<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:blue;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:Consolas;
color:black;}
span.il
{mso-style-name:il;}
span.EmailStyle20
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:black;}
span.EmailStyle21
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body bgcolor=white lang=EN-US link=blue vlink=blue>
<div class=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Bob,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The power draw of a system with a 4kW inverter powering a 26W
load will just be 26W plus the tare loss of the inverter. The inverter will be
damn close to 100% efficient at that load. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Inverter efficiency charts are a bit confusing at the low end.
All of them will show efficiencies of under 50% at the low end, but that is
just the effect of the inverter’s tare losses. For instance, if the
inverter draws 20W at full voltage idle (no load, but not sleeping) and you run
a 20W load, then you are operating at 40W draw from the battery. This shows up
as 50% efficiency on the chart, but in fact, you are only using 20W to power
that 20W load (alright…maybe 21W)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The Magnum MS4024-AE has a no load draw of 25W (according to the
spec sheet), so with the 26W load, you will draw about 51W, or about 2A from a
24V battery sitting at 25VDC. If you figure a 12hr night, that’s 612
Whrs, or about 25AH from the battery. This is quite a bit of power, and if you
were in a sunnier area, it would certainly make sense to just add PV. Where you
are, it might be more iffy, but I still think that you are better off just
adding to the PV array.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Brian Teitelbaum<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>AEE Solar<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>bob<br>
<b>Sent:</b> Wednesday, May 12, 2010 3:29 AM<br>
<b>To:</b> Allan@positiveenergysolar.com; 'RE-wrenches'<br>
<b>Subject:</b> Re: [RE-wrenches] Tiny load problem<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>48
volts is a consideration and I have done many, but the problem is still the 26
AC watt load and the inverters efficiency at that light a load. Just hate to
burn that much DC to generate that little AC. I am unsure if it is better at 48
volts or not.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Maybe
I should not sweat it but it just bugs me. It probably comes from years of
looking at “E meters” and playing with loads. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Bob<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Allan
Sindelar<br>
<b>Sent:</b> Wednesday, May 12, 2010 2:09 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Tiny load problem<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Bob,<br>
If I step back and look at your question, another bigger question comes up: if
you are designing a system with two inverters in order to double charging
current, you must have a pretty good sized battery bank. In general, I would
suggest that you look at a 48V system, rather than 24V, once it gets to that
size. Equivalent charging rate, but smaller wire, lower component amperage
requirements and fewer battery strings to get the capacity you're apparently
looking for.<o:p></o:p></p>
<div>
<p class=MsoNormal><span class=il><b>Allan</b></span><b> Sindelar</b><span
style='font-size:10.0pt'><br>
<a href="mailto:Allan@positiveenergysolar.com" target="_blank"><span class=il><u>Allan</u></span><u>@positiveenergysolar.com</u></a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b>Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank"><u>www.positiveenergysolar.com</u></a></span><o:p></o:p></p>
</div>
<p class=MsoNormal><br>
<br>
Phil Undercuffler wrote: <o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>If the normal connected loads
are within the capacity of a single inverter (which may actually be possible --
I run my whole house off one Outback FX2024, microwave, dishwasher, washing
machine and all) then you can just leave one of the inverters in sleep mode or
disable output but leave input/charging enabled. <br>
<br>
Which inverters are you planning on using for the generator charging?
Depending upon which brand or how sophisticated you want to be, there are a
couple ways to skin this cat. Easiest and cheapest is to simply not
connect up any AC output wiring or stacking cables to the second inverter, and
program it to stay asleep and charge only when it sees AC input power. <br>
<br>
I used to be religious about making sure my inverter was asleep, and even had a
second baby inverter to power a handful of full time or sensitive loads.
However, it got difficult trying to explain why you couldn't just plug the
vacuum cleaner into just-any-old-outlet, and as my electronic widget count
expanded it became less and less advantageous to have that baby inverter.<br>
<br clear=all>
Phil Undercuffler<br>
Conergy<br>
<br>
<br>
<br>
<o:p></o:p></p>
<div>
<p class=MsoNormal>On Tue, May 11, 2010 at 9:58 AM, bob <<a
href="mailto:reellison@gmail.com"><u>reellison@gmail.com</u></a>> wrote:<o:p></o:p></p>
<div>
<div>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>I
am sizing a system that will have dual inverters to shorten generator charging
in the winter and enough solar to charge the rest of the time. </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Here’s
the problem, the inverter will not be able to get into sleep mode at night.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'> </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>There
are 2 cell chargers and a “cpap” machine having to run all night.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>It
only totals 26 watts, has anyone found a better way to do this without having
to keep an inverter awake to produce 26 watts?</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>I
would like to dedicate a Morningstar 300 watt inverter for the job but the
system is 24 volts and Morningstar has no plans to make one in 24 volts.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'> </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Anyone
got any other ideas, or am I best to just deal with it?</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'> </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Thanks,</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:14.0pt;font-family:"Calibri","sans-serif"'>Bob</span><o:p></o:p></p>
</div>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org"><u>RE-wrenches@lists.re-wrenches.org</u></a><br>
<br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"
target="_blank"><u>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</u></a><br>
<br>
List-Archive: <a
href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org"
target="_blank"><u>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</u></a><br>
<br>
List rules & etiquette:<br>
<a href="http://www.re-wrenches.org/etiquette.htm" target="_blank"><u>www.re-wrenches.org/etiquette.htm</u></a><br>
<br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org" target="_blank"><u>www.members.re-wrenches.org</u></a><o:p></o:p></p>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p>
<pre><o:p> </o:p></pre><pre style='text-align:center'><o:p> </o:p></pre><pre
style='text-align:center'><o:p> </o:p></pre><pre style='text-align:center'>
<hr size=4 width="90%" align=center>
</pre><pre style='text-align:center'><o:p> </o:p></pre><pre
style='text-align:center'><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>_______________________________________________<o:p></o:p></pre><pre>List sponsored by Home Power magazine<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List Address: <a
href="mailto:RE-wrenches@lists.re-wrenches.org"><u>RE-wrenches@lists.re-wrenches.org</u></a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Options & settings:<o:p></o:p></pre><pre><a
href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"><u>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</u></a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List-Archive: <a
href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org"><u>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</u></a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List rules & etiquette:<o:p></o:p></pre><pre><a
href="http://www.re-wrenches.org/etiquette.htm"><u>www.re-wrenches.org/etiquette.htm</u></a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Check out participant bios:<o:p></o:p></pre><pre><a
href="http://www.members.re-wrenches.org"><u>www.members.re-wrenches.org</u></a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre> <o:p></o:p></pre></div>
</body>
</html>