MIXED PANEL ARRAY'S [RE-wrenches]

[Kurt Nelson, SunWise]

Greetings Wrenches,

We have a number of different topics happening under the "Mixed Panels
Array" subject heading.  I am "responding" to Steve's last addition to the
topic in part to thank him for his most exellent and dedicated contributions
to this and other topics.  I also wanted to bring some of this discussion
back to arrays composed of mixed and varied panels.  

Down at the "Shop", I have an array composed of a some Arco 16-2000 33 cell
panels, as well as a couple 36 cell panels.  This year, I added an SP-75 to
the system that is mounted on the inside of the door in such a fashion that
I swing it out and flip it up when I open the shop.  I then have some meters
(volts/amps) and a couple switches that allows the visiting folks to play
with Solar by switching through some loads (water pump and such) or back to
the main shop/battery system to learn about solar.  I have noticed that when
the new Siemens panel is on the system, and the charge regulator
(down-stream) regulates, the amp meter that is on the SP75 indicates about
one amp output.  Is this feeding back into the 33 cell panels?  Initially I
decided this was the case, but is this a factor of higher (Voc) voltage?  If
any such panel (12VDC nom. into 12VDC battery) is connected directly to a
battery, we see something in the way of 35mA out of the array at night.
Does the PV start to see increased reverse current flow when subjected to a
higher voltage than the panel's rated voltage or even PPP voltage?  Why
would I be seeing something approaching 20 watts going back into this little
33 cell array when a twelve volt battery doesn't put but a trickle back?

Thanks for your responses,

Kurt Nelson

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