<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">At the risk of sounding sarcastic (and I assure this is not my intent) .. to allow a DC appliance to wait and simply turn on when when necessary and not waste power when it is off would take a battery .. internal or external to the appliance.<br><br>Something has to keep the appliance powered. The best we can do is minimize the idle power consumption.<br><br>"Super capacitors" can provide some degree of backup for very low-power needs (micro-watts), but they too will go dead over time if not used, or when given a long-term power draw without being recharged (sounds like a battery again .. no?).<br><br>Dan<br><br><br>--- On <b>Thu, 9/1/11, Darryl Thayer <i><daryl_solar@yahoo.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Darryl Thayer
<daryl_solar@yahoo.com><br>Subject: Re: [RE-wrenches] unique battery bank design question<br>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>Date: Thursday, September 1, 2011, 5:01 PM<br><br><div id="yiv803988760"><div style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255); font-family: arial,helvetica,sans-serif; font-size: 12pt;"><div style=""><span style="">I am both interested in the idle power, and the operating efficiency<br style="" class="yiv803988760yui-cursor"></span></div>
<div style="">This often comes up, but what does it require to allow a DC appliance to wait and simply turn on when when necessary and not waste power when it is off? </div>
<div style="">Darryl<var id="yiv803988760yui-ie-cursor"></var><br style=""></div>
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<div style="border: 1px solid rgb(204, 204, 204); padding: 0px; line-height: 0pt; margin: 5px 0px; height: 0px; font-size: 0px;" class="yiv803988760hr"></div><b><span style="font-weight: bold;">From:</span></b> Exeltech <exeltech@yahoo.com><br><b><span style="font-weight: bold;">To:</span></b> RE-wrenches <re-wrenches@lists.re-wrenches.org><br><b><span style="font-weight: bold;">Sent:</span></b> Thursday, September 1, 2011 3:30 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [RE-wrenches] unique battery bank design question<br></font>
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<td valign="top">Hi Jason,<br><br>Well designed off-the-shelf converters can achieve 90% efficiency, and as you mention, this will vary a bit depending on the rated output current of the converter vs. the actual load current.<br><br>I've designed and built 24V @ 25A to 12V @ 50A converters for my own use that are in the 95% realm.<br><br>Your mileage may vary.<br><br>Dan<br><br><br>--- On <b>Thu, 9/1/11, Jason Szumlanski <i><Jason@fafcosolar.com></i></b> wrote:<br>
<blockquote style="border-left: 2px solid rgb(16, 16, 255); padding-left: 5px; margin-left: 5px;"><br>From: Jason Szumlanski <Jason@fafcosolar.com><br>Subject: Re: [RE-wrenches] unique battery bank design question<br>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>Date: Thursday, September 1, 2011, 3:07 PM<br><br>
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<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;">Dan,</span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;"> </span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;">What kind of efficiency level (%) can you get out of a DC-DC supply on a small load, say <5A @ 12V with a 48V->12V converter? Is the efficiency level highly variable depending on load as a percentage of the converter’s maximum capacity, or is it pretty constant?</span></div>
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<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;">I run into this once in a while, so this piece of information would help me make some better decisions.</span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;"> </span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;">Thanks,</span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;"> </span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125);">Jason Szumlanski</span></div>
<div class="yiv803988760MsoNormal"><span style="color: rgb(31, 73, 125); font-size: 11pt;">Fafco Solar</span><span style="color: rgb(31, 73, 125); font-size: 4pt;"> </span></div>
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