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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dan,<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'>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?<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'>I run into this once in a while, so this piece of information would help me make some better decisions.<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'>Thanks,<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-family:"Calibri","sans-serif";color:#1F497D'>Jason Szumlanski<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Fafco Solar</span><span style='font-size:4.0pt;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'><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 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"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> re-wrenches-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Exeltech<br><b>Sent:</b> Thursday, September 01, 2011 3:58 PM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] unique battery bank design question<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td valign=top style='padding:0in 0in 0in 0in'><p class=MsoNormal>Mac,<br><br>Don't tap the battery. Bad idea. Uneven loading = unequal charge/discharge, which leads to shortened battery life and other troubles.<br><br>Better idea: If you know the maximum load current, use high-efficiency DC-DC supplies of adequate current and other ratings to step 48V down to 12 or 24V.<br><br><br>Dan<br>Sr. Engineer<br>Exeltech<br><br><br>--- On <b>Thu, 9/1/11, mac Lewis <i><maclewis1@gmail.com></i></b> wrote:<o:p></o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'><br>From: mac Lewis <maclewis1@gmail.com><br>Subject: [RE-wrenches] unique battery bank design question<br>To: RE-wrenches@lists.re-wrenches.org<br>Date: Thursday, September 1, 2011, 2:52 PM<o:p></o:p></p><div id=yiv498420474><p class=MsoNormal>Hello wrenches,<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I have a battery bank questions. I have an Oil & Gas client interested in setting up an off-grid control system that has a various DC loads at 12VDC, 24 VDC and 48 VDC. My thought is to build a 48 V battery bank and tap off the bank at various points to create a 12V bus, 24V bus and 48V bus. I am a bit concerned about unequal loading of the batteries. Has anyone dealt with something like this that would like to share some insight?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Thanks<br clear=all><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>-- <o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal>Mac Lewis<o:p></o:p></p></div></div></td></tr></table><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p></div></body></html>