Solar Panels - Series or Parallel ?

[Cotemar]

Originally Posted by s/v Jedi

If you end up with 2 panels far apart and you get a positive and negative wire from each panel together at the controller, you can easily choose either series or parallel connection. The loss in the cabling will be exactly the same for either method because the wire is the same length and diameter and the same current flows through it. This means that on a boat, the series connection still outperforms the parallel connection in that case. You will find it is very hard to find a case for parallel connection on a boat, except when the controller does not support it.

ciao!
Nick.

I am thinking this thread has a Nicks Law and everyone else has to run with Ohm's Law. Why would anyone go and wire two panels that are far apart in parallel then at to MPPT controller connect the wires in series and penalize themselves with the series shading issue? Nick has his reality distortion.
Don’t believe everything you think.

[s/v Jedi]

Originally Posted by stevensuf

that is what i did, took 2 panels connected in parallel to the mppt controller, measured current/voltage then shaded half of one with a towel, battery was pretty dead, then did parallel comparison, much more output in parallel with one half shaded and the panels have 3 bypass diodes . try it yourself its easy to do.

as others have said if your panels are never shaded, series is better, but if partial shading then parallel is better.

It is completely the other way around. Read the tests done earlier in the thread. When you shade half a panel in your setup, output drops to 50%, ie you lose the whole panel. In series, you only lose the section(s) that got shaded, the others keep delivering power.

cheers,
Nick.

[CFR]

Hi all, one question from my side. Sorry i am mechanical and not electrical engineer. I just considering to install one big panel at my radar arch and was looking to sunpower e20 with 96 cells and 330 Wp. Total Voltage is rated at 54 V with 3 bypass diodes. Am i right that i should try to change the wiring at the terminal box to divide in 3 independent string each with max 18 V and 32 cells to minimize problem by shade from my antenna and windgen ? or does the doides doing exactly that already. sorry little bit confused

[s/v Jedi]

Originally Posted by Cotemar

I am thinking this thread has a Nicks Law and everyone else has to run with Ohm's Law. Why would anyone go and wire two panels that are far apart in parallel then at to MPPT controller connect the wires in series and penalize themselves with the series shading issue? Nick has his reality distortion.
Don’t believe everything you think.

Cotemar, you are the one distorting reality. Open your mind to scientific method, read what has been written about tests by others than me in this thread, and you will find that you are wrong and that it is parallel connection that gets the penalty and series connection outperforms in shading. The proof is in this thread, delivered by others. Don't just repeat what others have told you once... they were wrong.

Now about Ohm's law and the wiring part: do the math and find that I am correct, like explained by someone else too. Even though it looks weird to you to wire in series with the two panels that far apart, it is factually 100% equal in cable loss vs the parallel connection. Follow Ohm's law and you will arrive where I am waiting for you

ciao!
Nick.

[s/v Jedi]

Originally Posted by CFR

Hi all, one question from my side. Sorry i am mechanical and not electrical engineer. I just considering to install one big panel at my radar arch and was looking to sunpower e20 with 96 cells and 330 Wp. Total Voltage is rated at 54 V with 3 bypass diodes. Am i right that i should try to change the wiring at the terminal box to divide in 3 independent string each with max 18 V and 32 cells to minimize problem by shade from my antenna and windgen ? or does the doides doing exactly that already. sorry little bit confused

Ignore the naysayers, the manufacturer of your panel knows exactly what they did by wiring the sections in series. Do not modify it and wire the 54V output to your MPPT controller that is rated for that voltage, and you have maximum performance in shading and non shading. The output during shading will be an avg. of 25% better than when you modify for parallel connection.

Some day all panels will be like yours and the myths about series supposedly being bad for partial shading will be put to rest.

ciao!
Nick.

[Cotemar]

CFR,

SunPower (e20) 327 watt is a sweet panel.
61" x 41" inch and at 41 lbs this is the smallest and lightest solar panel you can buy putting out 327 watts.

You do not have to alter anything. They work great as designed.

[CFR]

to Cotemar, yes thats why i consider to use it. a space is allways a problem why not using the best one can you get although i have to see if it isnt too big and bulky

[prroots]

Today we oriented the boat so that the stern faced North which causes shading by wind generator and radar radome. The day was partly cloudy which really confused the results as clouds passed in front of the sun. In the graph you an see when it's in parallel or series by looking at the array voltage. Also the transitions are indicated by the power dropping to zero. Can anyone make sense of it?
Pete

[Cotemar]

prroots,

It’s all fun stuff. These graph are impressive, but in the end you are
REALLY OVER THINKING THIS.

Here is your system shown in these two pictures.

Here are the two rules most are following:
Use parallel wiring if your panels are in two locations, far apart.
Use serial wiring if your panels are butt together or very close to each other

Your panels are butt together, so just wire them in series. Short wire run to MPPT controller only one + & - into controller . Simple.

[ChuckSK]

Here are 2 more graphs. They show the effect of shading a cell in 2 different panels.





The bottom line is that with a series connection shading a cell takes out the sub-panel whereas with a parallel connection shading a cell takes out the entire panel.

I think I'm done now.

Chuck

[s/v Jedi]

Originally Posted by ChuckSK

Here are 2 more graphs. They show the effect of shading a cell in 2 different panels.

Attachment 37400

Attachment 37401

The bottom line is that with a series connection shading a cell takes out the sub-panel whereas with a parallel connection shading a cell takes out the entire panel.

I think I'm done now.

Chuck

You did great Chuck and your data is correct, as was that from others who put in the effort to study and test this and report it here. It's a shame that people believe we are trying to sell snake oil, but anything we say will only result in more conspiracy theories of geeks trying to fool the sailors out of some power efficiency of their solar panels. I was about to write a post about reasons why manufacturers add bypass diodes (a huge hint to connect them in series if I ever saw one) to their panels but when even straight test results are ignored, reasoning with logic has no chance either

So I'm done too; I'll just repeat the series=better info whenever the thread needs it

ciao!
Nick.

[prroots]

Originally Posted by Cotemar

Here are the two rules most are following:
Use parallel wiring if your panels are in two locations, far apart.
Use serial wiring if your panels are butt together or very close to each other

Your panels are butt together, so just wire them in series.

Thanks, but I don't believe it As others have said this is a complicated business and the shadows created by every boat are different. I'm not even sure how you arrive at that opinion. If you think that because the panels are adjacent they share the same shading that would be dead wrong. If you think that those rules apply to simplify the wiring, that would be an over-simplification and lead to loss of output in many instances. The wiring to my panels is virtually identical in both series and parallel modes in terms of the number of cables and their length ie, one duplex run from controller to panels. I switch back and forth via 2" jumper(s) on the terminal strip. If you want me to post a simple schematic let me know.

[prroots]

Originally Posted by ChuckSK

Here are 2 more graphs. They show the effect of shading a cell in 2 different panels.

The bottom line is that with a series connection shading a cell takes out the sub-panel whereas with a parallel connection shading a cell takes out the entire panel.

I think I'm done now.

Chuck

Thanks for your contribution. Not only that, but the IV curve for the parallel connected panels would confuse many (esp. the cheap) MPPT controllers.
Pete

[Cotemar]

prroots,

You are doing all the right things. Large wiring and you have a MPPT controller.
Do what you feel is right because in the end you are going to have a sweet solar panel setup and your batteries will be topped off by 11am every day.
You are beating yourself up for such a small number that you’re missing the big picture. After two weeks you will forget you even have a solar panel system, because they just work. They are quiet and maintenance free. What more could you ask for. If you want to squeeze another penny out of it. Give me your address and I will send you a whole bag of pennies.

[goboatingnow]

I know is being said, the shaded output of series panels, with bypass diodes , can only be realised by using MPPT controllers, as the PV curves moves significantly. Whereas in parallel configuration while you loose a panel , theres less effect.

This is often where I think the confusion lies.

The other thing myth to kill is that MPPT controllers do not put out pulsed DC, they are just switched mode DC DC convertors, The output is pure DC with a ripple that is a small percentage of the output voltage.

I can't imagine anything other then very small cells have not had bypass diodes in them since the dawn of panels. Byepass diodes are for string hot spot elimination and would have to be present in any large strings.

Any all this confusion is what you get when you try and connect current sources in series!!!

Dave