Two arrays one scc

[evad]

I am planning for two arrays one facing east and one west the size of all in one has one mpp input. What would be the best way to handle this?

 

[gnubie]

Unless you get another MPPT controller and tack that onto the battery the only option is to parallel the strings. I'd put a blocking diode in line with each string but that's not strictly necessary.

Check your local regulations, assuming you care. In some areas you can't have a single array with strings in different planes.

 

[evad]

Am I correct that if the strings are in parallel the lesser will pull down the greater ?

 

[gnubie]

If the two strings are the same voltage ie, same number of identical panels, the Voc of both will be comparable at all times so the array will tend to stick around the optimal point for both strings. If they aren't the same the controller will find the optimum point, with in the abilities of its MPPT algo, and sit there instead. That will be somewhere between the two string's Vmp.

 

[mrdavvv]

I'd put a blocking diode in line with each string but that's not strictly necessary.

So one array doesnt send current to the other?.

 

[gnubie]

Yes, but if they are identical strings it won't be a problem at all, and it's not even a big issue unless the configuration is silly.

It also protects against a severe fault in one string drawing power from the other. That's not a common problem but it will let you get more power from the array should that ever happen, until the fault can be fixed.

 

[evad]

In my situation at the beginning and end of the day one side will have no direct sunlight. So are you saying that there will be a effect but it not enough to add a second scc?

 

[gnubie]

Yes, there will be an effect but I don't think you'd benefit a whole heap from a separate controller so long as both strings are the same number of the same panels. If practical make the wires from the two strings the same length as they go back to the point where they are wired in parallel. Depending on the slopes the panels will heat at different rates as the sun moves across the sky and that will change each string's Vmp so the array will never be at it's peak but it'll be pretty good.