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<DIV><FONT size=2 face=Calibri>The only way to really prevent that is to
disconnect everything but the solar array. Unfortunately, more than once we have
seen customers disconnect the array but leave other phantom loads on.
</FONT></DIV>
<DIV><FONT size=2 face=Calibri></FONT> </DIV>
<DIV><FONT size=2 face=Calibri>When most inverters shut down on LV they are
still drawing a few watts. And even with solar connected, if the voltage drops
too low, the charge controller often will not start back up until reset. I
suspect that could have happened in your case.</FONT></DIV>
<DIV><FONT size=2 face=Calibri></FONT> </DIV>
<DIV>..................................................................................................<BR>Northern
Arizona Wind & Sun - Electricity From The Sun Since 1979<BR>Solar Discussion
Forum: <A
href="http://www.wind-sun.com/ForumVB/">http://www.wind-sun.com/ForumVB/</A><BR>..................................................................................................</DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=solplex@montana.com href="mailto:solplex@montana.com">Solar
Plexus</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=re-wrenches@lists.re-wrenches.org
href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, December 20, 2009 4:22
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [RE-wrenches] low voltage
disconnect</DIV>
<DIV><BR></DIV>Wrenches.
<DIV><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>I have a
customer with a stand-alone system with an XW inverter, XW controller,
pole mounted array of four 235-watt panels, and 4 of the 8D gel
batteries. He uses the system mostly on weekends.
<BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>Winter came,
the solar array was still set at about 30°, a snowstorm covered
the panels while no one was there, and 4 days later the battery voltage
was 6.</DIV>
<DIV>The week-end use had been substantial, so I assume the batteries were low
prior to the snowstorm. With no solar coming in, and loads still on, the
battery voltage presumably went to Low Battery Cut Out voltage of 44
before the inverter disconnected the AC loads. With the AC loads
disconnected, and no DC loads in the system, <I>what caused the battery
voltage to go to 6</I>? </DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN> I assume
the XW controller used 2.5 watts continuous or 60 watt-hrs per day as battery
voltage went from 44 volts to 10 volts when the controller would have
shut off completely. <I>What happens with the inverter when the battery
goes below 44 volts? Does the inverter shut off and there is no more
draw on the batteries, or does the inverter continue to draw the no-load draw
of 28 watts, or does the inverter draw the search-load draw of 8 watts?
At what voltage does the inverter stop drawing
power? </I><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>At 44 volts,
the battery is presumed to be pretty dead. <I>How many amp-hours are available
in a 100 amp-hour 48v battery (4 12-v batteries in series) while drawing
the voltage from 44 volts and 6 volts? Is there anything there or
will the voltage just drop from 44 to 6 with very little power
draw?</I><BR></DIV>
<DIV><I><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN><SPAN
style="FONT-STYLE: normal" class=Apple-style-span>The Low Voltage Disconnect
is set for 44 volts, but if the inverter itself does not shut off, then
the practical low voltage becomes the voltage the inverter stops working at.
</SPAN>To protect the batteries, is there any advantage to limiting the
low voltage to 44 volts as opposed to 6 volts. If so, is there some way
to have the inverter shut itself off at low voltage?</I></DIV>
<DIV><I><BR></I></DIV>
<DIV>We have had this same thing happen with an Outback inverter, again taking
the batteries to near zero. <I> Is there any way that either the Outback
or Sunny Island would operate differently than described above?</I></DIV>
<DIV><BR></DIV>
<DIV>Looking forward to any comments on these issues. </DIV>
<DIV><BR></DIV>
<DIV>Thank you.</DIV>
<DIV><BR></DIV>
<DIV>Lee Tavenner</DIV>
<DIV>Solar Plexus</DIV>
<P>
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