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Old 02-03-2015, 16:25   #1
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Realistic Solar Panel Output in Carribean

i have four Kyocera 140 watt panels wired for 12 volt and 4 Seimens 75 watt panels wired for 12 volt - all going into a flexmax 80 charge controller.- these then go to my house battery bank of 4 8D AGM batteries- all panels are mounted flat with no provision to tilt toward the sun but they have no shading issues, excellent cooling, and the wire gauge is several sizes larger than needed to avoid voltage drop- taking a SWAG, what should these panels produce on a decent day in amp hours-- ( not the best not the worst) ? When you give your answer it would help if you let me know what factors you considered. Thanks
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Old 02-03-2015, 16:55   #2
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Re: Realistic Solar Panel Output in Carribean

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i have four Kyocera 140 watt panels wired for 12 volt and 4 Seimens 75 watt panels wired for 12 volt - all going into a flexmax 80 charge controller.- these then go to my house battery bank of 4 8D AGM batteries- all panels are mounted flat with no provision to tilt toward the sun but they have no shading issues, excellent cooling, and the wire gauge is several sizes larger than needed to avoid voltage drop- taking a SWAG, what should these panels produce on a decent day in amp hours-- ( not the best not the worst) ? When you give your answer it would help if you let me know what factors you considered. Thanks
Where are you and what time of year? It makes a big difference.
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Old 02-03-2015, 17:06   #3
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Re: Realistic Solar Panel Output in Carribean

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Where are you and what time of year? It makes a big difference.
I'm guessing from the title he's in or going to be in the Caribbean.
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Old 02-03-2015, 17:13   #4
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Re: Realistic Solar Panel Output in Carribean

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I'm guessing from the title he's in or going to be in the Caribbean.
Belize in the rainy season is a whole lot different than the ABC's in the dry season. The sun angle in Cuba in December is about the same as Maine in June, but the days are shorter in Cuba in December than in Maine in June.
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Old 02-03-2015, 17:20   #5
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Re: Realistic Solar Panel Output in Carribean

860 watts * 6 hrs *70% /12volts is 300ah. No shading will make a lot of difference. On a sunny day.
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Old 02-03-2015, 17:59   #6
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Re: Realistic Solar Panel Output in Carribean

We have 560 watts of solar and there is only a short period of time in northern Florida during the deep winter (like maybe 3-4 weeks) where we need supplemental power. We typically use about 140 amps (winter) to 180 amp (summer). In Key West over xmas and new years (we spent a little over a month there) we never started the engine or the generator to charge the batteries.

FYI - we have shading pretty regularly but we also have a wind generator that produces about 10 to 20% of our daily consumption. Our batteries are fully charged at minimum 3 times a week if not 6 or 7 when its sunny. We also do not have the benefit of the more efficient AGM batteries. We use trojan flooded.

I playing with the idea of removing a solar panel. I'll decide after this summer in long island sound.

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860 watts * 6 hrs *70% /12volts is 300ah. No shading will make a lot of difference. On a sunny day.
I'm not sure that is quite accurate. We need to get the batteries to 14.8 volts to be fully charged, so the chargers are set to 14.8 volts. It would look more like this:

860 watts * 6 hrs *70% /14.8 volts is 244 ah

The OP would substitute whatever voltage he needs instead of 14.8
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Old 02-03-2015, 18:26   #7
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Re: Realistic Solar Panel Output in Carribean

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860 watts * 6 hrs *70% /12volts is 300ah. No shading will make a lot of difference. On a sunny day.
That seems a little optimistic im my experience. I would use 50% where you used 70%. I have 300 watts and the very best day I ever had was 75 amp hours. I probably average 55-60. I do have a little shading issue early and late in the day. Boats at anchor tend to face east in the tropics, sometimes a bit north or a bit south but usually east. It's a unique installation if he has no shading issues at all.
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Old 02-03-2015, 18:34   #8
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Re: Realistic Solar Panel Output in Carribean

Sure, pick your multiplier. He said no shading -- that's big. And he said in the Carib, so the sun is strong and overhead. I said sun, no clouds. So maybe a little higher than your 50%. I also limited it to 6 hrs, but will get some for more hours than that.
The nominal 12v is just that. nominal. The bulk charge is done mostly at 13.x, the final acceptance is at 14.x. Pick an average. Watts is probably a better way to look at it, i.e. voltage independent, just power.
Either way, it is SWAG as asked for by the OP.
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Old 02-03-2015, 18:37   #9
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Re: Realistic Solar Panel Output in Carribean

Madehn,
In the days before MPPT controllers, the general rule-of-thumb for an "annual average" was....

Total array wattage x 1/3 = number of A/H's per day of daily power generation, for flat-mounted panels in tropical areas....
(this was assuming no shading, adequate airflow, etc. within 30* of the equator...)

This was of course exceeded in the summer time and of course less in winter time...

For your set-up (560 watts of Kyocera panels and 300 watts of Seimens panels) of 860 watts, this would give you about 290 A/H per day of generation...
Quote:
Originally Posted by Madehn View Post
i have four Kyocera 140 watt panels wired for 12 volt and 4 Seimens 75 watt panels wired for 12 volt - all going into a flexmax 80 charge controller.- these then go to my house battery bank of 4 8D AGM batteries- all panels are mounted flat with no provision to tilt toward the sun but they have no shading issues, excellent cooling, and the wire gauge is several sizes larger than needed to avoid voltage drop- taking a SWAG, what should these panels produce on a decent day in amp hours-- ( not the best not the worst) ? When you give your answer it would help if you let me know what factors you considered.
Of course cloudy days happen, so you could never count on that every day....but this was the general rule-of-thumb for cruisers in the Bahamas, Caribbean, tropical Pacific, etc...


Now, fast-forward to the early 21st century and MPPT controllers and you can get a boost to the current output (amps) of the system, and hence an increase in your daily A/H generation...

How much of a boost is a question I cannot answer with an absolute, but rather a "range"....10% is the minimum with 30% being the max (with depleted batteries and lots of good sun)....

So, with 860 watts of unshaded solar, mounted flat, with good airflow, and a good MPPT controller....you could get as much as 350 - 360 A/H's per day of generation....during sunny days, and maybe more on sunny/breezy summer days....

But, for planning purposes.....I'd plan on 300 A/H's per day of generation.....and if you get more, you're really happy!!



Now, understand that I used the word "generation" specifically....as this does not mean that this will replace the same number of A/H's used per day....it will be close, as some of your solar power will be running the fridge/freezer during the hottest part of the day, and I suspect that if you have a watermaker, you'll also run that during the day (afternoon) when you have plenty of solar generation....
But, understand that actually replacing A/H's used from the batteries takes a bit more generation that just that same number used....(I generally figure on 10% - 15% more....but that's being conservative)


So, if you use about 300 A/H's per day, which is a LOT of energy for any cruising boat, you will probably be fine....as long as the sun shines!!

Not knowing your boat, your cruising plans, your energy consumption, etc. makes any further numbers just a guess....



FYI, to see real-world installation and results of my 520 watts of solar, have a look here...
Solar Panels
(in general, I get > 200 A/H's per day all year 'round....about 200 A/H's per day in December in S. Florida, about 250 A/H's per day summertime in the N. Atlantic, etc. and even 230 - 240 A/H's per day in Nov / Dec in tropics....from 520 watts of unshaded solar with good airflow...)





To sum up...
Realistically figure on an "annual average" of about 300 A/H's per day (and most probably 10% - 15% more) of energy generation from your 860 watt solar array...


I hope this helps...

Fair winds...

John
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Old 02-03-2015, 18:57   #10
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Smile Re: Realistic Solar Panel Output in Carribean

Thanks for all the help! I have a D400 mounted as well so i should be golden for the amount i need- we have a big boat and i promised the admiral that she would not have to worry too much about power!
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Old 02-03-2015, 19:45   #11
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Re: Realistic Solar Panel Output in Carribean

Just fyi, at latitude 38, I get a max. of 60% or rated amps, though that drops to 50% as the angle of the sun and the boat swings at anchor.. This with cheap 12v panels and a PWM charge controller. So with 330 watts of panels, I get about 200 watts out of them from 11am-3pm.

The output might be bit higher in the tropics, but panel temperature coefficient will drop voltage as the panel gets hot.
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Old 03-03-2015, 10:47   #12
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Re: Realistic Solar Panel Output in Carribean

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Thanks for all the help! I have a D400 mounted as well so i should be golden for the amount i need- we have a big boat and i promised the admiral that she would not have to worry too much about power!
We have solar and a D400, and thought we'd be golden as well, and just got a portable generator to be sure. Depending on where you're anchored, you might not have solar until almost mid-day and no wind.
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Old 03-03-2015, 11:22   #13
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Re: Realistic Solar Panel Output in Carribean

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That seems a little optimistic im my experience. I would use 50% where you used 70%. I have 300 watts and the very best day I ever had was 75 amp hours. I probably average 55-60. I do have a little shading issue early and late in the day. Boats at anchor tend to face east in the tropics, sometimes a bit north or a bit south but usually east. It's a unique installation if he has no shading issues at all.
I believe Bill has nailed it. A hypothetical question with so many variables has no answer.
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Old 03-03-2015, 11:55   #14
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Re: Realistic Solar Panel Output in Carribean

I would expect something in the range of 40 to 50 Amps available.

I have found multiplying factor of 4 to 5 work fine while we were there (3 different times, each case was the winter sun). I think summer may be more overcast (?).

So, in Ah terms, assuming an empty battery, or a heavy load, say maybe between 150 and 250 Ah per day.

Thinking battery charging only, unless you are on the Lithium wagon, perhaps 100 Ah into the bank.

I think, because of the unpredictable pattern of sunny and overcast days, it is best to go over the top with capacity and have a side-load option for all those days when you make "too much" - a freezer, a watermaker, etc., anything that would make good use of the extra juice you get on the sunny days.

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Old 03-03-2015, 12:40   #15
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Re: Realistic Solar Panel Output in Carribean

On a good day (sunny and with a north blowing so that the panels get sun all day) my 290W panel with do 100AH

So on the same good day the OP could get 300AH from the solar ............... IF the batteries allow for current or there is some other load to use the power.

The batteries/daily use will determine how much you really get. Most days my panel does around 60-70AH because by mid day the batteries are charged and the panel is only supplying a little charge current plus whatever I'm using at the time.
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