Four Solar Panels - Parallel , Series or Series-Parallel

[Windseeker]

Originally Posted by Aussie_Sequoia

I stand by my statement and challenge anyone to place their hand over a single cell (touching the glass) and watch their voltmeter drop to nothing.
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Well, we are not conducting experiments in Outer-Space??? That would be under the Heat Transfer section of the Forum. Thanks again!

[SeaKing]

Originally Posted by Mark Johnson

A clarification about solar panel diodes... If panels have factory installed "By-pass diodes", they should not be confused with "blocking diodes", like the Schottky diodes that I put in my + wire, along with a fuse, at each panel. The By-pass diodes serve to prevent back flow within the panel, not from one panel to another. You may need to call the manufacturer to know what the function of the panel's diode really is. In my case I choose to add blocking diodes, (to panels already equipped with by-pass diodes), in spite of a small V loss, because my panels were far apart, and it is often true than one is shaded when others are not. In my application, I felt this was a good trade off.
M.

Mark,

I am about to put 12 fifty watt panels into a system, tell me more about the diodes you installed. cost , size , supplier

thanks

[McG]

Originally Posted by Aussie_Sequoia

Hello CF,

One thing I'd like to add is that unless you have an amorphous / thin-film type PV panel (such as UniSolar) then you have what is essentially a grid of cells all wired in series anyway.

Hi Aussie , so are you going to keep us in suspense regarding the amorphous panels? How does it work differently and does it impact on the way (series / parallel) you connect it

[sailingaway221]

Did anyone mention that Three or more panels are connected they should be fused?

Where three or more pannels are connected in parallel a fuse on each string will protect the conductors from damage and help minimise any safety hazards.

Also if redundancy is important the more separate systems the better...

[McG]

Originally Posted by sailingaway221

Did anyone mention that Three or more panels are connected they should be fused?

Where three or more pannels are connected in parallel a fuse on each string will protect the conductors from damage and help minimise any safety hazards.

Also if redundancy is important the more separate systems the better...

Hi Sailingaway, can you give some more info please? Like, what can happen if it is not fused and why? Are you talking of the electric wire from the panels to the Controller when you say "conductors"? Just trying to get the full pic...

[sailingaway221]

Originally Posted by sailingaway221

Rebel, I think I see what you're asking... Not how to do it but why is there a series fuse rating of 15 amps and what happens if you put two fuses instead of one.....correct?

Ok serries fuse is there to protect three or more panels. With two you are fine.

heres how that wokrs

1 shorted panel.... = no amps
2 panels 1 shorts out the other sends over 8.37 amps ( the specs on your solar panel ISC ) the other panel sends the short max of 8.37 amps.. the same as the panel was designed to handle so no worries yet.
If you install a third panel now the short gets 2 x 8.37 = 16.74 amps. This exceeds the rating on the panel and needs the 15 amp breaker for protection... so with only 2 panels you don't need a series fuse.
Heres how that works....

http://www.nmsu.edu/~tdi/pdf-resources/CC125.pdf

Now for the fuses... you ned one between the controller and the batteries.... you only need 1 for every string of solar panels inline....at the end of the positive wires between the last panel and the controller. If you put two little fuses you will be able to trouble shoot the system if there is a problem, but you will get more drop than just putting one bigger breaker for both panels.

Most MPPT controllers have a fail no flow sensor and system that acts as additional protection.... for future reference.

Hope that helps mate!

Heres the link to a previous discussion about it. Theres lots of smart people on here that know way more than I do about this...maybe ask one of them for input too?

http://www.cruisersforum.com/forums/...ing-48230.html

[hellosailor]

http://www.nmsu.edu/~tdi/pdf-resources/CC125.pdf

Seems to apply very specifically to solar panels that are connected to utility power systems, i.e. "mains voltage" as in residential and commercial land systems. In those systems, if the connecting device fails then the solar panels are potentially exposed to full mains voltage, which could fry them.

In that situation a fuse would protect the panels (and their wiring) in the event that the connecting device failed. That's not intended to protect anything from a failure in the panels though.

Using a serial-panels-fuse in a boat is something entirely different. You'd be trying to protect the panels from an unlikely situation where the output from the entire panel "string" was dead shorted to itself. If there was a need to do that, you'd need to fuse the string "for" the maximum amperage from one panel, since the series configuration raises voltage--but not amperage. Assuming there was a real need to fuse them that way.

But the pdf is concerned with having a utility company connected to the panels, not at all a marine installation, unless you've got them exposed to your dockside power somehow.

[sailingaway221]

Maybe ask someone that knows for certain... but as far as I know if you have more than two in parallel you need a series fuse no matter where you put them....I put the reference more to show why you need it than for an example on a boat... but it is the same theory. Heres another link to another forum... if they let me post it but here they say the same.. 2 or less you're fine 3 or more protect it.

http://www.wind-sun.com/ForumVB/show...se+solar+panel

[Thumbs Up]

Here is our dilemma: We have two 190 watt panels on our catamaran. They are on opposite sloping sides of the cabintop. The panels don't seem to have any internal diodes as they are badly effected by any shading whatsoever. Currently they are hooked up in series with 10awg wire through an Outback mppt to a 400 amp/hour battery bank and we are averaging only 120 a/h a day and reach full charge only on very sunny days. When any portion of a panel is shaded the output is drastically reduced. Should we 1. Keep them in series but add a bypass diode across each panel connection. We'd be taking better advantage of mppt and the high voltage would be less current drop through our #10 wire but we might get a loss due to the diodes themselves or 2. Do we connect them in parallel and not get any loss from the partially shaded panel (usually one panel has some shade most of the time).
I am also interested in what anyone has to say about the uni-solar or other brands of amorphous panels. I was all set to use those but they stopped making the 4.5' by 15" and now the shortest ones are 9' and make only 63 watts but are guaranteed to produce their rated wattage. Now there are a few companies gearing up to make these flexible amorphous panels in the U.S. but that is all I know about it and would like more info. Thanks everyone, Phil

[noelex 77]

Originally Posted by Thumbs Up

Here is our dilemma: We have two 190 watt panels on our catamaran. They are on opposite sloping sides of the cabintop. The panels don't seem to have any internal diodes as they are badly effected by any shading whatsoever. Currently they are hooked up in series with 10awg wire through an Outback mppt to a 400 amp/hour battery bank and we are averaging only 120 a/h a day and reach full charge only on very sunny days. When any portion of a panel is shaded the output is drastically reduced. Should we 1. Keep them in series but add a bypass diode across each panel connection. We'd be taking better advantage of mppt and the high voltage would be less current drop through our #10 wire but we might get a loss due to the diodes themselves or 2. Do we connect them in parallel and not get any loss from the partially shaded panel (usually one panel has some shade most of the time).
I am also interested in what anyone has to say about the uni-solar or other brands of amorphous panels. I was all set to use those but they stopped making the 4.5' by 15" and now the shortest ones are 9' and make only 63 watts but are guaranteed to produce their rated wattage. Now there are a few companies gearing up to make these flexible amorphous panels in the U.S. but that is all I know about it and would like more info. Thanks everyone, Phil

I think you will do better with the panels wired in parallel.
Why not string some wire on a temporary basis and let us know the results ?
120Ahrs from 380W is not great, but shade is always going to have an effect (although less when wired in parallel). What is your location?

[noelex 77]

Originally Posted by Thumbs Up

.
I am also interested in what anyone has to say about the uni-solar or other brands of amorphous panels. I was all set to use those but they stopped making the 4.5' by 15" and now the shortest ones are 9' and make only 63 watts but are guaranteed to produce their rated wattage. Now there are a few companies gearing up to make these flexible amorphous panels in the U.S. but that is all I know about it and would like more info. Thanks everyone, Phil

Amorphous solar panels are more shade tolerant, but are much larger and more expensive. Their main advantage is they are light and flexible which means they can be used where rigid panels cannot. If you have the room to permanently mount rigid panels these are always going to be a better option. Rigid panels will give you more AHrs per $, or AHrs per surface area, even in a location on the boat that gets some shading.

[sailingaway221]

Phil, I have 2 170 watt panels wired up to individual controllers and I have 660 amp hr bank... by 11am each day mine have fully recharged almost anything I have used out of the batteries. ... I have way more power than I need ...... Try running the as two individual units...

[McG]

Originally Posted by sailingaway221

Phil, I have 2 170 watt panels wired up to individual controllers and I have 660 amp hr bank... by 11am each day mine have fully recharged almost anything I have used out of the batteries. ... I have way more power than I need ...... Try running the as two individual units...

If I may, how does the battery bank accept different voltage/current imputs from 2 controllers simultaneously? I guess that in your scenario, the inputs will be very similar, yet not exactly the same. If one controller sends less volts than the other one, what happens in realtime? Does the battery benefit from both charges?

[noelex 77]

Originally Posted by McG

If I may, how does the battery bank accept different voltage/current imputs from 2 controllers simultaneously? I guess that in your scenario, the inputs will be very similar, yet not exactly the same. If one controller sends less volts than the other one, what happens in realtime? Does the battery benefit from both charges?

A single MPPT regulator with multiple panels does not work efficiently unless the panels are experiencing the same conditions. On a boat this is often not the case with some shadowing of one panel while others are in full sun.
A MPPT regulator for each panel enables the regulator to determine the optimum input voltage for each solar panel. The output voltage will be the same because they are connected to same battery bank.
A dual system also provides redundancy, but it costs more and the more basic, lower current, MPPT regulators often do a poor job of tracking the correct power point and have simple battery charging points which reduces battery life considerably.

[sailingaway221]

McG, I had the work done by a friend who has been working on boats electrical systems forever. I'm not on the boat to look, but from memory the panels go to individual controller for each one , then through a Xantrex Pathmaker a breaker and to the batteries. When I get back I'll see if I can see how they go from the Xantrex to the batteries, but I believe the panels are combined as they come out of the Xantrex as there is only one breaker between that and the batteries. In real time either or both panels can charge the batteries and if one panel is covered the other still provides max output.