren't any flex panels which match the current output of the "Renogy" 100W mono panels (which put out only 5.3A each). That's why the "Windy Nation" Poly panels are a better choice for you, right now.

[scrubjaysnest]

Part of the reason for the redo I just did was to address some of the weight issues mentioned above. The two 80 watt panels, not recommended at this time because of cost/watt, are slightly lower in weight then either the Renorgy 100 watt panels or the Missouri Wind and Solar 100 watt panels. Because of problems in the past with the flex panels, your lightest weight option, I chose to stay away from them. The early flex panels were Amorphous cell material, sprayed on, and tended to flake with flexing. Series is a good way to go if panel shading isn't a problem. This lets you use smaller wire with a cost_weight/foot reduction.

[klpauba]

I really appreciate all of the replies. Thanks folks.

Scrubjaysnest, you answered my request very well. If it wasn't for the dead weight, I would really prefer 3x100W.

Lesherp, that's very interesting that your installation allows you to remove the panel in shady campsites. I really like that idea but I don't know how keen my DW would be with it. I also took a look at your album and I must say those are some beautiful photos you've taken!

Rickst29, I really, really appreciate your taking the time matching up the rigid and flex panels. I worry about the major suppliers (Renogy, Windy Nation among them) discontinuing the flex. It makes me think they've had a lot of warranty issues. I also see that the supplier you mentioned doesn't warrant the product except for DOAs. The price cuts a little deep, too, but I think my DW would prefer them -- when I mentioned that I'd like to add solar she mentioned as long as they can't be seen she would be OK with them (!). If I were to do flex, I would get 3x100W. I see these flex are available at $1.90/W using the same cell provider --http://www.ebay.com/itm/Semi-Flexible-Bendable-100w-100-Watt-Lightweight-Solar-Panel-12v-Battery-OffGrid-/161668810421. If you had to buy another flex today (given current prices and lack of warranty), would you do it?

[Padgett]

I went with two 100W monocrystaline panels on the rear section of my 2720SL (three would fit but two seemed a better match to the rest of my system (two GC2 batteries).

Not difficult to open.

[Craigrrr]

I went with two 100W monocrystaline panels on the rear section of my 2720SL (three would fit but two seemed a better match to the rest of my system (two GC2 batteries).

Not difficult to open.

Padgett, can you post a few pics of your wires running down and into the TM?

[scrubjaysnest]

Good pictures here:harveyrv install (http://www.trailmanorowners.com/forum/showpost.php?p=77228&postcount=1)

and here: lovetocamp install (http://www.trailmanorowners.com/forum/showpost.php?p=101477&postcount=37)

and here: My install before redo (http://www.trailmanorowners.com/forum/showpost.php?p=119989&postcount=9)

and I haven't found padgett's yet

[Craigrrr]

Good pictures here:harveyrv install (http://www.trailmanorowners.com/forum/showpost.php?p=77228&postcount=1)

and here: lovetocamp install (http://www.trailmanorowners.com/forum/showpost.php?p=101477&postcount=37)

and here: My install before redo (http://www.trailmanorowners.com/forum/showpost.php?p=119989&postcount=9)

and I haven't found padgett's yet

Thanks Scrubjaysnest appreciated it!

[rickst29]

I see these flex are available at $1.90/W using the same cell provider --http://www.ebay.com/itm/Semi-Flexible-Bendable-100w-100-Watt-Lightweight-Solar-Panel-12v-Battery-OffGrid-/161668810421. If you had to buy another flex today (given current prices and lack of warranty), would you do it?
I've not yet experienced hail, but the has been working great so far. Those SunPower mono cells are darn good. I absolutely would buy a flex again - in fact, if I was doing the whole configuration over again, I'd buy 2x flex with only a single aluminum+glass framed panel.

[klpauba]

So you would buy 2x flex and 1x glass ... not 3x flex? If not, why? Thx.

[Craigrrr]

I just gotta ask... I have heard the flat flex get too hot just layed out on an RV roof. Any insight on that?

[klpauba]

I have heard about the heat problem when mounting directly to the roof too.

My plan is to fashion something out of 80/20 t-slot (http://www.ebay.com/itm/8020-T-Slot-Aluminum-Extrusion-15-S-1575-x-72-N-/330558913430), corrugated polycarbonate sheet (see http://dainyrays.blogspot.com/2014/04/installing-semi-flexible-solar-panels.html) and Stayput fasteners (see the second set of pictures at http://www.lifeonthehook.com/2016/01/29/our-vision-realized/). My worry then becomes how long before someone steals them -- I need to figure out something to make them harder to remove.

[scrubjaysnest]

...............snip -- I need to figure out something to make them harder to remove.
My current method since I made them to tilt is allen head 10-24's. When I removed the 120 watt panel it left a bracket under each 80 watt that I could loop a lock through it and the panel. A little more difficult with flex I imagine.

[Padgett]

Just a quick and dirty. Used channels on the side then tiewrap on arm then wrap down under and into the hole where the battery used to be in the rear compartment.

[Craigrrr]

Just a quick and dirty. Used channels on the side then tiewrap on arm then wrap down under and into the hole where the battery used to be in the rear compartment.

thanks

[rickst29]

I just gotta ask... I have heard the flat flex get too hot just layed out on an RV roof. Any insight on that?
That can happen with insulating roofs - painted rubber, asphalt, etc. The TM is immune to those effects, because the roof is aluminum (a great conductor). And, I speak from actual experience in INTENSE sunlight (altitude 9000 ft). My aluminum-framed panel surfaces, with air underneath, get much hotter than the flex panel surface.

[rickst29]

My plan is to fashion something out of 80/20 t-slot (http://www.ebay.com/itm/8020-T-Slot-Aluminum-Extrusion-15-S-1575-x-72-N-/330558913430), corrugated polycarbonate sheet (see http://dainyrays.blogspot.com/2014/04/installing-semi-flexible-solar-panels.html) and Stayput fasteners (see the second set of pictures at http://www.lifeonthehook.com/2016/01/29/our-vision-realized/). My worry then becomes how long before someone steals them -- I need to figure out something to make them harder to remove.
Definitely DON'T do anything like that! Those "Stayput" clips require you to pierce the shell - which was easy for the boater with fabric, and possibly necessary because the fabric can wear out over time and flap around in strong winds - but a terrible thing to do to a TM shell, which is solid, stable, and waterproof (unless you "screw it up" on purpose).

In my configuration (kinda heavy, with just one flex panel in the middle), the length-wise "joint" of the half-shells makes a sudden rise. In glueing it down, I had to leave a 50% gap along the front "skinny" edge... and I left the back edge completely unglued, so that water which enters at the front gap has a place to exit. The longer "sides" are glued down completely.

That's another reason to prefer two flex and one "solid" - with double flex panels, you mount the solid-framed panel above the midline, and you don't have to worry about the bump at all. Then, on either side, the flex panels can glue down on all 4 sides, to smooth surfaces. I used strips of VHB tape, which has been strong and stable on my hard-framed panels for multiple years. You could also consider fast-cure 3M boat sealant (the "permanent" stuff), instead of VHB tape. But both are far too difficult for any thief to bother with removal, primarily because the front shell of your Trailer is secure in the raised position, unable to take down (because of the locked front door).

Note also, I specified a flex panel with the wiring junction box AND connectors on the upper side - so that your whole panels can be glue or taped completely flat. ;)

[rickst29]

So you would buy 2x flex and 1x glass ... not 3x flex? If not, why? Thx.
The 3rd flex wouldn't mount flat (becuase it goes over the midline "bump"). And, the first 17 lbs of extra shell weight are easy. Trouble begins when you go from 17 to 34 lbs, and it becomes an Olympic contest to lift a 3rd small panel on the same shell. Save the money, buy one "solid-framed" panel to go with more costly 2x flex.

[klpauba]

Definitely DON'T do anything like that! Those "Stayput" clips require you to pierce the shell - which was easy for the boater with fabric, and possibly necessary because the fabric can wear out over time and flap around in strong winds - but a terrible thing to do to a TM shell, which is solid, stable, and waterproof (unless you "screw it up" on purpose).

Although I have a number of different ideas for mounting that I have to think through, none of them involve putting holes in the roof. In this case, I was thinking of gluing the track to the roof (with VHB tape) and then having the stayput clips mounted to the track.

That's another reason to prefer two flex and one "solid" - with double flex panels, you mount the solid-framed panel above the midline, and you don't have to worry about the bump at all.

Ahhh, that makes a lot of sense! All in all, I have to admit that the one glass and two flex is the way to go (at least for me, anyway).

[klpauba]

And, I speak from actual experience in INTENSE sunlight (altitude 9000 ft). My aluminum-framed panel surfaces, with air underneath, get much hotter than the flex panel surface.
This is really good to know. My thoughts of adding a polycarbonate sheet (with integral air channels) would be unnecessary.

[rickst29]

By the way - the tape which I recommend for the flex panels (and the framed-panel mounting feet) is 3M "VHB" version "RP32", width 1". You'll need about 260 inches to handle the two flex panels, plus another 16 - 24 inches for the "solid" panel (16" using 4 mounting feet, 24" if you add another pair of feet as "overkill"). The total is a bit more than 7-1/2 yards, so you'll need two 5-yard rolls.

"RP25" is also usable, but a bit thin - the roof shells do need a bit of "flex", especially while dropping them down and clamping them in for travel. Thicker versions, in my opinion, have a bit too much sideways flex, and reduced "shear" strength, and don't transfer heat to the TM roof quite as well. (Therefore 4941, at 45 mils, seems a bit too thick.) In practice, though, all 3 thicknesses would work fine.

Since neither the flex panel bottom sheets OR the TM roof allow humidity to reach the middle of the tape, I would buy a set of the "primer" sticks too. Clean your tape surfaces really well - first a grease-cutting cleaner, and then take off cleaner residue using slightly watered-down IPA. (At about 50% water, 50% alcohol- the bottles start at 70% IPA, so you're adding about 1/4 as much additional purified/distilled water into the mix). Then the primer, then the tape segments. To make it easy, I used multiple short segments, and didn't try to do the entire length of my Flex Panel with a single piece. I started with the Flex panel loosely rolled up - unrolling the panel, sticking on tape segments, and pressing it into the roof in 3 segments, rather than juggling the entire thing at once.

[klpauba]

Is it enough to test new solar panels for the open circuit voltage and short circuit current only or should I bother getting a 100 W rheostat and check it (by ploting the power curve) under varying loads?

[scrubjaysnest]

I just check for Voc, open circuit voltage and Isc. Isc is the hard one as you'll need full sun to get close and it may be better if ambient air temp is 80 deg F or lower. Any kind of good sun will let you get Voc readings. For the short circuit current I figure with full sun any value greater then Imp is close enough.

[rickst29]

Test the output on the driveway before removing the plastic "protective film" which they add on top, to prevent shipping damage. Solar panels are not damaged by connecting through loads with near-zero resistance, so you can test both Voltage and Amps with a cheapo multimeter. (Just connect the meter itself across the two terminals, as the only load). The resulting Voltage should be quite near V(oc).

But: With the protective film still on, and later-winter sunlight conditions, expect the Amps to besignificantly be lower than I(mp). I'd expect to see V(oc) * I(sc) to calculate only about 50-60 watts from 100W "flex" panels at this time of year, with the "film" still attached.

The glass panel CAN have the protective cover completely removed for test before mounting - though of course, with all panels, tape a BLACK garbage bag on top of the entire cell surface after testing, while you take them up to the roof and wire them together. Don't forget, your configuration is wired in Series. Ignore the "danger! danger!" graphic at the bottom of the Ebay item I pointed to earlier - it doesn't apply to you.

After connecting the MPPT monitor the MPPT, the Battery RTS to the MPPT, and connecting the two "long" wire ends into the MPPT "Solar +" and "Solar -": Connect the "+" and "-" battery wires from MPPT to the batteries. The MPPT (and it's monitor) will power up. Now modify battery parameters in the MPPT to match your brand of batteries.

Be sure to MARK your two long wire ends as shown at the MPPT, "+" and "-", before routing them. From MPPT location to the outside, then up to the roof using one of the the lift arms - with a little "extra" length to handle changes in distance from shells-down to shells-up) Then connect as follows:

MPPT Solar "-" -----(long)----> Flex-1 "-". then
Flex-1 "+" to Glass "-". then
Glass "+" to Flex-2 "-". then
Flex-2 "+" -----(long)-----> MPPT Solar "+"

The take off your plastic bags, and verify total voltage (at the monitor) for the Solar array is about 53V. If that part worked correctly, then you're ready for it all works, then you can
Done right, after you make your final connection on the Solar circuit and when you take the bags off and turn on the Fridge to eat some power: About 53 Volts on the "Solar" side. That's the sum of V(mp) for the 3 panels.

That's the end of the job for Solar alone.
If you're crazy, magical "switching" of Solar versus boosted TV power could be added later - using the single MPPT controller, and a carefully selected Relay.

[klpauba]

Thanks for the replies, scrubjaysnest and rickst29!

While I just wanted a plan for checking new panels, all of the additional information will help me to get them hooked up right. I'll let y'all know when I get the panels in and will share with you my test results.

I remembered today that my dad has a nice "carbon pile" (I think that's what it's called) that he used to load test batteries and alternators. I was going to use that to help test the panels although it never even occurred to me that the spring sun is much less intense. With the information you provided, I'll just do a preliminary check and then rely on the MPPT to give me more detail when summer is here.