<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr">One question I have for those more versed than me in lithium is, I\u2019m under the impression that having a lithium battery in float for years isn\u2019t good for it. Or at the very least it has to be cycled with some regularity. </div><div dir="ltr"><br></div><div dir="ltr">I\u2019d like to hear data on that</div><div dir="ltr"><br></div><div dir="ltr">Thx</div><div dir="ltr">Jay</div><div dir="ltr"><br></div><div dir="ltr">Peltz power. </div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"><br><blockquote type="cite">On May 23, 2020, at 10:08 PM, Ray <ray@solarray.com> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">\ufeff
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<p>I suggest starting with a very simple look at the continuous
output rating of the battery and match that to the inverter
continuous rating. This ends up with quite a bit more battery than
you might think at first. However, if the customer paid the big
bucks for a battery backup system, they should at least get enough
battery to operate the inverter at its rated power. Anything
less, I would consider poor design. The same goes for lead acid
batteries, they just don't work well, even on grid, when the
battery is undersized. Even lead acid batteries have maximum
current output ratings that should at least be matched to the
inverter rating. <br>
</p>
<p>If you WERE going to under size the battery, then you should keep
it safe by reducing the size of the inverter battery breaker as
well. I know this "micro battery for GTB" is becoming a trend,
but it doesn't mean its right. <br>
</p>
<pre class="moz-signature" cols="72">Ray Walters
Remote Solar
303 505-8760</pre>
<div class="moz-cite-prefix">On 5/23/20 5:48 PM, Mick Abraham wrote:<br>
</div>
<blockquote type="cite" cite="mid:CABOJ=XRzShwOfrt=ptx34r2AmuDOZOx6uN54Qji=ED-+Eo8WBQ@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Greetings, All~ Mark Frye had asked: "...with a
4000w Outback Radian, AC coupled with 2000w of PV, what is the
smallest Li battery I would want for stable operation?"
<div><br>
</div>
<div>Mick's reply: In the lithium arena, one often finds the
ratings in kilowatt-hours rather than in amp-hours. This is an
easy conversion for us energy nerds to make, so below I'm
mainly using watts & watt-hours with occasional
conversions to amp-hours.</div>
<div><br>
</div>
<div>I suggest that you start with the spec sheet (of whichever
brand lithium battery is on your radar), & see what the
manufacturer says about "allowable rate of recharge". You may
find that C/2 is an acceptable rate with several
manufacturers, Mark--much faster than what we're accustomed to
with typical lead-acid batteries. Let's assume:</div>
<div><br>
</div>
<div>* ...that your AC coupled PV array crests around 1800 watts
to the battery when there are no loads</div>
<div>* ...that the battery is below 100% state of charge, and</div>
<div>* ...that the solar conditions are optimal. </div>
<div><br>
</div>
<div>Let's further assume that those conditions represent your
battery's highest energy rate in either direction. </div>
<div><br>
</div>
<div>1800w X two hours = 3,600 watt-hours dividing by 48v
nominal = 75 amp-hours in the above hypothetical situation. </div>
<div><br>
</div>
<div>++++++++++++++++++++++++++++++</div>
<div><br>
</div>
<div>
The rate at which a battery can receive energy is (usually)
also the rate at which it can comfortably deplete, so let's
briefly look at the flip side: Assuming the battery mfr. wants
the watt-hours to be no less than two times the maximum
wattage, a 3600 watt-hour (C/2) battery should not be depleted
faster than 1800 watts. Your 4kW Radian, Mark, could exceed
that if the loads demand it--& maybe your loads don't.
Motor starting surges should probably be part of the thinking
& it wouldn't hurt to ask the mfr.'s opinion about short
term surges which briefly deplete the battery faster than the
hypothetical two hour rate.</div>
<div><br>
</div>
<div>By approaching this question based on the battery
manufacturer do's & don'ts, one improves the chance of
getting warranty coverage should it later be needed. "What the
large print giveth, the fine print taketh away." </div>
<div><br>
</div>
<div>The Wrench List is the Bomb! </div>
<div><br clear="all">
<div>
<div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">
<div>Mick Abraham, Proprietor<br>
<a href="http://www.abrahamsolar.com" target="_blank" moz-do-not-send="true">www.abrahamsolar.com</a><br>
<br>
Landline: 970-731-4675</div>
<div>Cell phone or for text messaging: 970-946-6584</div>
</div>
</div>
</div>
</div>
</div>
<div hspace="streak-pt-mark" style="max-height:1px"><img alt="" style="width:0px;max-height:0px;overflow:hidden" src="https://mailfoogae.appspot.com/t?sender=abWlja0BhYnJhaGFtc29sYXIuY29t&type=zerocontent&guid=74c54196-b300-4b9d-8f4a-9fa513751306" moz-do-not-send="true" data-unique-identifier=""><font size="1" color="#ffffff">\u1427</font></div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
List sponsored by Redwood Alliance
List Address: <a class="moz-txt-link-abbreviated" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a>
Change listserver email address & settings:
<a class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a>
List-Archive: <a class="moz-txt-link-freetext" href="http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html">http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html</a>
List rules & etiquette:
<a class="moz-txt-link-abbreviated" href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a>
Check out or update participant bios:
<a class="moz-txt-link-abbreviated" href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a>
</pre>
</blockquote>
<span>_______________________________________________</span><br><span>List sponsored by Redwood Alliance</span><br><span></span><br><span>List Address: RE-wrenches@lists.re-wrenches.org</span><br><span></span><br><span>Change listserver email address & settings:</span><br><span>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</span><br><span></span><br><span>List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html</span><br><span></span><br><span>List rules & etiquette:</span><br><span>www.re-wrenches.org/etiquette.htm</span><br><span></span><br><span>Check out or update participant bios:</span><br><span>www.members.re-wrenches.org</span><br><span></span><br></div></blockquote></body></html>