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<p>My advice would be to use a DC charge controller, and forget the
frequency control/ AC coupled goofiness all together. This has
been covered ad nauseam in the past on the list. Its just not a
good idea off grid. I occasionally will design large systems with
some AC coupled array, but only enough to match the daytime AC
loads. Newer AC coupled systems with better communication between
the inverters work better, but if frequency shifting is your main
control, its just never going to work very well.</p>
<p>Besides the issues you're having, you can add poor battery
management and premature cell failures to the list, along with the
unforgivable "Dark Start" when the batteries are discharged below
the LBCO setting. <br>
</p>
<pre class="moz-signature" cols="72">Ray Walters
Remote Solar
303 505-8760</pre>
<div class="moz-cite-prefix">On 11/23/20 8:57 AM, Mac Lewis wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOABG4_K-pOw0B8jfkww9OxntuybchCOyYme6yQMM6yLwNjLrg@mail.gmail.com">
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<div dir="ltr">Hi Chris,
<div><br>
</div>
<div>I have no direct experience trying to troubleshoot devices
that can't handle frequency shift, that seems hard to do.
However, I might utilize a relay approach to solve it. You
could use the relay functions in the Sunny Island to start
dropping strings and/or inverters to keep the frequency shift
from occurring in the first place. There is probably a more
elegant way to do this, but it may work. I believe there is a
way to keep frequency shift from happening in one of the many
setpoints on the Sunny Island. I think this is a serious
disadvantage of frequency shift to control PV output because
so many devices are designed to work at a precise frequency.</div>
<div><br>
</div>
<div>Good luck</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Nov 18, 2020 at 8:09
AM Chris Anderson <<a
href="mailto:canderson@borregosolar.com" target="_blank"
moz-do-not-send="true">canderson@borregosolar.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Wrenches community,
<div><br>
</div>
<div>Hope folks are well out there. I am wondering if anyone
has experience addressing a frequency oscillation with a
split phase off grid Sunny Island system. I am working on
an off grid home project with 2 units that has just not
worked right since installation. The small number of 240
volt loads and most notably the geothermal heat pump goes
into a loud vibration as the frequency shifts and does so
for 20 seconds, then settles down into normal operation.
45 seconds later, it does it again and just repeats itself
until the water in the storage tank is up to temperature.
The current draw doubles when it is vibrating and it seems
to drain the batteries faster than expected when left on.</div>
<div><br>
</div>
<div>Wondering if anyone out there has any thoughts or is
experienced off grid tech in New England interested in
some troubleshooting work to help resolve things.</div>
<div><br>
</div>
<div>Please email me directly if possible at the following
address - <a href="mailto:canderson@borregosolar.com"
target="_blank" moz-do-not-send="true">canderson@borregosolar.com</a></div>
<div><br>
</div>
<div>Thanks and stay safe out there.</div>
<div>-- <br>
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