My last
boat had Arco, and it is now on a pond boat's wet
storage garrage roof. It is now about 23 years old & still works! My
current trimaran Delphys, has an 85, 35, & 55 W that are Siemens, and a BP solar that is 110W. I bought acording to what would fit best, of the better brands, 14 years ago when I installed them. They are all still working fine, but the edges of the crystals are showing some evidence of deterioration. In another 10 years, they may need replacement, but who knows. So far the BP Solar is holding up best. These
panels are not prone to sudden failure, (unless you crush it), but simply put out less as they age. I think that the warrenties were for within 20% of new, for 20 years!
You need a panel voltage of about 17 or 18V, (fairly standard), because the heat of the sun drops the voltage, and it must not get below say 15V if it is to have enough push to do the job. I recomend you search the "Back to the land"
cabin dwellers type catalogs or web page. The
panels on boats these days are "house" panels, and can't be walked on, (although I have stepped on them by
accident, without harm)... These panels last much longer than the old "Marine panels" from decades ago. This is simply because the sealing technology has come that far.
A 20 or 25 year warrenty is to be expected. You should use a 4 stage adjustable smart charge controler, and we also got ours from one of the above sorces. Our controler is 11 years old & works great! Since we usually have some of our 4 panels shaded, I did opt to install a "low loss
Shotkey blocking diode" on the + wire from each panel. (this reduces back flow from the sunny panels to the shaded ones, but reduces output a bit) IF your panel / panels are close together, and either all sunny or all shaded, I'd omit the blocking diode.
If you want to go 95% solar self sufficient like we did, (rarely run the engine), the best bang for the buck is to go as low energy as possible on the boat's gadgets. Vacuum panels on the small frige, don't make ice, LED
cabin &
anchor lights where possible, (fluorescents otherwise). Use the smallest "Power Survivor"
water maker, avoid the use of the boat's
inverter by NOT running AC wall "black box" items like TVs or
computers, off of AC. Look at the AC black box that came with the computer.... It will say something like 120V AC in, 19V DC out. In this case you can get (from a generic computer supply web site), a 12V DC in "step up" transformer, (With cigarette lighter
plug in wire, and the correct small computer or flat
screen TV power
plug out wire that is the appropriate 19V, (or whatever). It is also best to get 12 V (auto)
DVD players, and if you watch movies like we do through the sterio, make sure it is a 12 V sterio. By doing this, we rarely use the
inverter, which cuts the amp hours of watching a
movie for example, in half.
We have spent a couple of thousand nights on the hook, and our average is somewhere in the low 30 Amp Hrs / day. Our amp meter tells us the amps being put out, and the amp hours charged is actuslly a bell curve. However, on a sunny day, It averages out to at least the max output X 5 hours / day. So we could theoretically get from 50 to sometimes 60 amp hours / day. This means that we have our
batteries 100% FULL by noon or so on a good day. If it is overcast, it might take all day. You need to size the array for
TWICE your normal daily
consumption, to make up for cloudy days. IF you bring up your
batteries to 100% each day, (not practical with an alternator), The batteries will last twice as long! This pays for one of the panels.
We have our panels spread out to make it where if one is shaded, the others are not. A VERY dark line shadow like made by the
mast or boom, may cut the panel down to 20% of it's rating, but an extreemly overcast sky will usually only reduce the panels output to about 60% of it's rateing. (a very bright but cloudy "white out" day, may be 90% of max output!) A
radar arch, or
davits, or bracket like mine, are great for a big 110 W panel. (larger panels are cheeper / watt) IF you have a
wind generator on the arch & it shades the panel on ocasion, you would be far better off removing it and let the sun shine on the panels.
Our collective 285 Watt solar array, With our 2 @ 340 AH Trojan L-14 6V batteries (in series) works together perfectly for our normal daily usage. By cycling the batteries so lightly, they should last at least 10 years!
The panels need air flow under them, Biminis are a good place for a 90 W on each side, and if mounted to a cabin top like some of mine, the homemade "Starboard" side mounts, provide both ventilation & a "snag free"
installation. The articulating bracket on the back is great! Anchored out & facing the prevailing easterly winds, I can tilt it toward the afternoon horizon at 5:00 PM, and it will put out power untill the sun goes down. (on the rare occasion that I actually need the extra 8 amp hours)
NOW... The exception of this scenario is overnighters! We have cruised both sides of the
Caribbean, but guess we average only about 25 overnighters per year. On these 25 days, we may use 80 amp/ hours or more. That's what the
engine is for. The best time to crank the
engine is when the batteries are lowest. (when they can accept the 35 amps that our 55A
alternator actually puts out). We therefore run the engine for about 45 minutes, starting at 5:00 AM, then the solar takes over as the sun comes up. When we switch our tricolor light to LEDs, our
consumption may go down by 18 or 20 more Amp Hours!
That's about it. Spend the
money on
solar panels & conservation, or a much larger amount over time on house batteries,
diesel fuel, & a prematurely carboned up engine from running @ low RPMs.
Best, Mark J
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