Solar panel setup opinions/advice wanted…

bradbill

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Jun 6, 2021
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Renogy's website states their 100W panels have bypass diodes.

It would be really interesting to see real numbers on actual voltages and amperages (and resulting wattages) on 2 panels in series vs 2 panels in parallel with various shading patterns applied to the two pairs of panels. That might help narrow down which shading patterns would indicate using serial panels versus which patterns are better handled by parallel panels.
You also have to take into account that early in the morning and later in the afternoon, panels in series will still have enough voltage to keep your solar controller running. It's almost always better to run panels in series
 

sunshine_eggo

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You also have to take into account that early in the morning and later in the afternoon, panels in series will still have enough voltage to keep your solar controller running. It's almost always better to run panels in series

Disagree with the generalization. Early morning and late afternoon don't have much power to deliver even if the panels can muster big voltage. If you have a 40Vmp panel on an MPPT charging a 12V, there's nothing meaningful to be gained by 80V or 120V. In fact MPPT lose efficiency the greater the DC conversion.
 

bradbill

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Disagree with the generalization. Early morning and late afternoon don't have much power to deliver even if the panels can muster big voltage. If you have a 40Vmp panel on an MPPT charging a 12V, there's nothing meaningful to be gained by 80V or 120V. In fact MPPT lose efficiency the greater the DC conversion.
I am a CEO and CTO for a company that makes small DC to DC converters, that go on circuit boards. You have citation for this "fact" that the efficiency goes down as the voltage goes up?
 

Bud Martin

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Post #12

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brb58

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Mar 17, 2021
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Would be interesting to see what a Victron solar controller chart looks like. A lot depends on the design of the DC to DC converter.

Personally, I would always run panels in series vs parallel if the panel voltage is 20V for a 12V battery system. As already noted, bypass diodes make the shading issue between series an parallel not an issue.
 
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