<html><body style="font-family: Helvetica,Arial,sans-serif; font-size: 12px;"><div>I agree completely that AC coupled systems are far better off if they have a battery charging method completely independent of the off-grid inverter. Some DC coupled solar is the best way to go. The system I'm considering already has 2820 W of DC coupled PV. <br></div><div><br></div><div>Drake<br></div><br><br><blockquote class="atmailquote"><br>----- Original Message -----<br><div id="origionalMessageFromField" style="width:100%;display:inline;background:rgb(228,228,228);"><div style="display:inline;font-weight:bold;">From:</div> "RE-wrenches" <re-wrenches@lists.re-wrenches.org></div><br><div id="origionalMessageToField" style="display:inline;font-weight:bold;">To:</div><re-wrenches@lists.re-wrenches.org><br><div id="origionalMessageSentField" style="display:inline;font-weight:bold;">Cc:</div><br><div style="display:inline;font-weight:bold;">Sent:</div>Thu, 31 Oct 2019 19:33:11 -0600<br><div id="origionalMessageSubjectField" style="display:inline;font-weight:bold;">Subject:</div>Re: [RE-wrenches] Off Grid Optimizers<br><br><br><p>We've discussed AC coupled many times. Aside from the issues
Michael brought up, I need to remind that not having at least some
DC PV charging means that when the AC system shuts down for any
reason, so does all the PV charging. If Li+ batteries get
discharged to their low voltage shut off: Dark Starts anyone?
With lead acid, DC coupled PV is just as critical to keep the
battery from sulfating.<br></p>
<p>Which would you want? <br></p>
<p>Scenario 1:Come back to trouble shoot a system shutdown, try to
reboot, only to find no battery voltage to even test with. or <br></p>
<p>Scenario 2: You will have a battery that is being charged, if
not already at full charge.</p>
<p>For GTB?, you decide how important this issue is, but for Off
grid you are putting your customer in serious jeopardy without
power. Unless they have a manual bypass, the generator won't pass
through to the loads, or charge the battery either. This is not
theory, We've had to fix these, and in some cases replace the
battery bank that was damaged after sitting dead too long.</p>
<p>My previous post in favor of AC coupling was only as a supplement
to a solid DC PV system, or for module level optimization in
partial shade conditions. <br></p>
<pre class="moz-signature">Ray Walters<br><br><br>
Remote Solar<br><br><br>
303 505-8760</pre>
<div class="moz-cite-prefix">On 11/1/19 1:08 PM, Michael Morningstar
wrote:<br></div>
<blockquote>
You know Murphy? That is Murphy of Murphy\u2019s Law? He\u2019s gotta just
love the idea of AC coupled off-grid systems. The OB, SB, Li
system Jay described is going to keep him (Murphy) and the
installer very busy at some point. The further away the system is
from civilization, the higher the odds of chicanery and headaches.
Systems that need backup safety controls seem inherently risky
too.
<div><br></div>
<div><br><div><br><blockquote>
<div>On Oct 31, 2019, at 11:06 AM, jay <<a href="mailto:jay.peltz@gmail.com">jay.peltz@gmail.com</a>>
wrote:</div>
<br class="Apple-interchange-newline"><div>
<div>HI Drake,<br><br>
I was just talking with a colleague the other day about
a project he did. <br>
New Radian, AC coupling, lithium batteries, SB
inverters. Everything is working just as it should with
the GT inverters tapering during AC coupling frequency
shift mode.<br><br><br>
I would say you are fine, and while I can\u2019t say for sure
if the Enphase will work that way, they should as they
are all designed to the same parameters rule 21. <br><br>
I always do recommend a aux relay for backup/shutoff
should there be some kind of issue. <br><br>
With the Envoy you\u2019ll be able to see that tapering as
well.<br><br>
Seems like a good option for your application<br><br>
jay<br><br><br><br><br><br><blockquote>On Oct 31, 2019, at
9:49 AM, Drake <<a href="mailto:drake.chamberlin@redwoodalliance.org">drake.chamberlin@redwoodalliance.org</a>>
wrote:<br><br>
Hi Jay,<br><br>
Between 2160 and 2880 Watts of added array. We will be
using a new Radian.<br><br>
Drake<br><br>
At 11:49 AM 10/31/2019, you wrote:<br><blockquote>How many watts are
you adding as ac coupling?<br>
And presuming its an older 8k radian?<br><br><br>
Jay<br><br>
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