<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Ray,<div class=""><br class=""></div><div class="">I’m curious about what you mean by not doing a 3 stage charge. While PV charging in coupled mode (off grid), the battery will reach your absorption set point. Is this triggering the GT inverters to shut off or does the battery inverter absorb timer run at all? I would think the absorb timer should run until the array current produced is more than being consumed and then the the GT shuts off.</div><div class=""><br class=""></div><div class="">Just a wild idea here but if you could calculate the AH needed to reach 100% SoC after the GT inverters shut down, a separate PV array and charge controller would stay online to finish the charge. No wasted energy to dump loads and the customer has more usable power from the system. This may cost more than going to a dump load though.</div><div class=""><span style="orphans: 2; text-align: -webkit-auto; widows: 2;" class=""><br class=""></span></div><div class=""><span style="orphans: 2; text-align: -webkit-auto; widows: 2;" class="">Larry </span></div><div class="">
<br class=""><div><div class="">On Aug 20, 2015, at 10:56 PM, Ray Walters <<a href="mailto:ray@solarray.com" class="">ray@solarray.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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Hi Folks;<br class="">
<br class="">
I've done more research on the whole AC coupled issue, and one flaw
I found with both the Sunny Island and the Radian is that they can't
really do a full 3 stage charge for the batteries in off grid mode.<br class="">
They detect that the batteries are full and disconnect the AC
coupled GT inverters, but this is about as subtle as the very early
charge controllers, and amounts to 1 stage charging. This is fine
for temporary outages, and when the grid comes back, the batteries
get a good 3 stage charge. But these folks are really wanting a
design that could be taken off grid permanently. Also as you my
recall, the GT PV system is Enphase, so we can't use the more
sophisticated controls that SMA offers for the Sunny boys. <br class="">
I hate to say it, but I might be back to a diversion load with PWM
controller. Not elegant, but we could get 3 stage charging. <br class="">
Every time I look at AC coupled setups, I just want to start over
with charge controllers. <br class="">
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
<div class="moz-cite-prefix">On 8/17/2015 9:39 PM, Mac Lewis wrote:<br class="">
</div>
<blockquote cite="mid:CAOABG4_E0OWuKThmiVmhtvkfY0XDHO7Kf3+A8-=EKVvPn_ZX0g@mail.gmail.com" type="cite" class="">
<div dir="ltr" class="">Hi Ray,
<div class=""><br class="">
</div>
<div class="">With that size grid-tied system, you would want to use a
battery based inverter(s) near the (6.7/0.8) 8000W range. </div>
<div class=""><br class="">
</div>
<div class="">The frequency shift of the Sunny Islands will work with
kicking out the enphase inverters but you wouldn't get the
same output ramping that it would offer if it was a Sunny Boy
grid-tied inverter. The Sunny Island can effectively solve
your generator backfeeding because there is a reverse current
sensor that will disconnect the AC input at whatever level you
want, 50 mA is default I think. You may need to give the
Sunny Island generator start control for this however.</div>
<div class=""><br class="">
</div>
<div class="">You can read about it here on page 137.</div>
<div class=""><br class="">
</div>
<div class=""><a moz-do-not-send="true" href="http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-21W.pdf" class="">http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-21W.pdf</a><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">You'll need to give the Sunny Island a digital signal that
tell it whether its connected to a generator or a grid as
outlined in the manual. </div>
<div class=""><br class="">
</div>
<div class=""> This is where the Radian is nice because it has two AC
Input terminals.</div>
<div class=""><br class="">
</div>
<div class="">Sounds like an interesting project.</div>
<div class=""><br class="">
</div>
<div class="">Good Luck.</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
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</div>
<div class="gmail_extra"><br class="">
<div class="gmail_quote">On Mon, Aug 17, 2015 at 8:36 PM, Jerry
Shafer <span dir="ltr" class=""><<a moz-do-not-send="true" href="mailto:jerrysgarage01@gmail.com" target="_blank" class="">jerrysgarage01@gmail.com</a>></span>
wrote:<br class="">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr" class="">I cant see this working well without some
battery based inverter<span class="HOEnZb"><font color="#888888" class=""><br class="">
Jerry</font></span></p>
<div class="HOEnZb">
<div class="h5">
<div class="gmail_quote">On Aug 17, 2015 10:10 AM, "Ray
Walters" <<a moz-do-not-send="true" href="mailto:ray@solarray.com" target="_blank" class="">ray@solarray.com</a>>
wrote:<br type="attribution" class="">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">HI
Esteemed Wrenches:<br class="">
<br class="">
I am consulting on a system I have never seen, that
consists of a 6.7Kw Enphase roof mounted system, and
2 backup generators. Each generator has an
automatic 200 amp transfer switch to back up its own
200 amp panel. Both 200 amp panels are fed by a 400
amp service from the grid.<br class="">
The Enphase PV backfeeds a subpanel in another
building which then is fed by a 2 pole 60 amp
breaker in one of the 200 amp panels.<br class="">
Currently they are having issues with the generators
kicking out because of the Enphase inverters. That
part I understand: you can't backfeed a generator,
or its voltage regulation freaks out.<br class="">
<br class="">
Now we get to the fun part: they want to create a
third critical load subpanel with loads selected
from both 200 amp panels to be powered by batteries
and an inverter.<br class="">
I am considering the Sunny Island since it makes the
most sense with its ability to signal the Enphase
inverters to shut off when the batteries are full.
I also see this as a partial solution to the
generator issue, since normally the Enphase will be
connected to the output side of the Sunny Island.
However, when the generator is used to charge, we
will be back to directly coupling the generator
output to the Enphase.<br class="">
<br class="">
Here are some possible solutions I'm considering:<br class="">
1) Use a separate charger for the generator so that
it will only feed DC to the batteries, and not be AC
coupled.<br class="">
2) convert the PV back to DC with charge
controllers, but that would involve ditching and
adding another conduit run between buildings.<br class="">
3) Put the Enphase PV on a relay that would
disconnect the PV when charging with the generator.<br class="">
4) Something I haven't thought of that one of you
clever folks can suggest......<br class="">
<br class="">
As always, thanks in advance for all you responses,<br class="">
<br class="">
-- <br class="">
R.Ray Walters<br class="">
CTO, Solarray, Inc<br class="">
Nabcep Certified PV Installer,<br class="">
Licensed Master Electrician<br class="">
Solar Design Engineer<br class="">
<a moz-do-not-send="true" href="tel:303%20505-8760" value="+13035058760" target="_blank" class="">303 505-8760</a><br class="">
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