Series or Parallel?

[E350]

NKOTB:  Just a heads up from someone who in 2005 thought as you are thinking now.  I wired in series four 85w BP 380J polycrystaline 17.6Vmp panels on my SportsMobile Voyager roof with Thule tracks using a Xantrex XW MPPT 60 charge controller to 12v 250Ah UPG agm house battery. 

Didn't work well.  I have since learned that my array's output was severely reduced by series wiring vulnerability to shading.  Now I am buying a new controller (probably Kid or Brat) and definitely re-wiring to parallel.

Whatever you do, please post your experience, so we can all learn.

[New KID On The Block]

NKOTB:  Just a heads up from someone who in 2005 thought as you are thinking now.  I wired in series four 85w BP 380J polycrystaline 17.6Vmp panels on my SportsMobile Voyager roof with Thule tracks using a Xantrex XW MPPT 60 charge controller to 12v 250Ah UPG agm house battery. 

Didn't work well.  I have since learned that my array's output was severely reduced by series wiring vulnerability to shading.  Now I am buying a new controller (probably Kid or Brat) and definitely re-wiring to parallel.

Whatever you do, please post your experience, so we can all learn.

Thanks for your input E350.

Shading issue is actually one that I was already aware of and took into account when I started designing my system. My panels are on top of my house roof. There is only shade from a side chimney that affects my series of panels at the very end of day -- right at sunset just before the sun sets. I understand the shade issue with respect to series chain links. I can accept the tiny loss at the very end of day. It's not producing much watts at that time of the day even
with no shading whatsoever.

I'm sure you're well aware of the need for properly sized (read BIGGER) wire gauge cables for parallel hookup.

I'll update with my experience/observations if/when I purchase more panels to add to my system.

[E350]

Oh, I misunderstood this was for a house, there was a mention of an "rv" earlier in the thread.

Also, thank you!  I was not aware of the necessity for larger cables to wire in parallel.  So, if you guys don't mind please tell me what the sizing requirements are. 

This onion seems to peel forever...

[vtmaps]

Also, thank you!  I was not aware of the necessity for larger cables to wire in parallel.  So, if you guys don't mind please tell me what the sizing requirements are. 

There are two sizing issues: ampacity and voltage drop.

When you put solar panels in parallel (like in a combiner), the voltage stays the same, but the current is additive.  The combined output (Imp) of your four panels is about 19.3 amps.  The Isc is a bit higher.

Therefore the wire that runs from the combiner to the controller needs to have an ampacity greater than that.

Suppose you decide that 10 gauge has adequate ampacity to handle the Isc (about 20 amps).  The next question is how long is the wire?  If the 10 gauge wire was 20 ft long (one way), you would have a 4.5% voltage drop along that wire... too much!  Increasing the wire size to 8 gauge would reduce the voltage drop to 2.8%.

--vtMaps

[New KID On The Block]

Oh, I misunderstood this was for a house, there was a mention of an "rv" earlier in the thread.

Also, thank you!  I was not aware of the necessity for larger cables to wire in parallel.  So, if you guys don't mind please tell me what the sizing requirements are. 

This onion seems to peel forever...

E350, the original poster ZoNiE was asking about a setup for his RV. You didn't misunderstand. :-) I happened along and interjected my question into this thread. I hope he doesn't mind. 

You're welcome. It's important to properly size our cables, especially for 12V and hookups chained in parallel fashion. Good luck with your new/redesigned setup.