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View Poll Results: In a 12V boat with 2- 32Vmp panels using a MPPT controller, with "oversized" wiring
Series 4 23.53%
Parallel 12 70.59%
wouldn't make a difference overall 1 5.88%
Voters: 17. You may not vote on this poll

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Old 23-11-2018, 13:32   #1
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Series/Parallel with High Volt Panels

I'm about to redo my solar. Yes this question has been asked, but reading the threads they blog down too much in bickering. So:

In a 12V boat with 2- 32Vmp panels using a MPPT controller, with "oversized" wiring -

What's better for handling "some" shading to 1 panel - panels in series or panels in parallel.
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Old 23-11-2018, 15:11   #2
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Re: Series/Parallel with High Volt Panels

My approach would be to get a separate controller for each panel. That is my plan. All components purchased but farther down the to do list sadly.
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Old 23-11-2018, 15:18   #3
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Re: Series/Parallel with High Volt Panels

Pretty sure this is straightforward, go with parallel. Or better yet, one MPPT per panel.
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Old 23-11-2018, 15:19   #4
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Re: Series/Parallel with High Volt Panels

Its a no brainer!

If panel voltage is sufficient for Batt's/DC Buss, parallel is the only way to go.
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Old 23-11-2018, 16:26   #5
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Re: Series/Parallel with High Volt Panels

This shows a good demonstration.
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Old 24-11-2018, 10:00   #6
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Re: Series/Parallel with High Volt Panels

LOL-This is the number one question asked by our customers and there is no black-and-white answer. Simply put it depends on the location of the solar panels, quantity and the rating of the charge controller. The short answer is if you are using panels that are rated "12V" chances are they are a 18 to 20 Vpp panel and work well with most low-cost controllers but have limited voltage headroom to maximize the advantage of MPPT and energy harvest. Better to configure the solar system for a higher voltage and use a higher voltage rated MPPT controller. Be forewarned, once you get above 50VDC it becomes a dangerous situation on board a boat and extra precautions should be taken. Always be sure your fixed frame solar panels are connected to ships ground for safety reasons. Additionally be sure that the maximum input voltage of the charge controller is always greater than the solar panel system Voc by at least 15%.
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Old 24-11-2018, 10:12   #7
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Re: Series/Parallel with High Volt Panels

In panels that get any shade, or are not facing the exact same direction. You do not want series.
(So basically all boats. Good for a house roof with no trees ). Because any shade screws up all panels.

Panels not facing the exact same dir. you do not want parr. Because each panel will have a different peak voltage level if facing different directions.

Some boats do this and some don't.


On a boat. You generally want one countroller per panel for max output from each panel
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Old 24-11-2018, 11:17   #8
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Re: Series/Parallel with High Volt Panels

To supplement the single 130W panel [on top of the bimini] that came with the boat when we acquired it, I installed two 165W panels on top of the dinghy davits on our ketch. [They can be pivoted— as a single rigid assembly— on an athwartships axis to maximize solar gain.]

Each panel [3] has its own 75V/15A Victron MPPT controller [with built-in bluetooth.] Observing the live and historical data from the controllers for the two side-by-side 165W panels, there are many times when one panel has some shading [e.g., mizzen mast, standing rigging, etc.] and consequently, greatly diminished output. In these circumstances, the unshaded panel is providing much higher output.

It is worth noting that two of the above linked Victron 15A controllers cost about the same as one Victron 30A controller at the time, so controller cost was not a deciding factor in this case. [US$10 total savings on 1 vs. 2 controllers...]

For me, having a controller per [larger] panel is worthwhile redundancy as well.

In case this is helpful.

Cheers! Bill
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Old 24-11-2018, 11:29   #9
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Re: Series/Parallel with High Volt Panels

Trick question without enough information. This is why discussions bog down. Generally the answer is parallel, but...
  • How much shading? A wire hardly matters either way.
  • What portion of the panel? The video showed that column vs. row gives a different affect. One favors parallel, the other series.
  • Do you mean sharp shadows or diffuse, like clouds? Bird bombs? Or a dodger? Sharp affecting only one panel favors parallel, but diffuse affecting all of the panels favors series.
So much for a simple answer.
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Old 24-11-2018, 13:46   #10
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Re: Series/Parallel with High Volt Panels

I asked the parallel / series question of the Victron rep at the Newport Boat Show. He pointed out that when using a Victron MPPT a major factor is making the charging day start earlier and extend longer. The Victron charger starts when the voltage is greater than 5 volts above the battery voltage. In series the voltage is above the threshold soon as you get sunshine. In parallel the voltage can be on the edge until the sun is further up.
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He wasn't saying that the effect of shadowing wasn't important just that voltage made a
significant difference.
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Old 24-11-2018, 14:03   #11
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Re: Series/Parallel with High Volt Panels

I knew people would see if they could make it more complicated than needed. I had my old 290W panel with my Outback FlexMax 60 controller on the boat for 6 years, including 2 years full time cruising/liveaboard. I pretty much know the effects of shading on the performance and the position/mounting of my new 610W system is pretty much the same location just with the panels mounted fore/aft instead of awthship. So pretty much 1 of the new panels might see the worst shading that the old panel ever saw (in general because you don't get to chose wind directions).

I also could switch from parallel to series in about 3 minutes
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Old 24-11-2018, 14:27   #12
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Re: Series/Parallel with High Volt Panels

Quote:
Originally Posted by sailorboy1 View Post
…I also could switch from parallel to series in about 3 minutes
This would be an interesting experiment.

A friend, who is a marine electronics expert and installer, actually tried both series and parallel with his panel setup. His report was that neither was a clear winner. His panels don't experience much shading — not nearly as much as mine do.

Of course, how each solar system functions is dependent on each individual setup. Not just panel shading, series/parallel, but also how big the battery bank is and the type of daily drawdowns, and probably a whole lot more I’m not thinking of. Hard to make blanket statements.
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Old 24-11-2018, 14:45   #13
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Re: Series/Parallel with High Volt Panels

Ok going into controllers. Assume a battery bank of 450ah and 3 panels with 300 watts solar: a 15amp verses a 60amp controller. If money was no issue is bigger necessarily better?

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Old 24-11-2018, 15:25   #14
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Re: Series/Parallel with High Volt Panels

Quote:
Originally Posted by sailorboy1 View Post
I knew people would see if they could make it more complicated than needed. I had my old 290W panel with my Outback FlexMax 60 controller on the boat for 6 years, including 2 years full time cruising/liveaboard. I pretty much know the effects of shading on the performance and the position/mounting of my new 610W system is pretty much the same location just with the panels mounted fore/aft instead of awthship. So pretty much 1 of the new panels might see the worst shading that the old panel ever saw (in general because you don't get to chose wind directions).

I also could switch from parallel to series in about 3 minutes
That is true Tom if you are using 12 volt nominal panels. Bump up to a 320w 32v panel and the Victrons kick on right away.
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Old 24-11-2018, 15:25   #15
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Re: Series/Parallel with High Volt Panels

Not a lot of votes, but from the voting it isn't all clear really at 3:6
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