shade

felix · July 2016

I have 3 panels, one will be in the shade part of the day. what is the beste way to connect them

vtmaps · July 2016

What are the specs on the panels, what controller are you using, and what is your battery voltage? --vtMaps

felix · July 2016

felix · July 2016

http://suncalc.net/#/56.193,10.6821,11/2016.06.11/12:31
midnite solar Charge Controllers - KID
24 v

vtmaps · July 2016

You did not answer my question about the battery voltage or controller, but I see from your other thread that you have a 24 volt system. Generally, when shade is an issue you are batter off with the panels in parallel. However, your panel voltage (in parallel) is not high enough to charge a 24 volt battery. You need to put two panels in series and use a MPPT type controller.

--vtMaps

felix · July 2016

midnitesolar Charge Controllers - KID

24v

BB. · July 2016

Assuming that you have the choice of 3x in series (one string), or 3x parallel connected in parallel... And you do not have a long run from the solar array to the charge controller--Then I would suggest 3x in parallel. I do not like running the current through the bypass diodes on the "dark" panel (diodes run hot and can fail).

Of course, if you have three panels in parallel, you should use a combiner box plus 3x fuses or breakers.

And because you are running Vmp~31 volt panels on a 24 volt battery bus--You need to run (at least) two panels in series at a time to get Vmp-array>=35 volts. A single Vmp~31 volt panel is too low of voltage on an operation system (Vmp-hot will fall as low as ~25 volts, and your 24 volt lead acid battery bank needs around 29-32 volts for proper charging+voltage drop for wiring).

So, your present choice is 3 panels in series (not great, for first reason), or have 2x panels in series by 2x parallel strings for four panels total--Which you presently do not have.

-Bill

felix · July 2016

which combiner box should I buy

vtmaps · July 2016

felix said:

which combiner box should I buy

What are you planning to combine? Three panels in parallel, (which won't be high enough voltage) or four panels in a series/parallel configuration? If the latter, you don't technically need a combiner box or circuit breakers, but it is a great convenience to have them for troubleshooting.

--vtMaps

felix · July 2016

I only have room for Three panels and should have most of them

BB. · August 2016

I double checked using the Midnite Kid string sizing tool:

http://www.midnitesolar.com/sizingTool_kid/index.php

And it looks fine to have all three panels in series. Of course, if there is anything you can do to change the shading on the third panel--I would suggest doing what you can (trim tree, move vent pipe, etc.).

Because they will be 3x in series--You do not need a combiner box.

-Bill

felix · August 2016

Maybe I should buy a kid more it is almost as expensive as a combiner box.

vtmaps · August 2016

felix said:

Maybe I should buy a kid more it is almost as expensive as a combiner box.

I suggest that you buy a midnite brat for your one shaded panel, and put the other two panels in series to your midnite kid. The shaded panel will help you bulk the batteries, although because the panel voltage is low, it may not be contribute much to absorb or equalization. Hopefully the shade occurs in the afternoon, after bulk is complete.

--vtMaps

shade

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