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Old 28-06-2014, 13:28   #1
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Solar panels and shadow protection

In my preliminary study I have learned that the solar panels must have shadow protection otherwise it can discharge instead of charge the batteries. Does the shadow protection a feature to the solar panel itself or is it (can it) be a feature of the charge controller?

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Old 28-06-2014, 13:33   #2
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All the solar panels I've ever owned and it's been quite a few over the years had a built-in diode that prevents drain and protects the panel. If you have several panels hooked in parallel you need a diode on each panel

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Old 28-06-2014, 13:47   #3
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Re: Solar panels and shadow protection

Likewise, every charge controller I have seen has an automatic disconnect when the panel output is zero.


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Old 28-06-2014, 14:31   #4
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Re: Solar panels and shadow protection

So called shadow protection is actually there to protect be PV cells from becoming biased incorrectly


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Old 28-06-2014, 22:33   #5
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Re: Solar panels and shadow protection

A hugely complicated subject - here is a simply explanation!

There are two functions for the diodes - Blocking Diodes that stop the batteries discharging into the panel at night - and Bypass Diodes that help minimise the effects of shading.

Most large panels don't have Blocking Diodes because a charge controller does the same job.

The more Bypass Diodes in a panel the better - they 'bypass' cells that have a shadow that would otherwise block the current and reduce the output. Ideally all cells would have them but for ease of manufacture 'groups' of cells have a Bypass diode.

It starts getting complicated, and controversial, when you put panels in series or parallel to make a large array and feed an MPPT controller. Many other threads on here and elsewhere arguing which is better - have panels in series to reduce losses in the cables and have a higher voltage at the input to the controller, or have them all in parallel and reduce the effects of shading.

The bottom line is all depends on your panels and how many Bypass Diodes they have - do some long-term tests and see which works best for you on your boat - Series or Parallel!
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