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I have an array consisting of ten solar panels wired in series as shown in the figure below:

enter image description here

My problem is that during some winter months (Oct - Dec maybe), in the afternoon, the sun is so low that the shadow of a building to the south will reach my roof. This means that there is a time interval during the day when the lower lane of panels will be shaded while the top will face the sun, as shown in the figure below.

enter image description here

My question is: Do I need to install additional bypass diodes to keep the lower panels from degrading? If so do I add one to each panel or just a single diode parallel the five lower panels?

I understand that the panels already have bypass diodes in their junction box, but I am not sure whether they are rated high enough for this arrangement. The panels are LG Mono X 300 Watt panels. The open circuit voltage of the entire string is around 330 Volts when the entire array is unshaded and the operating voltage of the whole string is above 120 Volts when it is partially shaded as in the figure above.

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