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BillK avatar image

Best match of panel strings to smart solar charge controller

I am installing 6.3kW of solar panels. The system consist of 18 350w panels, 6 panels on each of 3 pole top arrays. I have to do it this way because I live at at 49 degrees N and there is a slight upwards slope to the south with some fairly tall trees at the top. The panels will be mounted vertically so the top row of panels on all three poles will start generating power earlier than the bottom row. One of the reasons I went with the panels I chose is there ability to start putting out power before the entire panel is in the sun. Starting this month and through mid February this will be a significant advantage for me.

My question is how to connect them to my pair of Smartsolar 250/85 controllers. I will be using 6 strings of 3. Do I make the top row of panels on each pole as one string and connect those 3 strings to one controller? Or is better to try to balance the input so that each controller is getting roughly the same amount of power at about the same time?

smart solar set-up help
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Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@BillK, personally I'd advise running your early-sun panels to one controller and your later-sun panels to the second controller, as I've seen great success in the wild with people splitting up their arrays in this sort of manner... the logic being that the early-sun panels connected to the first controller will be awake and putting out as much power as possible while the later-sun panels on their own controller are still ramping up; and the same in reverse, of course, as presumably your later-sun panels will also be still be in good sun and putting out good power while your early-sun panels are ramping down.

In actual practice, how much difference in total daily harvest you'll see from this method as opposed to a balanced-connection method is debatable, and in fact there's really probably no way to tell without a long-term study under your particular conditions... but if it were my array, I'd definitely connect them separately in accordance with the order in which they'll be seeing sun.

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