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    On 1/4/2012 3:01 PM, All Solar, Inc. wrote:
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      <div><font face="Arial" size="2">Wrenches,</font></div>
      <div><font face="Arial" size="2">Once again I am trying to size a
          grid tie w/battery system and I struggle a little with the
          efficiencies of them.</font></div>
      <div><font face="Arial" size="2">With PV Watts (v.1), is changing
          the DC to AC derate an accurate method for getting the output?</font></div>
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      <div><font face="Arial" size="2">Thanks in advance!</font></div>
      <div> </div>
      <div><font face="Arial" size="2">Jeremy</font></div>
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    <br>
    <br>
    If you keep the batteries charged  to a voltage just above their
    resting voltage,<br>
    say, 52 volts for a 48V system, and the battery bank isn't too
    large, (~225 A-hours,<br>
    maybe a bit more), about 90%  PV to grid AC efficiency is in the
    ball park.<br>
    <br>
    That's what we figured in the early days of GFX inverters at OB. 
    That's giving<br>
    5% for the electronics and 5% for keeping up the batteries.<br>
    Different and/or more accurate information may have come along since<br>
    that time.<br>
    <br>
    boB<br>
    <br>
    <br>
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    <br>
    <br>
    <br>
    <br>
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      <div><font face="Arial" size="2">  </font></div>
      <div><font face="Arial" size="2">All Solar Inc.<br>
          Jeremy and Amy Rodriguez<br>
          1463 M St<br>
          Penrose, CO 81240<br>
          <a moz-do-not-send="true" href="http://www.asolarelectric.com">www.asolarelectric.com</a><br>
          Phone 719-372-3808<br>
          Fax 719-372-3804<br>
          Email <a moz-do-not-send="true"
            href="mailto:allsolar@scswifi.net">allsolar@scswifi.net</a><br>
          Email <a moz-do-not-send="true"
            href="mailto:allsolar@live.com">allsolar@live.com</a></font></div>
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      <pre wrap="">_______________________________________________
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