sunshine_eggo
Happy Breffast!
This post is WAY less sophisticated than one might think. This deals solely with voltage and amps and how they interact (or don't matter much) in low light conditions.
There have been a handful of posts expressing concern about panels in parallel not playing well together.
This is rarely a concern.
When AMBIENT light hits panels, their voltage increases rapidly even if the light is insufficient to produce any power.
To illustrate this, I disabled my MPPT this morning to capture what happens with the voltage:
The notation is the same minute as sunrise, so anything to the left of that is before direct light hit the panels. These are 3S 72S panels in series. They tend to run Vmp around 120V.
As you can see, before sunrise, even without direct sunlight on the panels, their Voc is above the typical Vmp.
What's the point?
During daytime, even a parallel string in an array in full shade will still be capable of a Voc at or above the Vmp of the parallel string(s) and thus allow the other parallel string(s) to perform at their MPP.
Even weak light gives volts. The intensity of the light allows the panel to to produce amps.
Here's what a morning looks like when the MPPT is working to find MPP as the sun rises:
There have been a handful of posts expressing concern about panels in parallel not playing well together.
This is rarely a concern.
When AMBIENT light hits panels, their voltage increases rapidly even if the light is insufficient to produce any power.
To illustrate this, I disabled my MPPT this morning to capture what happens with the voltage:
The notation is the same minute as sunrise, so anything to the left of that is before direct light hit the panels. These are 3S 72S panels in series. They tend to run Vmp around 120V.
As you can see, before sunrise, even without direct sunlight on the panels, their Voc is above the typical Vmp.
What's the point?
During daytime, even a parallel string in an array in full shade will still be capable of a Voc at or above the Vmp of the parallel string(s) and thus allow the other parallel string(s) to perform at their MPP.
Even weak light gives volts. The intensity of the light allows the panel to to produce amps.
Here's what a morning looks like when the MPPT is working to find MPP as the sun rises:
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