Series Or Parallel solar panel?

[Bruce K]

I am about to install 2 new Sharp 188w PV panels. Open circuit voltage 29.6V my 30a MPPT controller max ocV is 65V, so that is Ok. I think I will connect the panels in series to minimise cable loss. Panels are mounted flat on roof so should never be 100% output. Panels may occasionally have a small amount of shadowing. Any thoughts from those who know? Regards BK

[Reefmagnet]

12 VDC?? Parallel is the way it's normally done. I think a shaded series panel will affect all other series panel's output.

[Bruce K]

12v DC, but regulator is Mppt so input voltage can be up to 65v.

[nigel1]

There have been a few threads on this subject, which should help you decide (or confuse you )
http://www.cruisersforum.com/forums/...lel-68096.html

http://www.cruisersforum.com/forums/...lel-59513.html

[noelex 77]

There has been a lot of debate about series vs parallel connections. The performance when part of the array is in shadow is the important difference.

Unfortunately, there does not seem to be a definitive answer, as there is data and user experience that support both types of connections. The performance can be mathematically predicted, but there are so many shadow permutations and the maths becomes too difficult for a realistic model, at least for me.

My reading of the various pieces of evidence is that parallel just wins and this is how I have wired my panels, but there is still some doubt in my mind.

If you are going with parallel make sure there is room to install suitably sized cable. Parallel connection needs a very hefty wire size for this sized array, and sometimes this will just not physically fit. This can swing the balance in favour of series, where the wire size only needs to be about 1/2 the overall area.

One factor that influences the panels' performance under series connection, is how many bypass diodes has been internally fitted. This varies from zero (which is very bad for panel longevity) to 8 or more. The specifications for your panel are here (I think this is the correct panel):
http://www.sharp.net.au/cms/products...20Brochure.pdf

Sharp don't list the number of bypass diodes that have been internally fitted. Often this means the panel does not have many, which would push me further into recommending a parallel connection.

If you do want to use a series connection, it worthwhile installing an additional bypass diode around each panel.

Just a word of warning . You mention the manufacturer has specified a maximum Voc of 65v. In this case the combined Voc of your panels is 59.2v so it is fine. However, many manufacturers specify a maximum input voltage. It is often assumed this must be the Voc of the panels, but this is not the case.

Voc is maximium voltage produced (with no current flowing) under the test conditions. Solar panels can produce a higher voltage than this in some instances.

It is very important never to exceed the maximium voltage rating of solar controller. If you exceed the maximium current rating most solar controllers will self protect and no damage will be done, but even a brief over voltage situation will often instantly damage the controller. For this reason most manufacturers recomend that you choose an array Voc well below the maximum voltage input specification.


Edit: I note in this later post you state the maximum input voltage is 65v (not Voc as in your first post)

Originally Posted by Bruce K

12v DC, but regulator is Mppt so input voltage can be up to 65v.

As I mentioned above this is not the same as Voc. You should check exactly what the specifications say. If the max input voltage is 65v the controller may not suitable for series connection of your panels. At the very least I would double check with the controller manufacturer because you will be very close to the limit. If you get this wrong the controller will be damaged.

[sailorboy1]

From my reading I think it really matters more what the Vmp of the panels are. If they are large panels you already probably have a MPPT controller, which is going to adjust for the shading. The biggest shading power loss far as real use goes is if you have a 12V panel supplying a 12V system, which means any shade pretty much wipes out the output.

So for for a multi 12V panel system it is better to install in series and use a MPPT controller. For larger voltage panels that you already have a MPPT controller I don't feel it really matters except as a paper writing exercise.

And this is my opinion so if you want to throw a spear at me don't waste a good sharp one

[imjack]

why would it wipe out output. new at this so please forgive any questions which seem off the mark(+)

[nimblemotors]

Originally Posted by imjack

why would it wipe out output. new at this so please forgive any questions which seem off the mark(+)

Solar Panels and MPPT

[Stu Jackson]

Originally Posted by noelex 77

There has been a lot of debate about series vs parallel connections. The performance when part of the array is in shadow is the important difference.

noelex is right.

The best answer I heard just the other day on another boating forum: wire it so you can easily switch between the two with multiple panels and see what works for you.

For example, we get mostly west winds here during the summer months from April to September. That dictates shade after noon at anchor.

If your boat is in a marina and you're using the panels instead of shorepower, your direction will dictate what works based on the shading you get.

Not so hard.

Like all things boating, it depends.

Give yourself the flexibility.

[newhaul]

Personally I would go parallel with those panels you have the mppt controller for it and there would be little additional benefit for charging 12v bank in series.

[travellerw]

I'll throw out another option. Buy a second cheap mppt and wire the separately. Its the best option in terms of shading, and redundancy.

Sent from my Nexus 4 using Cruisers Sailing Forum mobile app

[catman]

Each solar panel should have its own controller. Each solar panel will be wired with an appropriate, water sealed, cable to a controller( mounted inside ).
The output of the controllers can then be wired in parallel to a battery bank with a minimum #10 awg wire. The way the systems are designed will not allow for the connection of series solar panels. Each controller shall have a dedicated cable that is designed for resistance and length for that particular controller connecting it to the solar panel. Whether solar panels are connected in series or parallel is determined by the load. If you have a 12volt battery as a load the panels have to be connected, after the controller, in parallel.
Cheers, Catman

[newhaul]

Why does everyone want to make something simple complex wire the 2 panels in parallel both + to the + input on the controller and both - to the - on the controller done and done just remember to wire from load to source ( batteries to the controller then the panels to the controller.) KISS keep it simple

[catman]

To KISS or not.
Unfortunately if you connect a shaded solar panel to a non shaded solar panel in parallel the parallel connected panels will give an averaged output which will be less than 12 volt. If each panel has its own controller the controller output will never be lower than the load (internal diodes) which means only the solar panel,that is in the sun will charge your batteries.
Cheers, Catman

[noelex 77]

Originally Posted by catman

Each solar panel should have its own controller.

This is an option, but is not common. There is no point with non MPPT controllers. With an MPPT controller the potential tracking is better with multiple units, but the accumulated self consumption can erode any potential gain and the cost is high, especially with good quality controllers.

Originally Posted by catman

The output of the controllers can then be wired in parallel to a battery bank with a minimum #10 awg wire.

The wire size depends on the current and the distance. It is easily calculated.

Originally Posted by catman

The way the systems are designed will not allow for the connection of series solar panels.

With an MPPT controller series connection is fine providing you do not exceed the maximum input voltage of the controllers. In the larger controllers this is 150v or more, so multiple panels in series are possible without exceeding the specifications.

The debate is centred around the question if this series connection is more, or less efficient than parallel.

Originally Posted by catman

Each controller shall have a dedicated cable that is designed for resistance and length for that particular controller connecting it to the solar panel.

The lower the resistance the better, in terms of performance.

Originally Posted by catman

Whether solar panels are connected in series or parallel is determined by the load. If you have a 12volt battery as a load the panels have to be connected, after the controller, in parallel.

The panels are connected to the controller which is then connected to batteries. With a non MPPT controller the nominal panel voltage should match the battery voltage and the panels need to be connected in parallel. For a MPPT controller the panel/array voltage can be higher than the battery voltage. Both series and parallel are generally possible. A very small number of MPPT controllers will boost panel voltage, but this is rare.