"Walt" wrote in message ...
Im not sure the MPPT controller allows for higher voltage/smaller wires.
PV arrays are to some
extent constant current and a "12 volt" array will put out its maximum
power at a voltage
typically higher than the battery. So if you hook the array up to a
battery with a "cheap"
controller, it is basically a direct connection and the PV current stays
about the same but the PV
array voltage drops to the battery voltage so you can lose a fair amount
of delivered power. The
MPPT controller allows the array voltage to operate for maxiimun power
while supplying current to
the battery at the batteries charge current. I have a 160 watt pannel
(2x80w Kyocera) and
typically I might have 8 amps comming out of the panel and maybe 10.5
going into the battery (the
currents will of course vary all over depending on how much sunlight,
angle, ect).

Also, the MPPT charger I have (Blue Sky - company used to be called RV) is
intelegent about
properly charging the batteries which can make them last longer. Ive only
had this product for
several months but think it was a good investment.

wh

Blue sky was the make my installer (svhorizon.com, KISS US distributor)
recommended. It was his suggestion that I go to the higher voltage panels in
order to make for smaller wires possible with the same voltage drop (thus
the need for MPPT). As much wattage as we'll have, and as far as it has to
run to the ER, after the trip down the (tall) arch, drop is of concern.

Unfortunately, they're driving to the Oakland show and won't be available to
start on the project for nearly a month. Then, I hope to get the electrical
stuff buttoned up quickly, as I have what is now a very short window to get
the boat finished before my surgery.

L8R

Skip


--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

"Skip Gundlach" skipgundlach sez use my name at earthlink dot fishcatcher
(net) - with apologies for the spamtrap wrote in message
...
Hi, Y'all...

Well...

"Larry W4CSC" wrote in message
...

snipped bit was here
Hmm...5A from a big solar panel or 15A from a wind generator =
5X12hrs=60AH
per day if the sun shines or 360AH wind power in a full gale 24/7.

Not much of a real powerhouse, is it, huge batteries or small
batteries...

Plan on using the big alternator on the engine every day in this
configuration.

Hm. Help me with the math. As a lapsed math, physics and chem major, I
don't remember my stuff all that well. However, I'll have right in the
neighborhood of 500W solar, and a KISS wind generator in the Caribbean.
Various vendors suggest I take the wattage and divide by 3, or 4 if really
lousy weather, for a reasonable typical AH input, daily. My math has that
at 170-125AH/day, plus some other unknown - but apparently pretty
substantial - AH from a KISS.

Our anticipated daily budget is about 125AH; we'll have (for simplicity in
this calculation) ~1250AH capacity. It's our presumption that we'll have
4-5 days capacity, in the most unimaginable (in the Caribbean)
circumstance
of continuous no wind or sun.

Have I missed something here?

Hi Skip, I'm looking at your math and trying to work out how you came up
with 170-125AH/day generated by your solar panels.

Will this 500 watt panel array ever actually put out 500watts? Or, as you
said above, will it really be only a quarter to a third of this ? If so,
how many hours a day will this panel put out this kind of wattage? Perhaps
a couple of hours on either side of noon with diminished output before and
after this time?

500 watt panel /14.5 volt supply = 35 amps of current.
A third of this is only about 12 amps or so. For about 4 hours is 4 hours x
12 amps = 48 AH per day. Perhaps you will get some useful power out of the
rest of the available daylight, perhaps another 22 AH or so, that still only
gives you 60 AH per day or so, no? Which doesn't seem to come close to
filling your anticipated daily power budget, let alone leave anything to
replenish the batteries from the drawdown on cloudy days.

Perhaps I've missed somthing here?

More snipped bits

Thanks.

L8R

Skip (about to head back to the boat for another couple weeks, this time,
this part, of the refit)


--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"There is nothing-absolutely nothing-half so much worth doing as simply
messing about in boats.
In or out of 'em, it doesn't matter. Nothing seems really to matter,
that's
the charm of it.
Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do,
and
you can do it if you like, but you'd much better not."


--
Ken Heaton & Anne Tobin
Cape Breton Island, Canada
kenheaton AT ess wye dee DOT eastlink DOT ca

"Ken Heaton" wrote in
news:xh05e.4996$VF5.1702@edtnps89:

Will this 500 watt panel array ever actually put out 500watts?

Another interesting point is that a solar cell is very poor efficiency.
Here's a report on a new Sanyo HIT cell hitting 21.3%....

"The resulting efficiency level exceeds 21.3 percent, which until now, was
the highest level delivered by SANYO HIT solar cells. The HIT solar cell is
10cm square, nearly the same size as solar cells currently used for home
and industrial applications."

Regular silicon solar cells are like 6% efficient!

Even if we get this supercell technology, to get 500 watts out, we're going
to have to put 2500 watts of sunshine in and cool the cells of 2000 watts
of heat! Will that be fresh water or seawater cooling??...(c; Maybe we
can use the heat to cook lunch on the metal heat sinks...saving the drain
from the microwave oven!

Wonder why we can't run a little water pump in the loop to the water
heater? The waste heat from the solar charging could give us all HOT
SHOWERS AND DISHWATER!

The big panel on Lionheart puts out 5A on its best day and only if the boom
is out wide and not shading anything on top of the cockpit hardtop it
covers....

Hi, Y'all,

I'm getting a little out of my depth, my last physics classes having been
nearly 40 years ago, but...


"Ken Heaton" wrote in message
news:xh05e.4996$VF5.1702@edtnps89...
Hi Skip, I'm looking at your math and trying to work out how you came up
with 170-125AH/day generated by your solar panels.

I'm not so much doing that as passing on the conventional and experienced
(that is, by folks who have SPs installed) wisdom that one may take the
wattage of current technology solar panels and divide by 3 (typical) to 4
(cloudy, etc.) for a real-world daily AH result. Not having same installed
on our boat (where there will be minimal or no shading), I can't do more
than speculate.


Will this 500 watt panel array ever actually put out 500watts? Or, as you
said above, will it really be only a quarter to a third of this ? If so,
how many hours a day will this panel put out this kind of wattage?
Perhaps
a couple of hours on either side of noon with diminished output before and
after this time?

500 watt panel /14.5 volt supply = 35 amps of current.

Ah - but I'm going with the higher voltages, for a couple of reasons.

One is easier transmission - smaller wires - for the same voltage drop.

The other is for more flexibility when tied to an MPPT. Typical peak
voltage would be in the 30s. So, presumably, at least, more amps result.

A third of this is only about 12 amps or so. For about 4 hours is 4 hours
x
12 amps = 48 AH per day. Perhaps you will get some useful power out of
the
rest of the available daylight, perhaps another 22 AH or so, that still
only
gives you 60 AH per day or so, no? Which doesn't seem to come close to
filling your anticipated daily power budget, let alone leave anything to
replenish the batteries from the drawdown on cloudy days.

Agreed. However, that (your scenario above) would make for a very small
output. I believe the 3 or 4 divider isn't at any given minute - else, why
would they be rated at any given wattage? - but, rather, a full-day
experience, ameliorated by darkness, clouds, shadows, and other impedimentia
to a 24-hour, full output, result.


Perhaps I've missed somthing here?

I dunno - perhaps *I've* missed something in all the research I've done. I
could swear that various posters to these fora have provided real-world
experiences on which I base my assumptions, backed up by various vendor
claims (as taken with the requisite grain of salt).

That I'll be in the Caribbean has got to help, too, but it's not the
presumption with which I started.

L8R

Skip, home for a couple more days before - this time - a 4 week working
visit to the boat-on-the-hard

--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"And then again, when you sit at the helm of your little ship on a clear
night, and gaze at the countless stars overhead, and realize that you are
quite alone on a wide, empty sea, it is apt to occur to you that in the
general scheme of things you are merely an insignificant speck on the
surface of the ocean; and are not nearly so important or as self-sufficient
as you thought you were. Which is an exceedingly wholesome thought, and one
that may effect a permanent change in your deportment that will be greatly
appreciated by your friends."- James S. Pitkin

My 0.0002, could be wrong..

I have a 160 watt panel and when the sun is shining and the panel is aimed
right, and Im using an MPPT controller, Im getting reasonably close to 160 watts
out of it - like maybe 150..

What Ive seen are calcutions based on the rated power of the PV panel and
assuing that you get 5 hours of sunlight per day. On good sunny days, this
possibly underestimates the power. On cloudy days, you might get a lot less.
Using current to compare things is ok but it doesnt take into account voltage.
What really is important is power.

Here are some rough calcs..

At 450 watts PV power and assuming using MPPT (which works and improves
efficiency for either 12 or 24 volt systems), the output current at full power
is (power = voltage * current)

15 amps for 24 volts system (15 = 450/30 volts - assumes MPPT allows panel to
operate at 30 volts rather than battery voltage)
30 amps for 12 volts system (30 = 450/15 volts - assumes MPPT allows panel to
operate at 15 volts)

So if this current were available for an average of 5 hours per day, you would
have

12 volts system : 5hours * 30 amps = 150 amp hours
24 volt system: 5 hours * 15 amps = 75 amp hours

Note that the amp hours is different but the power is the same - which is why
you should really look at watt hours and not amp hours to see what capacity is.
The watt hours is then:

12 volt system: 5 hours * 30 amps * 12.5 volts = 1875 watt hours
24 volts system: 5 hours * 15 amps * 25 volts = 1875 watt hours

To consider what long wire runs do, a lot of PV runs use 10 guage wire which has
an impedance of "about" .00118 ohms per foot. So if you had for exampe 40 foot
of wire between the PV array and the battery, the resistance which disipates
power would be the combination of the two wires (ie, the total wire length is 80
foot) so the power disipating resistance of the wire is 2 * 40 foot * .00118
ohms/ft = .0944 ohms.

So the power lost by the long wires would be ( power = current**2 * R)

12 volt system: 30**2 * .0944 ohms = 84.96 watts
24 volt system: 15**2 * .0944 ohms = 21.24 watts

For long wires and higher current, the 24 volts system looks a fair amount
better to me. You would be loosing nearly 20% just by the wire if you used 12
volts with this system. MPPT will help and I think a good application here but I
personally dont think MPPT is about 12 or 24 volts - its about better utilizing
either voltage system.

I could be wrong or have bad calculation so dont take any of this seriously (and
Im sure someone can find something wrong with it..)

Wally Hall
Denver


Skip Gundlach wrote:

Hi, Y'all,

I'm getting a little out of my depth, my last physics classes having been
nearly 40 years ago, but...

"Ken Heaton" wrote in message
news:xh05e.4996$VF5.1702@edtnps89...
Hi Skip, I'm looking at your math and trying to work out how you came up
with 170-125AH/day generated by your solar panels.

I'm not so much doing that as passing on the conventional and experienced
(that is, by folks who have SPs installed) wisdom that one may take the
wattage of current technology solar panels and divide by 3 (typical) to 4
(cloudy, etc.) for a real-world daily AH result. Not having same installed
on our boat (where there will be minimal or no shading), I can't do more
than speculate.


Will this 500 watt panel array ever actually put out 500watts? Or, as you
said above, will it really be only a quarter to a third of this ? If so,
how many hours a day will this panel put out this kind of wattage?
Perhaps
a couple of hours on either side of noon with diminished output before and
after this time?

500 watt panel /14.5 volt supply = 35 amps of current.

Ah - but I'm going with the higher voltages, for a couple of reasons.

One is easier transmission - smaller wires - for the same voltage drop.

The other is for more flexibility when tied to an MPPT. Typical peak
voltage would be in the 30s. So, presumably, at least, more amps result.

A third of this is only about 12 amps or so. For about 4 hours is 4 hours
x
12 amps = 48 AH per day. Perhaps you will get some useful power out of
the
rest of the available daylight, perhaps another 22 AH or so, that still
only
gives you 60 AH per day or so, no? Which doesn't seem to come close to
filling your anticipated daily power budget, let alone leave anything to
replenish the batteries from the drawdown on cloudy days.

Agreed. However, that (your scenario above) would make for a very small
output. I believe the 3 or 4 divider isn't at any given minute - else, why
would they be rated at any given wattage? - but, rather, a full-day
experience, ameliorated by darkness, clouds, shadows, and other impedimentia
to a 24-hour, full output, result.


Perhaps I've missed somthing here?

I dunno - perhaps *I've* missed something in all the research I've done. I
could swear that various posters to these fora have provided real-world
experiences on which I base my assumptions, backed up by various vendor
claims (as taken with the requisite grain of salt).

That I'll be in the Caribbean has got to help, too, but it's not the
presumption with which I started.

L8R

Skip, home for a couple more days before - this time - a 4 week working
visit to the boat-on-the-hard

--
Morgan 461 #2
SV Flying Pig
http://tinyurl.com/384p2

"And then again, when you sit at the helm of your little ship on a clear
night, and gaze at the countless stars overhead, and realize that you are
quite alone on a wide, empty sea, it is apt to occur to you that in the
general scheme of things you are merely an insignificant speck on the
surface of the ocean; and are not nearly so important or as self-sufficient
as you thought you were. Which is an exceedingly wholesome thought, and one
that may effect a permanent change in your deportment that will be greatly
appreciated by your friends."- James S. Pitkin

In article xh05e.4996$VF5.1702@edtnps89,
"Ken Heaton" wrote:

Will this 500 watt panel array ever actually put out 500watts?

Yes, it will, and for the first few years, more. 34 amps times 8 hours
(and that's conservative) is 250 AH. Our little panel puts out its rated
power from dawn to dusk if I realign it from time to time.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Thanks for the real life info Jere. I've been wondering the same things as
Skip, but I will be using a much smaller panel. And Anon had some good info
on calculating power output. I'll have to go Google MPPT controllers now...
--
Ken Heaton & Anne Tobin
Cape Breton Island, Canada
kenheaton AT ess wye dee DOT eastlink DOT ca

"Jere Lull" wrote in message
...
In article xh05e.4996$VF5.1702@edtnps89,
"Ken Heaton" wrote:

Will this 500 watt panel array ever actually put out 500watts?

Yes, it will, and for the first few years, more. 34 amps times 8 hours
(and that's conservative) is 250 AH. Our little panel puts out its rated
power from dawn to dusk if I realign it from time to time.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/