<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">William,<div><br></div><div>This is one reason I choose to avoid the "black box" approach to Li-ion batteries for our customers. There are several companies offering enclosed battery/controls like the OES. Their approach does not match well to the off-grid and mobile markets that I serve. </div><div><br></div><div>Since most LFP batteries can handle 10C for up to 30 seconds (Winston LFP can surge to 20C!) and 2C-3C continuous discharge, it makes sense to me to design a protection system that can't utilize that capability. Our LFMP battery has an external CPU that I can program. We also use external high current relays for the protective circuits so the full load of the inverter can be put to use.</div><div><br></div><div>With a LFP battery bank of 48 volts and 400AH, somewhat small for off grid, the battery can operate continuously at 1200 amps or about 60kW output and surge to 4000 amps/600kW. This obviously is way beyond the demand capability of the inverter(s). A quick look at the SI6048 data sheet shows maximum AC current is 11kW for 3 seconds.</div><div><br></div><div>I am glad you noticed the extremely low voltage sag under load. This feature means lower current which should translate to longer life for inverters. It also means starting loads that you can’t with a similar sized lead acid battery. A 1C load typically has only 0.2 volt sag. For 48 volt systems, this means maintaining 51.2 volts throughout the full battery use. In fact, a 1C load will still only have 0.2 volt drop until about 90% discharged. Simply amazing.</div><div><br></div><div>Larry Crutcher</div><div><br>
<br><div><div>On Sep 17, 2014, at 10:15 PM, William Miller <<a href="mailto:william@millersolar.com">william@millersolar.com</a>> wrote:</div><br class="Apple-interchange-newline"><div><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"><meta name="Generator" content="Microsoft Word 14 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
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</o:shapelayout></xml><![endif]--><div lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D">Larry:<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D"> </span></p><p class="MsoNormal"><font face="Arial, sans-serif"><font color="#1f497d">…</font><font color="#1f497d" size="3">...</font></font><span style="color: rgb(31, 73, 125); font-family: Arial, sans-serif; font-size: 12pt;">The internal battery management system will allow them to disconnect under surge loads, just when you need your batteries to stay connected. I will be conversing with the manufacturer to learn more about them.</span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D"> </span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D">William<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D"> </span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1F497D"> </span></p></div></div></div></div></div></body></html>