MIXED PANEL ARRAY'S [RE-wrenches]

[Steve Willey, Backwoods Solar]

TC:
Yes observed and discussed with RV power.  The solarboost 50 will use a bit
of power especially in the voltage conversion mode and it stops converting
voltage and stops boosting and just passes straight through at low power
levels in the area of 3 amps plus or minus one.  This is not significant
when not converting voltage, just loses the boost function, but in 24 to 12
you actually get less power out to battery than in from array at low amp
levels.  If you have a smaller array, like well under the capacity of the
Boost 50, then it will spend more time below the conversion and boost
threshold than a larger array.  at some point the boost unit is not going to
be effective.  I fear that effect combined with the amorphous lower PPP will
cause you to gain little from the extra cost of the boost.  However if
future higher power array is expected, then only the amorphous part is to be
considered.

I thought the Siemens instruction sheet limit on not paralleling modules was
discussed earlier on this group and decided the instructions were obsolete,
per the factory, and it indeed was permissible to parallel two modules??? ??

Steve Willey   www.backwoodssolar.com
Backwoods Solar Electric Systems

----- Original Message -----
From: Travis Creswell, Ozark Solar <ozsolar at ipa.net>
To: <RE-wrenches at topica.com>
Sent: Monday, August 14, 2000 1:31 PM
Subject: Re: MIXED PANEL ARRAY'S [RE-wrenches]


> Steve
>
> I'm not sure what you are saying.  Is this something you have seen as I
> don't think it would matter how large the array other than the the Solar
> Boost 50 itself would represent a larger draw on a smaller array.  The
main
> reason I am considering going to 24 volts is to leave as much room in the
> future for expansion. They are talking about wanting to be able to charge
to
> Campground host's RV batteries as well.  Also, to meet code you can never
> parallel modules so I have to pull wires for all 6 modules to the combiner
> box.  I just as soon pull 3 runs instead of 6 runs.
>
> As I understand MPPT there is not much potential for boosting during warm
> weather and as batteries get fully charged.  The colder the weather the
> higher the panels voltage gets this the more potential for boost.  It
makes
> sense that the UniSolar amorphous products don't have much application for
> MPPT as their MPP is pretty low to begin with.
>
> Thanks
> Travis Creswell


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