More on solar panels. - Page 4 - SailNet Community
Old 03-30-2008
Sailor

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Quote:
Originally Posted by camaraderie View Post
Plumper...I will try one more time.
You did not give both VOLTS and AMPs taken at the exact same time.
If you do that and are using accurate instruments and measuring properly...then you multiply them together the result will never be more than 48.
It is physics and OHM's law...you don't get to play around with that in this particular universe!!

As to sailaways remarks that you object to. This topic has been totally dealt with before in somewhere around 1000 posts where we did a lot of research, have excellent links and which provides an excellent grounding in the subject. I have better things to do with MY time than to provide the same high quality and throughly researched answer to the same question posed by newcomers who were not present for the first go round. Thus we provide a link for YOUR benefit instead of ignoring you.
If you have questions about what you read on the link or think of new ones, we welcome the opportunity to help. But don't ask me to re-write war and peace every time someone new asks the same question.
I am not asking YOU anything. You choose to answer my question that I pose to the sailnet world. If you don't want to write an answer, don't. Simple.

I understand Ohm's Law. What I don't understand is your application of it. 48 / 14.2 = 3.38 x 8 hours sunlight (very minimum) = 27 amps

That is not 1/3 of 48.

For me to get only 16 amps (1/3 of 48) I would have to have less than 5 hours of sunlight.

It is just math and mine is correct as far as I can see.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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Old 03-30-2008
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You need not worry about my future replies.

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'72 Pearson 36

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Wow all i did was ask a question about a particular solar panel and end up with fighting over how they work. I was here for the big solar/wind thread and did read most of it. I just figured id ask about the set of panels that i can afford.

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1972 Pearson 36 S.V. Distant Star
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Old 03-31-2008
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SVD...there was no problem with your question or the resulting responses to your question as it was new ground and helpful to you and others. Hope you got what you needed.

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Old 03-31-2008
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Oh go back to your political dribble...you ...you... bearded grandmother of grandmothers senior member sorta thing you......the same can be said for that too...What world/local problums have you not hashed and rehashed over there in the last 3 years...No no I dare say Sir...I beg YOU stop the madness...Dont you make me come over there..

I'll have you know....Were getting quite the charge out of this discussion thank you very much...

Quote:
Originally Posted by sailaway21 View Post
Is it possible that there can be more on solar panels than is posted here: effectiveness of solar & wind

There is no "more" on solar panels. In fact there's already enough on solar panels to bring Evelyn Wood to her knees. Please help stop the madness. Countless souls sacrificed marriage and the opportunity to see their children grow up before their eyes to publish this link on solar panels. And they are just crazy enough to do it again. That link again is: effectiveness of solar & wind. My advise is to cancel your plans to launch the boat on Memorial Day, you're gonna be busy until at least the 4th and maybe Labor Day.

Don't make me come back here!

Last edited by Stillraining; 03-31-2008 at 05:37 AM.
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Old 03-31-2008
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Window solar panels

I am looking for a manufacturer of solar panels built into windows, suggest you look at a German firm "asola-power", but they are in development whereas I have heard that a japanese firm is selling them for sunroofs. Anyone encountered this?
fair winds, seanseamour
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Old 03-31-2008
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Quote:
Originally Posted by seanseamour View Post
I am looking for a manufacturer of solar panels built into windows, suggest you look at a German firm "asola-power", but they are in development whereas I have heard that a japanese firm is selling them for sunroofs. Anyone encountered this?
fair winds, seanseamour
I couldn't find these panels - do you have a link?

By the way - when at my boat this weekend with Saildog we did some rather extensive looking at my system.

To refresh, I have a Kyocera 80w panel, 3 Optima blue tops with 210 total amp hours. I use a c-80 charge controller for that, and I am not plugged into shore power. My monitor is a Xantex XBM wired on a toggle so I can check house and starter banks.

On a bright day in March, 10% cloud, at noonish with the panel tilted 20 degrees out of plane I was getting 2 amps - the batteries were showing 12.9v and a 99.6% charge.
I re-angled the panel to closer to flat to the sun, and stangely enough dropped to 1.2 amps, 12.9v.
Two hours later - I was at 100%, reading 13.3v and 212ah of capicity, with .9ah coming from the panels. We assumed this meant I was topped off at 210 ah, the extra 2 showing was the capicity available from the panels.
I turned on my anchor light - ah in went from .9 to .2, then built back up over a few seconds to .9 - In short, absolutely dead spot on what should have happened (the light put a load on it, the controller read the load and allowed the panel to pick it up).

How's that for fun. I don't gete that every thing out there says 12.6v is the max. I've seen 13.9 on my monitor - with a load being drawn. I do know about overcharge and equalization - mine is disabled. I also know you can have a higher voltage showing - and it's a 'flash' voltage, not real, and it's supposed to drop as soon as you put a load on. My batteries stay over 13v for hours at a time.

Nuclear engineering?

and a big raspberrry to the solar stick thread - I've read every frigging post and most of the semi-demi-god Nigel Calder has written. Unless it's exactly the same as my question it's not, well, the same. Rasp'emberry, sloppy ones even.
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Old 03-31-2008
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"For me to get only 16 amps (1/3 of 48) I would have to have less than 5 hours of sunlight."
And that's the reason to read the other, older, longer threads. They touch on the difference between amps and watts and amps and amphours, and the fact that "sunlight" is not a fixed or even quantity but one that varies through the day and latitude. And that variation is well known, well-documented, and detailed in the URLs in some of those other articles.

The bottom line is that you need to measure POWER in WATTS not volts or amps alone. And with a loaded circuit (i.e. normal connections) you will see the POWER form a solar array rise closer to local noon, then drop a bit towards 2PM, then plummet somewhere between 3 and 7, depending on the time of year. You'll see about a 10% climb/falloff per hour during the day, outside of the two noon hours, no matter where you are or who has promised you better, with fixed panels.
Add it up, divide the numbers, and it always comes back to "Panel wattage rating divided by 3-4-5-6 coincides with actual panel output rating, in amp-hours at 12-13-14 volts. The exact numbers don't matter, the relationship stands as a general back-of-the-envelope one that will accurately predict performance.
Why does this work? Because panels are all substantially the same, sunlight is all substantially the same, and the only variables (lattitude and time of year) are also about the same all over the world. The 3-4-5-6 numbers are a FUDGE FACTOR. That is, they are chosen--they are the product of the human imagination--because they make the equations work and work consistantly. You take the panel wattage, you multiply by lumens of illumination or however you want to measure sunlight per square meter of panel, factor in atmospherics, height, temperature, angles of incidence...Sure, you can do all that the same way the labs do. And it comes back to "Just divide by four or five" gives you the same result.
But of course, you are welcome to follow the posted URLs, or rediscover them yourself, and do all the math, and when you're done...you'll discover the same fudge factors still work the same way.

Last edited by hellosailor; 03-31-2008 at 11:29 AM.
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Old 03-31-2008
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Chuck...
"I don't gete that every thing out there says 12.6v is the max. I've seen 13.9 on my monitor - with a load being drawn. I do know about overcharge and equalization - mine is disabled. I also know you can have a higher voltage showing - and it's a 'flash' voltage, not real, and it's supposed to drop as soon as you put a load on. My batteries stay over 13v for hours at a time."

By 12.6V...I assume you are commenting on the voltage of a fully charged 12V battery at rest. I believe this is really 12.66V but close enough for government work. You can ABSOLUTELY get voltage readings of higher than 12.6 volts on a recently charged battery and it can take from 12 to 48 hours for readings to fully drop back to 12.6V. This is called a surface charge and reflects additional electrical charge stored temporarlily on the batteries positive plate after charging and does not reflect the actual storage capacity of the battery.

Removal of the surface charge is necessary to check a batteries natural standing voltage. For a 100 amp battery...you can accomplish this with a 25 amp load for 30 seconds. (Extend the time or increase the amp load for larger banks.) Small house loads will not do the job of dropping the Voltage back quickly. Hope this clarifies the issue.

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Old 03-31-2008
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Quote:
Originally Posted by camaraderie View Post
Chuck...
"I don't gete that every thing out there says 12.6v is the max. I've seen 13.9 on my monitor - with a load being drawn. I do know about overcharge and equalization - mine is disabled. I also know you can have a higher voltage showing - and it's a 'flash' voltage, not real, and it's supposed to drop as soon as you put a load on. My batteries stay over 13v for hours at a time."

By 12.6V...I assume you are commenting on the voltage of a fully charged 12V battery at rest. I believe this is really 12.66V but close enough for government work. You can ABSOLUTELY get voltage readings of higher than 12.6 volts on a recently charged battery and it can take from 12 to 48 hours for readings to fully drop back to 12.6V. This is called a surface charge and reflects additional electrical charge stored temporarlily on the batteries positive plate after charging and does not reflect the actual storage capacity of the battery.

Removal of the surface charge is necessary to check a batteries natural standing voltage. For a 100 amp battery...you can accomplish this with a 25 amp load for 30 seconds. (Extend the time or increase the amp load for larger banks.) Small house loads will not do the job of dropping the Voltage back quickly. Hope this clarifies the issue.

Absolutely, couldn't remember the term 'surface charge' (I said 'flash').
I didn't realize it needed to be hit that hard to flush it. I'll flip on the windlass next time, run some chain down and up for 30 and see what it says then.
Thanks.
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