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Kathleen-
For no good reason, I can deal with volts and amps. (Well, sometimes, and I still can't get my license for practicing mathematics over the internet, but that's neither here nor there, right?) For a boat your size, that solar mizzen mast probably scales in very nicely. No custom negotiating with tower welders and other techie stuff required, and I can see it fitting in very nicely there.
No matter who I ask...the best answer I can get about really accurately measuring amps and volts on a PWM-DC system seems to involve fourier transforms and other math that glaze my eyes and hurt my head. I confess, I never took calculus and if anyone has a good PBS-video-set to recommend on it, please do.
What I want to do, is actually deep cycle some battery power in/out with the SolarStik and make the measurements based on the DC from the batteries. Easier said than done, as I had to go out of town, came back to heat warnings, grabbed most of a good day and then ducked thunderstorms and (please, tell me this isn't Kansas) even TORNADO WARNINGS and I can tell you, until fairly recently I was sure I wasn't in Kansas and didn't know anyone named ToTo.
Cam-
"First I would note your reported 63 watts of output at peak (note how this contrasts with the claim of OVER 100 watts by Brian due to "special BP panels").
I'm not going over that 960+ message thread but IIRC it wasn't Brian but someone else who was claiming that wattage, and that may have also been someone who simply said watts instead of amps or watt-hours...I thought that had been cleared up?
My readings are from a good but not perfect day, with a UV index of 9 and temps in the 80's. If you can get a brighter day (which you can) and move further south (easily!) and cool the panels into the 60's instead of the 80's, you can raise their output every time. That's well documented and should be no surprise to anyone. BP only warrants the panels for 90 watts output, I could only measure some 63 under the conditions I had. I'd really like to retest them on a screamingly beautiful day--but don't know if I'll be able to command that kind of wx before the panels have to move on.
"I am having trouble following your math." Remember, I'm numerically challenged.
"That would be...about 250 Watt-hours up here, indicating 375Wh down there in sunnier climes. Or about 73 Amphours at 13.6V here, and closer to 100AH down there."
"How do you make that calculation...watt hours/Volts=amp hours NO? "
Right, should be.
"375 watt hours at 13.6V would generate...27 amp hours or so.
Am I wrong on this calculation or misinterperting what you've said. "
Your math is right, let me look back at the notes and see what I've screwed up now....OK, I see it. probably got interrupted by that telephone thing and dropped out a line. I was talking about two different things: Watthours as being the total daily output from the unit, so let me rephrase that and add in the missing part:
""That would be...about 250 Watt-hours up here, based on four hours of full output power, which is what a full day is usually equal to, indicating 375Wh down there in sunnier climes. Or about 73 Amphours at 13.6V here for the four midday hours, and neglecting anything outside of them,"
Does that read clearer?
The general literature and the URLs posted from the other thread all indicate that you can approximate the full daily power output of the panels (typically in watt-hours but however you please) by taking the output during the noon-to-one-oh-clock hour, and multiplying it by a factor for that location. Down south like the Florida Keys, that factor is about six. Up north here, it is about four. Those are rough numbers--but they are good ballpark numbers.
"If I am right and the panels when adjusted reasonably frequently could put out the 63 Watts you found for the equivilent of 10 hours a day...or 630 watt hours at 13.6 volts...that would be 46 amp hours. "
Nah. You can't get ten hours at maximum power. And some testing I did in dim light shows that while you can measure good voltage from the panels in lowering light--that's only into the high resistance of the voltmeter. Hook up a real load of any kind, and the output plummets down to 4-6 volts real fast, the panels are useless in the light we see here at 7AM. To give you some comparison, using a classic lightmeter the 6:30AM light was around 65 foot candles (I know, an obsolete standard but one I prefer) while noontime daylight is something like 32,000 foot candles.
Considering that the amount of power (sunlight) available to the panels changes by a factor or 32,000/65, naerly a 500x change in the amount of sunlight and power going INTO the panels, there is no way the panels are going to put out more than 1/500th of their full power at 6:30AM. Ain't gonna happen unless aliens on a UFO are beaming lasers into them. Even the light at 8AM was not enough to generate any power into any load attached to the panels. So, anyone who thinks the first and last two hours of sunlight are going to generate power...better flag down that UFO.
The light level readings I got, measuring incident light (i.e. that falling on the panels) was:
5:30AM, 12 foot candles
6:00 AM, 32 foot candles
6:30AM, 65 foot candles
7:15AM, 130 foot candles
8:10AM, 260 foot candles
and then I was in motion and didn't get a chance to measure again until somewhate after 10AM, at which point I had "noon" daylight, a full scale reading on the lightmeter, a classic Gossen LunaPro. Not calibrated to anything in many years but a reasonably accurate if archaic device.
"Are you measuring watt/amps/volts off the panels or only at the "end" of the system." Both ways. I measured at multiple times, and in order to reality check things I plugged the meter into the output of the stick directly (at the input of the controller) and the output of the controller. I read the amperage via the current shunt supplied with the unit (a huge 500A model which would be bombproof even without ventilation in this application) and I used the meter itself, with an internal 10A current shunt, inline both ahead and behind the controller.
" I am a bit confused in that you found the output of the panels even lower that our prior estimates but came up with higher amp hours for your estimates. We know power cannot be boosted...merely converted so how does 63 watts peak translate into that kind of amp hours."
Ah-ah, you're confusing my statements about watt-hours with amphours. As I rephrased it above--I'm using watt-hours to indicate accumulated total daily output, and using amps or amps to indicate "instant" current.
Again, that I got 63 watts instead of 100 watts is EXPECTED because I'm further north and the day wasn't perfect.
"so the positioning of the panels and the MPPT controller DO make a big difference even if my calcs are right"
Well, the MPPT does make a difference, somewhere between 4-10% acording to pretty much all the published literature which really is out there. It would have been easier to find that stuff if SolarStik mentioned it on their web site, but I'm not even sure that THEY were really aware of it.
As to aiming the panels...I didn't see a lot of difference during the noon hours, but then again, the sun was pretty high up here, I'd expect it to make a significant difference in the winter months when the sun literally is only half as high up in the sky. For someone like Kathleen, who is on the boat all day and can casually swing the panels three times a day, that's great. For someone leaving the boat, going ashore, etc. and letting it swing in the wind and current...I could see that leaving the panels horizontal (making the whole Stik a very expensive dinghy tie-up point) would be just as effective as hoping the panels didn't swing around the wrong way.
"but the argument here has always been about the CLAIMED output" Agreed. From what I've seen, and without being able to do a full load-cycle to check "real" DC... There's a quote from Arthur C. Clarke that is very appropriate here, to the effect that "Any sufficiently advanced technology is indistinguishable from magic."
The average owner will have no way to know that their "power meter" may be off by 4-5%. (Nor will it matter.) The average owner, upgrading to a Solar Stik with the supplied MPPT controller, may in fact notice a 20% increase in battery capacity. And they would simply think that was from the SolarStik, since they would have no reason to understand that the controller itself was using the raw power more efficiently (5-10%) and cycling the batteries more efficiently (10%?).
The combined effect of removing "plain" solar panels and a "plain" regulator, and replacing them with a SolarStik, could give an owner a 20% boost in the power that they were getting from "the same" panels.
Why the battery companies, and the many web sites discussing batteries, don't discuss the advantages of using pulsed DC for charging...dunno, but that word needs to get out. I tried to talk to someone at JCI about that, but of course, "the" man was on vacation.
When I take my dog for a walk, first we get in the elevator. From the dog's point of view, cables, drums, motors, switches, Mr. Otis's marvelous safety brakes, are all non-existant. The dog knows MY MASTER IS GOD, HE MAKES MAGIC. EVERY TIME THAT DOOR OPENS, THE WORLD HAS CHANGED. Dumb dog, yeah, but that's also how we typically grasp technology: It's magic. (Hey, I think of knitting the same way. Someone takes a STRING? And makes it into hats and sweaters?! That eludes me, I'm lucky enough to tie knots.)
So. I hope that explains things--a few words unfortunately dropped from the post. Some easily explained observer error from the users. Heck, why should the typical boat owner know more about pulsed-width-power systems than any one of us knows about the comparative chemistry of fiber-reinforced-composite hulls? All they should have to know, is what works.
MPPT works. Good robust wiring, works. (I might have lost some by using 8-10g wiring instead of something heavier, but I was using short runs.) And the SolarStik?
Well, if Kathleen makes it around the Horn, her SolarStik ain't gonna break off in green water. You've got to get your hands, or eyes, on one of them in person. You still may not want one on your boat--but you WILL understand the price it sells for.
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