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    <p>Thanks Brad,</p>
    <p>I think I am finally getting it.</p>
    <p>When on-grid, the grid is providing wave form and transistors in
      BB are available to provide voltage regulation.</p>
    <p>When off-grid, the transistors in the BB are required to provided
      wave form and not available to provide regulation.</p>
    <p><br>
    </p>
    <div class="moz-cite-prefix">On 11/4/2019 6:10 AM, Bradley Bassett
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAEpjgH2PtPYYNb9uKE-y96+URKTh3RdV_paLdm2VHNvxfXC0Zg@mail.gmail.com">
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        <div>Mark,</div>
        <div><br>
        </div>
        <div>The difference is that when AC coupled the power is coming
          backwards into the AC out. When it's charging from the grid or
          generator it is charging from the AC inputs. The inverter can
          control the charge from the inputs but not what is coming in
          reverse into the output.</div>
        <div><br>
        </div>
        <div>Brad<br>
        </div>
      </div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">On Sun, Nov 3, 2019 at 6:10 PM
          Mark Frye &lt;<a href="mailto:markf@berkeleysolar.com"
            moz-do-not-send="true">markf@berkeleysolar.com</a>&gt;
          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">OK
          Jay that makes sense.<br>
          <br>
          This must mean that there is a significant difference in the
          function of <br>
          the BB inverter when it is in off-grid mode vs when it is in
          grid <br>
          connected mode.<br>
          <br>
          On 11/3/2019 5:45 PM, jay wrote:<br>
          &gt; No, older non frequency shift BB inverters don\u2019t
          communicate that way.<br>
          &gt;<br>
          &gt; They have no communication with a Rule 21 GT inverter.<br>
          &gt;<br>
          &gt; The BB, it will just keep charging and charging with any
          extra energy coming from the GT inverter.  The BB  has no
          regulation, there is no absorb or float, just charge.<br>
          &gt;<br>
          &gt; jay<br>
          &gt;<br>
          &gt; peltz power<br>
          &gt;<br>
          &gt;&gt; On Nov 3, 2019, at 4:31 PM, Mark Frye &lt;<a
            href="mailto:markf@berkeleysolar.com" target="_blank"
            moz-do-not-send="true">markf@berkeleysolar.com</a>&gt;
          wrote:<br>
          &gt;&gt;<br>
          &gt;&gt; OK, I am hearing this over and over and I just want
          to confirm that is true even if the BB is older and does not
          have "NEW Frequency Shifting AC Coupling".<br>
          &gt;&gt;<br>
          &gt;&gt; On 11/3/2019 4:26 PM, Dave Angelini Offgrid Solar
          wrote:<br>
          &gt;&gt;&gt; The BB inverter will drive the grid inverter off
          frequency because it is<br>
          &gt;&gt;&gt; full/floating and the grid tie will stop
          producing power. This is how AC<br>
          &gt;&gt;&gt; coupling works but if something goes wrong, like
          programming gets corrupted<br>
          &gt;&gt;&gt; by surges or the battery hits an LBCO or HBCO AC
          power will stop. Or if<br>
          &gt;&gt;&gt; this is being controlled by Soc and it gets wrong
          data or there is a<br>
          &gt;&gt;&gt; network issue, or all of the other things that
          can happen that I have not<br>
          &gt;&gt;&gt; thought of.<br>
          &gt;&gt;&gt;<br>
          &gt;&gt;&gt; Why do you not want to build a normal DC couples
          system? I forget<br>
          &gt;&gt;&gt; fast....Happy Hour!<br>
          &gt;&gt;&gt;<br>
          &gt;&gt;&gt; Dave Angelini Offgrid Solar<br>
          &gt;&gt;&gt; "we go where powerlines don't"<br>
          &gt;&gt;&gt; <a href="http://members.sti.net/offgridsolar/"
            rel="noreferrer" target="_blank" moz-do-not-send="true">http://members.sti.net/offgridsolar/</a><br>
          &gt;&gt;&gt; e-mail <a href="mailto:offgridsolar@sti.net"
            target="_blank" moz-do-not-send="true">offgridsolar@sti.net</a><br>
          &gt;&gt;&gt; text 209 813 0060<br>
          &gt;&gt;&gt;<br>
          &gt;&gt;&gt; On Sun, 3 Nov 2019 16:17:39 -0800, Mark Frye &lt;<a
            href="mailto:markf@berkeleysolar.com" target="_blank"
            moz-do-not-send="true">markf@berkeleysolar.com</a>&gt;<br>
          &gt;&gt;&gt; wrote:<br>
          &gt;&gt;&gt;&gt; Folks,<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; Please allow me to ask another question:<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; Suppose I have a bi-direction inverter/charge
          with no connection to the<br>
          &gt;&gt;&gt;&gt; grid.<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; I have GT inverter ac coupled and producing
          2000w. The battery is in<br>
          &gt;&gt;&gt;&gt; float, and I have 2000w of load connected.
          All is well.<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; Now suppose I remove the loads without
          disconnecting the GT inverters.<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; The word is that something bad happens now. I
          would like to understand<br>
          &gt;&gt;&gt;&gt; what that bad thing is.<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; I have one explanation that I think says that
          the GTs will continue to<br>
          &gt;&gt;&gt;&gt; produce the 2000w, and that energy will go
          into the batteries in an<br>
          &gt;&gt;&gt;&gt; unregulated fashion. When does this end, when
          the batteries blow up? Is<br>
          &gt;&gt;&gt;&gt; that the consequence of not disconnecting the
          GT?<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; With many thanks in advance for your help in
          understanding.<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt; Mark<br>
          &gt;&gt;&gt;&gt;<br>
          &gt;&gt;&gt;&gt;
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