Adhesive advice for Solar panels

Foggy:
....* Better in warm solar cell temperatures (45* - 75*C = 113* - 167*F !!!)
[ Keep those panels cool? Why?]
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Cooler temperatures give more output. Generally solar panels are rated at 77* F (25* C), Each manufacturer will have a curve for the temperature vs output. For example:

Sharp Solar Panel NU-U230F3 is -.485% per 1 degree Celsius. So, for every degree above 25°C, the maximum power of the Sharp solar panel falls by .485%, for every degree above, it increases by .485%. Your panels may vary.

Dissimilar solar panels wired in parallel: you want to be sure that they are of the same voltage, and characteristics. Generally this means the same manufacturer as well as the same type of cells. If you wire dissimilar panels in series, they need to have the same current output, or they will be dragged down to the level of the lowest panel. If you are wiring two 12 volt dissimilar panels in series, you will have to use a MPPT controller, to get the 12 volts (instead of the 24 volts [actually more]). When you wire in series, you add the voltages, in parallel you add the current to get the output.

Thus, I would suggest that you use two similar panels--both voltage and current.
Hopefully you can find two 70 or 75 watt, 12 volt panels, which have the dimensions which allow you to use space most effectively. One trick I have seen is to mount the panels so that they can be hinged or articulated to both give the best azimuth, and use the space most effectively, rather than lying flat on the cabin top.

For example C Puffin has two panels on a SS pole which move in 2 planes;
C_Puffin_and_Grace_Full.jpg

The panels can be single mounted on a articulated mount, on a short piece of SS tubing, or even on a railing...Many options. For example you can get a 26.57 × 30.47, 70 watt panel. Maybe one on each side. You can put slightly off the roof on short or even fold down (think the 1: SS radio antenna ratchet mounts, which you can easily thread a 1" x 12" SS tubing onto, and then thread a ball mount for the panel on the top. When cruising, you can set the angle of the panel for optimal output. When trailering, or storing, down, but still close to horizontal to get very good output if desired.

Here is a link to custom made systems, similar to what I suggested.

1453433637.png These are fairly expensive, they can be made for much less. Got me thinking--maybe something like my "Commode" mount using Home Depot pieces... :lol:
 
After mix-'n-matching, using various combos of panels for my space,
I agree the best choice for my plan is 2 semi-flexible 55W panels from same Mfg.
same everything else.

Still no answer, except Greg, on whether to connect 2 panels in parallel or keep
them separately wired each with their own controller. Irregardless of how they are
wired, each panel will be subjected to unequal radiance (shade variations, on
curved pilothouse). I am tempted to wire them separately and let them each do
their own thing the best they can without one good performer being dragged
down by the other in shade or less optimum angle to the sun.

If panel cooling is so critical, why does Go-Power allow their semi-flexible panels
to be mounted with adhesive directly to a metal RV top (no spacers or relief
underneath)?

I'm a fix and forget with panel mounting on the pilothouse and forgetting about
tracks or poles for moving them around for best sun angle, etc. This may appeal
to others but not my cup of tea. Too many other (appealing) things to do.

Thanks again, Bob.

Aye.
 
If you want the simplest answer--wire each 55 watt panel separately to the battery bus system with a PWM controller appropriate for that size panel.

If I put solar on my boat, I would put two 100 watt panels, with articulation mounts, bypass diodes in the panels, and both wired MPPT controller.

Over 90% of RV owners today, use MPPT and wire all of the panels thru the one controller. They buy panels with have bypass diodes, which will minimize the effect of shading when wired in parallel.

I have no ideas why Go-Power allow their semi-flexible panels
to be mounted with adhesive directly to a metal RV top. It is going to be a little less efficient. But I suspect that they want to sell more panels, and it is easier to install that way without putting holes in the roof so people buy them.

I have a single 200 watt rigid panel, on my RV, to 6 Golf cart batteries. I use an MPPT controller, sized so I could put 2 more panels 200 watt on the roof, if I wish. The problem is that we find often we are in shaded camp sites if we are boondocking off the grid.. So even if we had 600 watts of solar panels, it would not provide us enough power to run 22 cu foot household refrigerator. If we don't have solar power/grid power, or are on the road (where the 200 amp alternator does fine), we run the generator and 140 amp battery charger about 4 hours a day.
 
Pat Anderson":1j2pin0f said:
Lots to think about here! I need to investigate SNAD and 1"x1" aluminum tubing with double stick tape to move my panels off the "wings" up to the roof so they can be flat to the sky. Now we do not have the Alaska Series, the panels need to move to the roof!
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While your moving your panels around take one of them and point it to the sun and watch your Victron I think you will be amazed at how power just one of your panels will generate if they are aimed correctly. Even if only one of them was adjustable you would get tons more power.

IMG_0246.jpg

One of these 30 watt panels will just about keep up with the new fridge and the second one puts me way over the top. Most of the time at Powell I move every day so the motor will make up the lost amperage. If I sit in the same spot for a while I can put out the panels and make my power. The new fridge is impressive and I still some more testing to do and I'll post the results.
 
A few posts back the discussion was about solar controllers and where does the electricity go when the battery is full. Then I saw that somebody had a hot water heater on their boat. Is it a 12V hot water heater? I have a couple of 12V hot water heater elements (fits the standard opening) from past projects. That might be something Brats with hot water might want to think about. Don't let that solar power go to waste. Heat some water.

Mark
 
I don't use the "load" setting, or have a water heater or any other official way to use otherwise wasted power (by which I mean afternoon when batteries are already back to 100%). But I do have ways of using it. This is when I charge things (computer, AA and AAA batts, tablet, phone, power tool batteries) and/or do things that use power that I might as well do at that time anyway.

Not that I don't charge and do things at night (definitely do, as a night owl), but it's just that I keep in mind when I do and don't have excess power. In a similar/opposite vein, if it's morning and I'm in the absorb stage, I won't likely choose that time to start charging big things (that would knock it out of absorb; sure it would go back later, IF the sun was still out, etc.)

This isn't to say I watch it like a hawk, or have to super-worry about it; but just that all else being equal, I'm there, I have the time, etc. --- I don't just *ignore* where things stand in the charging cycle.

That works well for me because water heating is a small part of my daily life (and I do it on the stove); whereas things like computers, tools, and AAA batts are more frequently used.

(The big draw, the refrigerator, just gets to do its thing.)
 
This wasted heat brings up another (missed, forgotten, not mentioned, probably
not believed) point about the difference(s) between PWM and MPPT charge
controllers (see UTube, my authoritative scientific source).

When battery charging is complete and the circuit is open (between the panels
and the charger), the PWM charger apparently dissipates the charge coming
from the panels as wasted heat. Probably not enough heat for a shower.
Makes sense as the panels don't know the circuit is open since it is in the
controller and the panel cells still have solar energy (perhaps) + amorphous or
poly crystalline or slim film silicone - everything a solar cell could want to do
its thing.

The more complex and efficient MPPT controller uses the energy from the panels
at open circuit time to convert this energy into useful amps (aka 'the boost', or
part of 'a boost'). Hence, part of the higher price tag. You get what you pay for;
no free lunch.

And on it goes...

Aye.
 
Maybe I should have added that I use an MPPT controller. I have never had a PWM controller, so can't comment on any differences beyond just what anyone can read in the manuals.

I can say that although there can be times when potential power is not used (say the batteries are at 100%, the refrigerator is off, and I'm not charging anything), and at those times the controller doesn't heat up, and I don't notice the panels getting any hotter than normal (of course black panels in the sun are always going to be hot).

The meter on my solar controller shows me the temperature of the controller and of the battery bank. The controller never heats up in any notable way. For the panels I'm just going by the fact that I handle them (when on land I sometimes move them or change the angle).

This is getting beyond my experiential knowledge and more into theory, but I remember reading something about how solar panels are not really "power providers" but instead provide current. Does that have something do do with it? For my uses they are the same (amps), but in the dark recesses of my mind there is something that says it matters in some way. Again, I only know how to wire them (avoid voltage drop, fuse properly, match volts in parallel and amps in series, etc.) and use them (set solar controller parameters, etc.); the electrical theory details are not all understood by me (current vs. power, etc.).
 
thataway":3gs878dg said:
How many watts are your water heater elements? Most are 1200 watts for the standard heater. That's a lot of power....
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The smallest one that I have is 300W. I have another one somewhere that is 1,200, but it has two elements on a single fitting, so it can be wired for 600 or 1,200. The little one is 25 amps at full tilt and will boil a gallon of water in short order (so it would require a thermostat if in a small tank). The idea is that any excess solar, even if it only heats the water in a 40 gallon tank 20 degrees is "free energy" if the alternative is just shutting down the panels when the batteries are full.

I played with the smaller one a little for possible boat application on my 16. It got more complicated than what I need. I don't really need hot water on demand. My little solar panel (4W), when connected directly to the little element, only got water slowly luke warm, not worth messing with. If connected to my battery bank, it heated like crazy. I would need a thermostat. But the biggest worry was having an electrical drain that exceeded my alternator output. Losing juice even with the engine running makes me nervous, especially when my induction burner can heat the little amount of hot water that I need and stay within alternator production.

Mark
 
Would love to find out how your system preforms under real world testing. I just picked up a big old version of your freezer. When fishing using dual screens electric downriggers and radar I feel like we are taxing our battery/alternator combo. Be nice to have significant solar work confidence it will keep us topped up!
 
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