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That is what we did for our home system. The main impetus was to keep the
batteries charged without having to charge from the grid using the
on-board battery chargers. Grid charging uses a lot of utility power.
<br><br>
This system has stacked Outback inverters. We keep the backup inverters
turned off at the Mate, but with the instrumentation running. If we did
have a low battery situation, the voltage would rise enough to start the
system back up from the 80 W of DC coupled PV. <br><br>
Another way to recover from low battery shutdown would be to program the
shut down parameters below battery voltage when the sun came back out.
Also, it is likely that if the system were completely turned off at the
DC breaker, the battery voltage would rise enough to start the
inverter(s) when solar resources improved. <br><br>
At 05:51 PM 6/6/2015, you wrote:<br>
<blockquote type=cite class=cite cite="">Years ago, when I was
researching SB/SI microgrid solutions for a Ted Turner high-end off grid
rich man's lodge, John Berdner (at that time the head of SMA-America) had
made me the same recommendation: that a small amount of PV be wired as a
DC charge-controller-based input. This was a final fail-safe approach, in
case the array was insufficient and the gennie didn't start. It would
bring the batteries to a minimal voltage level, such that the SB/SI
system would return to operation once the batteries recovered.<br>
Allan<br><br>
<b>Allan Sindelar</b><br>
<a href="mailto:allan@sindelarsolar.com">allan@sindelarsolar.com</a><br>
NABCEP Certified PV Installation Professional<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder (Retired), Positive Energy, Inc.<br>
<b>505 780-2738 cell</b><br><br>
<br>
On 6/6/2015 8:23 AM, Mac Lewis wrote:<br>
<blockquote type=cite class=cite cite="">Hi Mark, <br><br>
The Sunny Island has various battery protection modes and will shutdown
based on user programmable state of charge levels. Level 2 battery
protection will start the Sunny Island every 2 hours in an attempt to get
charge into the batteries. You should set this level up at times
when energy input is likely. See page 113-114 here:
<a href="http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-20.pdf">
http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-20.pdf</a> If it
doesn't get any charging to the batteries for 10 minutes, it will shut
down and wait again.<br><br>
This is an advantage of having at least some DC coupled solar
input.<br><br>
<br><br>
On Sat, Jun 6, 2015 at 7:39 AM, Mark Frye
<<a href="mailto:markf@berkeleysolar.com">markf@berkeleysolar.com</a>
> wrote:<br>
<dl>
<dd>Hi Guys,<br><br>
<dd>Just wondering about how a SI/SB microgrid works. If all the PV is
connected to SB inverters, what happens if the loads manage to drain the
batteries to their low voltage shutdown? Wouldn't the SB stop providing
the AC sync so then the SB wouldn't have anything to sync to even if they
had power available from the PV?<br><br>
<dd>How is this handled? It seems to me you would always want to have
some amount of PV DC coupled.<br><br>
<dd>Thanks,<br><br>
<dd>Mark Frye<br>
<dd>Berkeley Solar Electric Systems<br>
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-- <br><br>
<font color="#305A78"><br>
</font><br>
Mac Lewis<br><br>
<font face="Verdana">"Yo solo sé que no sé nada."
-Sócrates<br>
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