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Old 10-02-2012, 18:41   #91
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re: Best Solar Panels For The Buck

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Originally Posted by hellosailor View Post
Pete, you might want to ask the mppt maker, or check their manual to see if it mentions efficiency versus voltage. Sometimes the controller itself may be a couple of percent more efficient at a hgher voltage, sometimes not. Of course if you've got long wire runs, putting them in series will also help to counter the voltage drop from the extra wire length.
Thanks. The manual includes efficiency curves for different voltages
Pete
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Old 10-02-2012, 18:50   #92
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re: Best Solar Panels For The Buck

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prroots,

Do you have pictures of the panels flat.
In the picture I see solid forward bars, so I do not see how to tilt the panels.

Most people are using telescoping bars to make the tilt adjustment.
Thanks. We went simple and strong. We have 3 sets of fixed poles for tilt forward, horizontal, and tilt back. We did consider telescoping but could not figure out how to get the 30" of travel.
Pete
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Old 11-02-2012, 09:33   #93
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re: Best Solar Panels For The Buck

After redoing my wiring to make it easy to switch back and forth between parallel and series we finally have a clear sky for awhile. Here is a graph showing the power in both conditions. The lowest curve is array voltage which shows whether we're in series or parallel mode. One anomaly is that input power is lower than output power while in parallel mode; I'm guessing that this must be due to errors in the shunt resistors.We see that the spread between input and output power increases while in series mode which verifies that controller efficiency decreases with higher Voltage. Of course, we also have greater line loss while in parallel mode. Since the output power is what matters, we see hardly any difference between the two configurations. Note: there was no shading at the time on either panel.
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Old 11-02-2012, 09:57   #94
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re: Best Solar Panels For The Buck

That is why most are using 10 gage or bigger wiring and the shortest possible wire runs
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Old 11-02-2012, 10:04   #95
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re: Best Solar Panels For The Buck

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That is why most are using 10 gage or bigger wiring and the shortest possible wire runs
Thanks. We're running AWG 8 cable. Since the output power seems to be unchanged in either mode, the conclusion I draw is that the loss of controller efficiency at higher voltages associated with series mode is almost exactly offset by the increased line loss in parallel mode. Our controller is providing all the results you see The boat is oriented so there is no shading on either panel. Once I complete these tests I will be investigating the effects on shading. That could get interesting; stay tuned
Pete
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Old 15-02-2012, 15:17   #96
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re: Best Solar Panels For The Buck

As an update on my Morningside TriStar MPPT 45 controller, I have some good news and some not so good news. The USB-to-serial adapters that I have used elsewhere with good luck, doesn't work reliably with the controller's RS-232 interface. I finally purchased and received today the one Morningside recommends, the Trendnet model TU-S9. That one works fine. Unfortunately none of their literature recommends it or any other for that matter. For those considering this controller and wishing to interface their laptop to it, I suggest they figure on purchasing the recommended adapter. The good news is that their recommended adapter works fine; the bad news is that I wasted a lot of time diagnosing and troubleshooting the one I already use. They could save themselves and their customers a lot of wasted effort by documenting a list of successfully tested USB-to-serial adapters.
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Old 16-02-2012, 10:44   #97
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re: Best Solar Panels For The Buck

As a further update on my Morningside TriStar MPPT 45, I learned that the Power Input variable is very inaccurate due to the way it's measured. They provide it primarily for engineering use, not customer use. Guess I'll ignore it from now on. Also, they told me that the probable reason my original USB-to-serial adapter didn't work was due to voltages lower than specified for RS-232.
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Old 16-02-2012, 10:59   #98
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re: Best Solar Panels For The Buck

"Also, they told me that the probable reason my original USB-to-serial adapter didn't work was due to voltages lower than specified for RS-232."
Ignore the man behind the curtain?

IIRC RS-232 is supposed to be running at twelve volts, but a lot of computers (Dell is infamous) run the ports at 5 volts, and some equipment craps out at that point. HOWEVER, the vast majority of equipment is just fine with it.

A bigger issue is simply non-compliant hardware and software. Microsoft keeps what is called a "Hardware Compatibility List" aka "HCL" and vendors have the option of paying a steep price (like a UL or CE approval fee) to have their equipment run through a gamut of tests, or not. If they pay and pass, they get to use the Windows logo for the one OS they've tested for, and you stand a very good chance that the stuff will work for you as well.
Obviously the stuff from a Chinese basement clone shop is not going to invest that money--and some better known brands don't either. But the stuff like USB/serial adapters that IS on the HCL, that does earn the logo, often works when the uncertified stuff just doesn't. Might cost an extra $5, often less.

When USB had been out for something like 5? years? and XP was still the latest MS OS, there were all of two vendors and three products on the HCL for USB-to-serial. There are more now.<G>
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Old 20-02-2012, 03:51   #99
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re: Best Solar Panels For The Buck

I'm a bit frustrated in my testing on the effects of shading. When one switches back and forth between series and parallel mode, the effect is totally masked by the effects of the weather ie, clouds passing in front of sun. The effects of weather cause the power to fluctuate wildly making it next to impossible to reliably detect the effects of shading in parallel vs series mode. I really need to be patient and wait for a cloudless day to conduct the experiments.
Pete
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Old 21-02-2012, 05:19   #100
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re: Best Solar Panels For The Buck

I requested and received the schematic of my Photowatt PW2050-210 panels in order to understand the placement of bypass diodes. Each panel consists of 54 cells arranged in 6 columns of 9 cells. I can't understand the schematic. It appears that the 1st and 2nd columns are connected in series as are the 3rd and 4th as well as the 5th and 6th. That makes 3 strings of 18 cells. I'm wondering if these 3 strings are placed in series within the junction box because I can't find the connection on the schematic. Also, there are 4 diodes, but they do not appear to simply bypass the 3 strings of 18 cells which would require only 3 diodes. Can anyone figure it out?
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Old 21-02-2012, 06:04   #101
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re: Best Solar Panels For The Buck

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I requested and received the schematic of my Photowatt PW2050-210 panels in order to understand the placement of bypass diodes. Each panel consists of 54 cells arranged in 6 columns of 9 cells. I can't understand the schematic. It appears that the 1st and 2nd columns are connected in series as are the 3rd and 4th as well as the 5th and 6th. That makes 3 strings of 18 cells. I'm wondering if these 3 strings are placed in series within the junction box because I can't find the connection on the schematic. Also, there are 4 diodes, but they do not appear to simply bypass the 3 strings of 18 cells which would require only 3 diodes. Can anyone figure it out?
Pete
Nice panels. The series connections are in there, right where the connections to the diodes tap into it. They are probably part of the construction, although I wonder why they didn't do the same at the other side...

The extra diode is to make sure that there are never more than 2 diodes in series for a fully shaded panel. See how it parallels two other diodes that are in series?

ciao!
Nick.
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Old 21-02-2012, 06:16   #102
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re: Best Solar Panels For The Buck

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Nice panels. The series connections are in there, right where the connections to the diodes tap into it. They are probably part of the construction, although I wonder why they didn't do the same at the other side...

The extra diode is to make sure that there are never more than 2 diodes in series for a fully shaded panel. See how it parallels two other diodes that are in series?

ciao!
Nick.
Thanks; you must be right, but I still can't make out the series connections on top. Yes, each of the 3 strings of 18 cells is protected with a bypass diode and then the 4th diode protects the combination of 1st and 2nsd strings. As you say, it limits the maximum number of diodes in series to two.
Pete
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Old 21-02-2012, 06:42   #103
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re: Best Solar Panels For The Buck

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Originally Posted by prroots View Post
As an update on my Morningside TriStar MPPT 45 controller, I have some good news and some not so good news. The USB-to-serial adapters that I have used elsewhere with good luck, doesn't work reliably with the controller's RS-232 interface. I finally purchased and received today the one Morningside recommends, the Trendnet model TU-S9. That one works fine. Unfortunately none of their literature recommends it or any other for that matter. For those considering this controller and wishing to interface their laptop to it, I suggest they figure on purchasing the recommended adapter. The good news is that their recommended adapter works fine; the bad news is that I wasted a lot of time diagnosing and troubleshooting the one I already use. They could save themselves and their customers a lot of wasted effort by documenting a list of successfully tested USB-to-serial adapters.
Pete
Yep, welcome to the digital age! Had the same thing trying to download RS-232 data from my Paktraker battery monitor. Should be simple right? Not always:

First I bought a USB to COM cable to connect to the Paktrakr.
But, Microsoft no longer includes Hyperterminal com program with software
Had to download trial Hyperterminal program into computer
Could not get it to work.
Found out that not all USB to Com cables work with MS Vista.
Bought new VISTA compatable cable. Trial Hyperterminal trial program expired. Still could not get it to work.

Solution: I dusted off an old Windows 98 Laptop bought it to the boat connected old com cable and it worked the first time.

Sometimes you need to go backwards to go forward!
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Old 21-02-2012, 07:18   #104
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re: Best Solar Panels For The Buck

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Yep, welcome to the digital age! Had the same thing trying to download RS-232 data from my Paktraker battery monitor. Should be simple right? Not always:

First I bought a USB to COM cable to connect to the Paktrakr.
But, Microsoft no longer includes Hyperterminal com program with software
Had to download trial Hyperterminal program into computer
Could not get it to work.
Found out that not all USB to Com cables work with MS Vista.
Bought new VISTA compatable cable. Trial Hyperterminal trial program expired. Still could not get it to work.

Solution: I dusted off an old Windows 98 Laptop bought it to the boat connected old com cable and it worked the first time.

Sometimes you need to go backwards to go forward!
Wow, back to Windows 98; that was pretty extreme Have you contacted the manufacturer for recommended USB-to-serial converters?
Pete
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Old 21-02-2012, 07:27   #105
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re: Best Solar Panels For The Buck

or...... you give in and buy a Mac

ciao!
Nick.
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