Outback 60 with Partially Shaded Panels

[zboss]

Hi,

If want to use a single Outback Flexmax 60 charge controller with four solar panels, I assume that the four panels will be wired in parallel to a bus, which then goes to the controller.

If some of those panels are shaded, while others are not, how will this effect the overall voltage of the system?

Is this an effective method of using our panels? I expect that at least 1 or 2 panels will be shaded during certain parts of the day.

- z

[zboss]

The reason I bring this up is that I currently have one controller for each panel and I wanted to know what kind of difference I could expect.

[Ex-Calif]

I haven't reread this lately but with lots of solar, high voltage controller and series is the way to go.

The controller has a better chance of being able to deliver charge voltage when cells are shaded. Although, of course amperage still suffers.

W = V X I

[roetter]

I run 3 panels in parallel and another 3 in series, each set on one Outback 60. So far I have not seen any significant differences in the daily output averages. Some days the parallel is better, some days the series string. I stll have a plan to do do some detailed test with the set up.

[bobofthenorth]

My advice plus $5 will buy coffee pretty well anywhere in North America but for identical panels I'd wire them in series to an MPPT controller. I think there's a case to be made that they will be more efficient and less subject to shading. Even if none of that is true you will be able to use lighter gauge wire.


R.J.(Bob) Evans
www.travellingwithgeorge.blogspot.com

[mitiempo]

Series works well on land where the panels can be installed with no shading issues. In any installation with shading parallel is the choice to make. Shading a series array kills it. Shading a parallel array reduces output by the shaded panel but not the rest of the un-shaded panels.

[Hkalan]

Hello,

Parallel is by far the best.

I use a Morningstar TS-60 MPPT with a combiner box I made that breaks the + and - to isolate any panel.

[Ex-Calif]

Originally Posted by mitiempo

Series works well on land where the panels can be installed with no shading issues. In any installation with shading parallel is the choice to make. Shading a series array kills it. Shading a parallel array reduces output by the shaded panel but not the rest of the un-shaded panels.

Thanks mitempo you are correct - I made a mistake in my post.

Thanks for chiming in.

[noelex 77]

Originally Posted by zboss

The reason I bring this up is that I currently have one controller for each panel and I wanted to know what kind of difference I could expect.

One controller for each panel gives superior tracking, but the difference is small. The other problem is that the good MPPT controllers have reasonably high self consumption so you can lose more than you gain.

A single good quality controller is the norm and works well.

As you can see there is a lot of debate between series and parallel connection. Unfortunately I don't think there is enough evidence to form a definitive answer, but mine are wired in parallel.

[sailorboy1]

I bet that if multiple panels are smaller 12V panels that wired in series is best. But if higher voltage panels like 24-36V panels that it doesn't matter much.


Sent from my iPhone using Cruisers Sailing Forum

[Dulcesuenos]

We have 6 panels paralleled together, no combiner box, to one controller, and very pleased with it

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[mitiempo]

Originally Posted by sailorboy1

I bet that if multiple panels are smaller 12V panels that wired in series is best. But if higher voltage panels like 24-36V panels that it doesn't matter much.

Wired in series a shaded panel is a roadblock. Not unlike the old series Christmas tree bulbs. Parallel will not stop a good output panel from passing through the connections of a shaded panel. In series the current has to pass totally through the shaded panel, which it cannot do. Pretty basic really.

Now on a powerboat's upper deck without any possibility of shadowing series works well.

[noelex 77]

Originally Posted by mitiempo

In series the current has to pass totally through the shaded panel, which it cannot do. Pretty basic really.

All solar panels have bypass diodes. As the name suggests these function to bypass the current around the shaded cells (with some losses).

[zboss]

I was observing our panels and because of the limitations on our cabo, we only see 1 out of 4 panels completely unshaded during the day, except for about an hour on each end at peak solar high, during which we have four panels going string. The 4th panel then becomes the primary panel when the sun moves across the sky or we swing due to current.

[mitiempo]

Originally Posted by noelex 77

All solar panels have bypass diodes. As the name suggests these function to bypass the current around the shaded cells (with some losses).

For a 36 cell panel there are usually 2 bypass diodes. Still adds up to a loss if multiple panels are in series. Parallel doesn't have any issues with current from one panel passing a shaded panel.