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We have an AC coupled backup system at our house in S.E. Ohio. In
the winter we have many cloudy days. We are using two 40 W Sunwise
modules in series with a Morningstar PWM CC to maintain a 415 AH, 24 V
set of Full River AGM batteries. We don't need to use the AC charger for
around 1/2 the year. In the winter, we charge regularly from the
grid.<br><br>
Colorado has a <u>lot</u> more winter sun that SE Ohio. If I did ours
over again, I'd double the maintainer array. But we have many periods, of
several days in a row, where it is so dingy that our main array produces
almost nothing, with no snow cover. I've never seen these prolonged, low
light conditions in Colorado. If the price difference for a larger
maintainer array isn't too much, I'd likely go bigger, especially since
your battery bank is twice as big. <br><br>
<a name="_MailAutoSig"></a>Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br>
740-448-7328<br>
</i><a href="http://athens-electric.com/">http://athens-electric.com/</a>
<br>
<br><br>
<br>
At 11:19 PM 10/8/2018, you wrote:<br>
<blockquote type=cite class=cite cite="">Lots of questions this
season..... I'm winterizing a cabin for a customer that will not be there
for the next 8 months (summer use only). Inverter and loads will be off.
The rooftop array will probably be covered with snow for extended periods
of time, and he has a brand new 800 AH set of AGM batteries. I've
read that AGMs can handle sitting for longer periods of time, but my
experience is that they are a bit finicky. I'm planning on adding
a small wall mounted array on a small Morningstar PWM controller that's
sole purpose is to trickle charge the batteries and off set the self
discharge in heavy snow. What is the minimum size array needed?
I've calculated self discharge rates from 2% to 5% /month, and I'm seeing
a very small array would offset that. Even at 5% monthly losses,
and 4 hrs of sun/ day, I'm seeing a 10 watt array could meet that.
My current plan is a pair of 30 watt modules wired in series for the 24 v
battery. Is that too small? Or should I not even worry, because
enough sun will creep through the snow to the main array? Thanks, -- Ray
Walters Remote Solar 303 505-8760
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