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Old 04-04-2021, 13:54   #1
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New solar installation: series - parallel switch

Hello. I am installing 3 100 watt solar panels on the railings around the fly bridge of our Tollycraft 37 sportfish. There is a bimini (almost always furled up) and a mast overhead so shading will be an issue. My goal was to have two panels in clear sunlight no matter how we are swinging on the anchor.

I can lower the bimini and the mast - like I do to go into the boathouse - and then all three panels are pointing straight up with no shading.

So based on what I've learned here, I want to hook the panels up in parallel if the bimini and mast are up, but in series when they are down to take advantage of the higher voltage in the wires leading to the controller. Is this correct??

My plan was to wire the three panels to two separate 6 position terminal strips and then move the two wires leading down to the controller from the terminal strip that has the panels wired in series to the one where they are wired in parallel.

THEN I thought, why not put a DPDT switch that would switch the two controller wires from one terminal strip to the other.

Does this make sense? Am I introducing too many connections into the system? Is there a better way??

As always, many thanks....
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Old 04-04-2021, 15:29   #2
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Re: New solar installation: series - parallel switch

If some panels are shaded you don’t want parallel or series. You want each panel on own controller. And 3 small controllers is about the same price as 1 big one anyways.
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Old 05-04-2021, 10:37   #3
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Re: New solar installation: series - parallel switch

If some panels are shaded you don’t want parallel or series. You want each panel on own controller.

DOH!! I knew I should have come here first!! Here's what I've done so far. The three panels are mounted. I haven't got the wires coming off the panels yet but my plan was to get the #10 ga wires from the three panels and tie them down on the terminal strips in the 'attic' of the flying bridge right at the top of the pole going down to the engine room. From there I've run a pair of #6 ga wires to the Victron 100 v 30 amp controller and onto the batteries.

If I go with three smaller controllers, they will have to be up on the fly bridge. I would prefer them to be closer to the batteries to take advantage of the higher line voltage when in series but if the three panels are going to be each on their own controller I guess that doesn't matter.

If I do go with three separate controllers, does the Victron app talk to all three and give an aggregate output??
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Old 05-04-2021, 11:39   #4
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Re: New solar installation: series - parallel switch

Quote:
Originally Posted by Perdiem View Post
If I do go with three separate controllers, does the Victron app talk to all three and give an aggregate output??
The total solar production of all controllers is displayed on the Victron app. However, the display is a bit “flakey” with a slow refresh rate and some drop outs. Victron have tried to address this issue with their software updates, but so far no success, at least on my equipment.

Personally, I use the excellent Simarine Pico battery monitor that displays the output of each of the solar panels as well as the net charge/discharge rate.
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Old 05-04-2021, 11:50   #5
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Re: New solar installation: series - parallel switch

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Originally Posted by Perdiem View Post
Does this make sense? Am I introducing too many connections into the system? Is there a better way??
Overall, parallel connection of solar panels usually produces higher net output than series connection on a boat. There are exceptions, but it is not generally feasible to switch between the two alternatives in a practical way.

One controller per pannel is better again, but with only 100w panels you are close level to where this becomes impractical.
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Old 05-04-2021, 12:31   #6
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Re: New solar installation: series - parallel switch

1 controller per panel is the best if you can afford it.

I have always advise doing series wiring with bypass diodes.
https://www.pveducation.org/pvcdrom/.../bypass-diodes

This way your shaded panels dont pull down the system and you can keep the benefits of high voltage low cost wiring. Ensure that your controller can handle the full Voc of your series panels!
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