Solar Enough ?

[Mark Johnson]

Originally Posted by djmarchand

Mark:

You must be in a high lattitude location. My experience is that 100 watts of solar panels will put out 33 amphours of 12V DC on a full sun day with a flat panel in the summer at moderate lattitudes.

Medum density overcast drops the output to 1/5 or less. It may be that your diodes improve your low light performance if the low light intensity results in a low enough voltage. The lower voltage drop of the Shottkie's will help this.

Actually our panels are 15 years old, and the numbers I quoted of what we "normally" get in a/h, is an average of over the 15 years, 12 full time only home and from the upper Chesapeake to the Rio Dulce to Trinidad. Thousands of nights on the hook.

Bear in mind, that when I quoted 60 a/h as a max, I should've been more clear. That was actually 60a/h max "going into the batteries", (as read by our Link 10 battery monitor) It was not taking into account that that was the left over amps, after what the refrigerator used that sunny part of the day.

So, they actually "produced" 60 a/h + about 15 a/h that the reefer and perhaps stereo used. Although only 60 a/h "went into" the house batteries.

For us, the Shotkey Diodes in each panel's + wire, caused <.5v of a volt drop from our 19v panels. (Minimal loss) What we got for this, was no more backflow into the more shaded of four panels.

For us, if the daytime sky was medium grey overcast, (VS really black and almost dark), we got pretty close to 40 or even 50% of their normal output. Only on the very darkest of "black angry sky" days, would our output go down to 25% of max output.

We even get some output when the Sun is touching the horizon, if I tilt the aft panel to face it. For that matter, the little LED anchor light creates a small bit of current.

I doubt that my diodes are making my panels better as much as our having such a wide spacing between the 4 panels, and the fact that their shading is minimal.

Mark

Thanks for pointing out my discrepancy BTW, I forgot that they were "running things", WHILE ALSO putting in those amps, that I read on the Link 10.

[Juniper]

Different panels have different power curve, some will put out good voltage, push, with low light, others will put out good amps, flow, problems happen when it has good amps but not enough volts to push it into the batteries, but then it's not making amps or power, or it could be helping to run thing, higher volt panels seem to work better, but if you don't have a MPPT you loss some watts that were advertised,

[barnakiel]

Originally Posted by Mark Johnson

This last statement just confuses me...

(...)

I wonder if our experience is really that different, or are these statements about solar "not working at all on cloudy days", more of an assumption, than verified?

(...)

"Shotkey Diode"

(...)

I owe you an explanation. Neither assumption nor verified. Simply my oversimplification that causes havoc.

By 'nothing on a cloudy day' I meant very little compared to a sunny day. Not nothing at all, just very little.

Our panels tilt and we normally adjust them for the best angle too, unless we are fully charged and in such a case we either use the energy somehow (e.g. charging all rechargeable toys) or just let it be.

Our panels came wired with the diodes in the box and the manufacturer recommended no further diodes.

Apologies for the unnecessary confusion.

PS I believe the diode is spelled "Schottky" (after the guy named Schottky) not "Shotkey" (?) or else it is another type of diode.

Cheers,
barnie

[barnakiel]

Originally Posted by Juniper

but if you don't have a MPPT you loss some watts that were advertised

Not in all cases.

If the batteries are huge and panels relatively small then you lose nothing. MPPT kicks in at best when the batteries are approaching charge. They are great choice for batteries that will be 'shallow' cycled.

However, given the cost of an MPPT regulatpor one has to think twice, as we can also get more Amps by ... buying bigger solar panels!

And bigger panels with an MPPT regulator would ... but let's stop day-dreaming ;-)

barnie

[Mark Johnson]

Originally Posted by barnakiel

I owe you an explanation. Neither assumption nor verified. Simply my oversimplification that causes havoc.

By 'nothing on a cloudy day' I meant very little compared to a sunny day. Not nothing at all, just very little.

Our panels tilt and we normally adjust them for the best angle too, unless we are fully charged and in such a case we either use the energy somehow (e.g. charging all rechargeable toys) or just let it be.

Our panels came wired with the diodes in the box and the manufacturer recommended no further diodes.

Apologies for the unnecessary confusion.

PS I believe the diode is spelled "Schottky" (after the guy named Schottky) not "Shotkey" (?) or else it is another type of diode.

Cheers,
barnie

Barnie,
Thanks for the spelling correction, it was never my strong suite, and spell check missed it too.

My panels also came with what they called "bypass" diodes that were more to prevent backflow problems within the panel. MY mfg. didn't recommend my additional Schottky diodes either, (which are for a different purpose), under the assumption that the power gain from prevented backflow to shaded panels, was less than the losses due to the small v drop that they create. If I had one panel, or a rack of panels in close proximity to one another, I wouldn't use them. I just reasoned that with my panels being so separated from one another, there was a higher likelihood of one always being shaded and the others not. This would make this VERY small point in my advantage.

The "Schottky" diode, is like any other one way diode, except it is known to have the least v drop.

I have used solar to power my boats since the mid 70s, and always used them, it became a habit I guess. I have no way to test weather my theories about their use are correct or not, because we're only talking about 1% more or less.

I'm so picky about these things, I spend the money and time in the "hopes" of 1% more efficiency. Who knows?

Mark

[barnakiel]

I will add a small drift here, PLS forgive and forget, and I think it is worth it.

I noticed that every time I pass a small cruiser on a dock nearby, their windmill is 'always' spinning. Now it is the small Rutland, the newer one (sharp nose).

I would not mention this as the unit has low output, etc.. Why I do mention is to ask if you guys think when the windmill turns slow - does it charge? I mean is the voltage enough, just amps very low?

If the voltage is OK then I think I will get such a unit soon - I walk, it is very light, and that bonky thing keeps on spinning! Amazing.

barnakiel (I am NOT a Rutland vendor ;-))

[Cotemar]

barnakiel,
The Silence is golden, did we say solar is maintenance free.

[Feral Cement]

Originally Posted by Mark Johnson

If you point your stern panels toward the setting sun on a pivoting rack, you can add a lot more amps, on a cloudy day.

Mark --

Where did you get that stern mount? I was think of putting a rotating stern panel on my Catalina 27, between two "davits" with knobs to tighten the panel into the best pivot position. Sources? Thanks!

John

[Feral Cement]

Originally Posted by rebel heart

- SensiBulbs for interior lights. We can have all our cabin lights on and we're using ~1 amp.
(big recommendation for SensiBulbs)

At $40 a pop, they oughta come with their OWN solar panel! Anyone have a second option, a bright LED cabin lightbulb? A part #, please.

Thanks,

John

[Feral Cement]

Originally Posted by Mark Johnson

For us, the Shotkey Diodes in each panel's + wire, caused <.5v of a volt drop from our 19v panels. (Minimal loss) What we got for this, was no more backflow into the more shaded of four panels.

Would a single panel eliminate the need for the diode?

John

[Bash]

Originally Posted by barnakiel

I will add a small drift here, PLS forgive and forget, and I think it is worth it.

I noticed that every time I pass a small cruiser on a dock nearby, their windmill is 'always' spinning. Now it is the small Rutland, the newer one (sharp nose).

I would not mention this as the unit has low output, etc.. Why I do mention is to ask if you guys think when the windmill turns slow - does it charge? I mean is the voltage enough, just amps very low?

If the voltage is OK then I think I will get such a unit soon - I walk, it is very light, and that bonky thing keeps on spinning! Amazing.

barnakiel (I am NOT a Rutland vendor ;-))

Does it say "Rutland 405" on the tail? If so, that's the trickle-charge model.

[Feral Cement]

Sorry to be a "thread hog" . . . .

A quick Google search shows me 200W for $456 or about $2.28 per watt. Any sources where I can do better? Any brands to stay away from for durability or output issues?

And what does the "beginners kit" look like? I'm thinking solar panel, mounting bracket/davits/system, wires, and a charge monitor. Anything else? Diode optional?

Thanks - Santa needs to know.

John

[Bash]

Originally Posted by Feral Cement

And what does the "beginners kit" look like? I'm thinking solar panel, mounting bracket/davits/system, wires, and a charge monitor. Anything else? Diode optional?

You don't need a charge monitor, but you do need a charge controller.

Having one of each is extra nice.

Don't get a diode until you've gotten the rest of the system. Many panels have diodes installed.

[Feral Cement]

Originally Posted by Bash

You don't need a charge monitor, but you do need a charge controller.

Having one of each is extra nice.

Is there a 2-in-1 combo model? Also, what's the cost for the controller on a 200W system?

Thanks, again,

John

[VirtualVagabond]

Originally Posted by Cotemar

I have 460 watts of solar panels and make more power than I need.
With the new solar panels that they have today, it's no problem.

I will just have to add more batteries if I see they are not keeping up on our overnight cruises.

Right now I have no problems. Batteries are always fully charged after 9:30 am.
We have LED lights on everything, mast, reading, heads, gages.

Also

CotemarRe: Solar Enough?
Today’s solar panels are truly magical. They pump out the power and are quiet and maintenance free.
After the first week we forgot they are even there.


Any particular brands and costs?

Vic