Best solar panels for the buck

[Sumner]

Interesting data, thanks for posting it.

I'm interested in what you are doing for 'fusing'. In parallel you can put a small fuse on each panel so that if it shorts internally the amperage from the other panels can't go to it as that will blow the fuse.

In series you can't use the small fuses since all of the amps would blow them if in series. If you just use one large fuse on the circuit then what happens if a panel shorts internally? Is there a chance that it will burn.

I'm going to stay parallel for sure and hope that we are 'over paneled' most of the time and run the boats diesel or the Honda generator for the few times we need more,

Sum

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[prroots]

Interesting data, thanks for posting it.

I'm interested in what you are doing for 'fusing'. In parallel you can put a small fuse on each panel so that if it shorts internally the amperage from the other panels can't go to it as that will blow the fuse.

In series you can't use the small fuses since all of the amps would blow them if in series. If you just use one large fuse on the circuit then what happens if a panel shorts internally? Is there a chance that it will burn.

I have an AWG 10 duplex wire running from underside of panels to controller. A 40 Amp fuse is installed on the positive conductor a few inches before it enters the controller. Actually if I end up with series I could switch to a 10 Amp fuse and if parallel to a 20 Amp fuse. I guess you could say that my fuse protects the wire not the panels.
Pete

 

[prroots]

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

 

[prroots]

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.
Pete

 

[prroots]

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

 

[prroots]

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

 

[sea_casper]

All are in series

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

All the cells must be in series, since the open circuit voltage of the panel is listed as 33 volts. and a single cell can only produce 0.6 volts. It would seem that only a single blocking diode is required.

However,
"[FONT=arial, sans-serif][SIZE=-1]Blocking diodes placed at the head of separate series wired strings in high voltage systems can perform yet another function during daylight conditions. If one string be comes severely shaded, or if there is a short circuit in one of the modules, the blocking diode prevents the other strings from loosing current backwards down the shaded or damaged string. The shaded or damaged string is “isolated” from the others, and more current is sent on to the load. In this configuration, the blocking diodes are sometimes called “isolation diodes”."[/SIZE][/FONT]

 

[prroots]

All the cells must be in series, since the open circuit voltage of the panel is listed as 33 volts. and a single cell can only produce 0.6 volts. It would seem that only a single blocking diode is required.

However,
"[FONT=arial, sans-serif][SIZE=-1]Blocking diodes placed at the head of separate series wired strings in high voltage systems can perform yet another function during daylight conditions. If one string be comes severely shaded, or if there is a short circuit in one of the modules, the blocking diode prevents the other strings from loosing current backwards down the shaded or damaged string. The shaded or damaged string is “isolated” from the others, and more current is sent on to the load. In this configuration, the blocking diodes are sometimes called “isolation diodes”."[/SIZE][/FONT]

Thanks. I don't really understand your post. I realize that all the cells must be placed in series. My question related to where the connections were in the attached schematic. Also, it is my belief that all diodes shown are the bypass type. Three of the 4 diodes bypass each of 3 strings. The 4th seems to bypass two of the 3 strings. I'm not sure where blocking diodes come into play as it relates to the schematic?
Pete

 

[sea_casper]

What Schematic?

Thanks. I don't really understand your post. I realize that all the cells must be placed in series. My question related to where the connections were in the attached schematic. Also, it is my belief that all diodes shown are the bypass type. Three of the 4 diodes bypass each of 3 strings. The 4th seems to bypass two of the 3 strings. I'm not sure where blocking diodes come into play as it relates to the schematic?
Pete

What schematic?

 

[Ron McCoy]

I like the Kyocera 130 (older model) or 135 (newer model) watt panels. Kyocera has one of the few warranties that cover their use in a marine environment. Ours are about six years old and look like they're new. They're installed over the bimini, out of the way of the boom and other obstructions. Either the Xantrex or BlueSeas controllers will work fine - it's a matter of your pocket book and electrical needs.

 

[prroots]

What schematic?

Also you cannot bypass a string of cells with a diode.

Check post 126
Pete

 

[sea_casper]

I missed the pdf.

Anyway, the top 3 diodes each bypass 2 columns of cells, the fourth diode redundantly bypasses 4 columns of diodes.

If a cell is shaded it appears as a resistor rather than voltage generator. A current passing through it results in a voltage which subtracts from the generated voltages of the unshaded cells, in the same way any resistance inserted in series with the panel would.

The diode will thus bypass a cell or series of cells if their net voltage is less than .5 volts, providing a low impedance current path for the rest of the array. If the group of cells are generating more than a net of zero volts the diode is reverse biased.

The 4th diode only reduces the voltage loss to .5 vollts if the left most 4 columns are shaded.
A 5th diode would do the same if the right 4 columns were shaded.

None of the diodes function as a "blocking diode" which is still needed for each panel' for two panels in parallel, one is needed for 2 panels in series.

Remember 1 ohm of resistance results in a loss of 4 volts @ when 4 amps is being generated.

I hope that explains it better than my quote from a manufacturer's site.

I retracted my statement on a single diode not being able to bypass more than 1 cell, I don't know what I was thinking about.

 

[prroots]

I think I've come up with a test method that might allow me to more accurately compare series and parallel modes of operation. At intervals of approximately 30 minutes I switch back and forth between parallel and series. On these occasions, I record the collected Ah (one of the variables output by my controller) and time of reading. I then calculate average Amps during the interval by dividing the Ah accumulated over the interval by time in hours. This method will smooth out the erratic changes in output caused by cloud cover. Hopefully, the effects of cloud coverage and effect of boat orientation on shading will average out between series and parallel over the course of a day to make the comparison meaningful. I have attached a spreadsheet showing the results for an afternoon with heavy shading. The results are calculated in two different ways, but it does show that parallel outperforms series by at least 40% under the conditions encountered.

As an aside, I've discovered that when the wind comes from the prevailing direction just South of East, I get significant shading most of the day on the port side panel from the wind generator and its mast. What makes it particularly nasty is that the shading cuts across all 3 substrings. Despite that, I do not believe that any substring is being bypassed. I base that opinion on the fact that the array Voltage is 50-55 Volts while in series mode (see the attached graph). This suggests that both panels are contributing to the output. I wonder if the loss in solar power is compensated by the output from wind generator? I think not, however, the wind generator does create output on occasions when there is no solar to speak of. Knowing what I know now, I'm not sure if I would have installed the wind generator?
Pete

 

[Ron20324]

... This suggests that both panels are contributing to the output. ...Pete

Interesting, for sure. I have wondered which was best, series/parallel. I wonder if you can look at one other situation. I did series wiring. I wonder if, as the sun goes down, can you see when either wiring means would have the array voltage become so low as to not be above battery (and thus charge) voltage. It seems series, doubling the voltage, would allow charging later into the sunset, and earlier at sunrise.

It would seems that per your post 133, favoring parallel wiring, that switching between the two might provide more "per-daylight hours" charging? Might be best to watch the battery monitor for charge input when switching between s/p.

 

[prroots]

Interesting, for sure. I have wondered which was best, series/parallel. I wonder if you can look at one other situation. I did series wiring. I wonder if, as the sun goes down, can you see when either wiring means would have the array voltage become so low as to not be above battery (and thus charge) voltage. It seems series, doubling the voltage, would allow charging later into the sunset, and earlier at sunrise.

It would seems that per your post 133, favoring parallel wiring, that switching between the two might provide more "per-daylight hours" charging?

Thanks. I will look into that, but you might not appreciate that my panels are nominal 18 Volts (with Vmp of about 26 Volts) so even in parallel mode I have more overhead than nominal 12 Volts panels. Theefore, the effect you speak of might not be as pronounced as with nominal 12 Volt panels
Pete

 

[Sumner]

Just thought I would throw this out there.....I was talking to a tech at Blue Sky yesterday about our MPPT controller and asked him about serial vs. parallel and shading and blocking diodes.

Unlike Pete we have 12 volt panels that operate a little over 17 volts not the higher voltage that Pete's panels operate at. For our situation he recommended that we stay parallel with the panels and said to not worry about other blocking diodes between panels considering that at times one panel might get shaded since even in the shade the panel will go up to the 17 volts or near to it. It just won't produce much amperage. Since it is up at 17 volts the other panels won't back-feed into it and as it gets better sun it will contribute more.

Personally I like the parallel as if one panel is damaged, as happened to us, it is just a matter of disconnecting it. I'm not interested in going back and forth during the day to achive a small amount of additional charge as I think I would soon tire of that.

Likewise trying to re-orientate the panels during the day. We just tried to 'over-panel' with the Endeavour since we had room for more panels. 180 watts was taking care of over 90% of our needs (we have a frig) on the Mac so 480 on the Endeavour should hopefully take care of 99% of our needs as we hope to operate in a similar mode with just a little bit larger frig/freezer.

On the Mac...

...I did change the way the panels are mounted to get them more inboard and also made the 40 watt panel mount in such a what that I can tilt it fore-aft some. I did that mainly so that at home it is facing south where we park the trailer and will keep the batteries up during the winter and will shed the snow a little better. On the water I'll bet we leave it horizontal most of the time,

Sum

[FONT=Arial, sans-serif]Our Endeavour 37[/FONT]
[FONT=Arial, sans-serif]Our Trips to Utah, Idaho, Canada, Florida[/FONT]
[FONT=Arial, sans-serif]Our MacGregor S Pages[/FONT]
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[prroots]

We're now cruising the Bahamas. Have not had to run engine once on account of batteries. In fact we've been using inverter liberally to run microwave, air popper, power tools, etc Of course, we also have a wind generator which does complement the solar on cloudy days. We left it in parallel mode with panels horizontal since our departure from Florida on March 2nd. Just haven't had time to do any testing since then.
Pete

 

[Sumner]

We're now cruising the Bahamas. Have not had to run engine once on account of batteries. In fact we've been using inverter liberally to run microwave, air popper, power tools, etc Of course, we also have a wind generator which does complement the solar on cloudy days. We left it in parallel mode with panels horizontal since our departure from Florida on March 2nd. Just haven't had time to do any testing since then.
Pete

Sounds like you achieved success . It sure is nice not having to listen to anything run once or twice a day in order to store some electrons . Wish we were over there anchored nearby,

Sum

[FONT=Arial, sans-serif]Our Endeavour 37 [/FONT] [FONT=Arial, sans-serif]
Our Trips to Utah, Idaho, Canada, Florida[/FONT] [FONT=Arial, sans-serif]
Our MacGregor S Pages[/FONT] [FONT=Arial, sans-serif]
Mac-Venture Links[/FONT]

 

[prroots]

We've accumulated a few weeks of usage in the horizontal/parallel configuration. The daily output has ranged from 140 to 200 Ah. The average is 152. We are able to run our inverter with microwave, vacuum, air popper, etc without limitations. It's been great. Of course, switching all cabin and anchor lights to LED has certainly helped. Since we are now cruising in the Bahamas we haven't had time to do more testing, but will get back to it when the opportunity presents itself.
Pete

 

[prroots]

We're getting ready to put the boat on the hard for the hurricane season. What to do with the panels? We'll leave them in place, but should we cover them to prevent collection or simply disconnect them from MPPT controller and let them sit at Voc? We're afraid to leave them in operation without any load whatsoever for fear of overcharging our 4 golf cart batteries.
Pete