<div dir="ltr"><div>AGMs are generally a lead calcium chemistry battery; lead calcium batteries are meant for a float service, which means they can sit in float for a long time without losing much capacity, but they can lose up to 10-15% when held in float for over 6 months, with the newer carbon additives that recoverd lost capacity comes back easier and faster than they did just 10 years ago. . Periodic cycling helps exercise the batteries and test the system, ensuring that when power goes out, the installer/user can verify it works as expected. <br><br>For FLA and AGMs, you should turn off the AC input breakers every 6 months and allow the inverter to switch to inverting mode for 2 to 4 hours. Monitor the DC voltage at each battery to ensure the individual battery voltages are falling uniformly, if six volt batteries they should fall withing .4 to .6 vdc of each other while 12v agm should be about .6 to .8vdc of each other. This is a quick test to ensure all cells are healthy and loading correctly. <br><br>After the (20-30%) discharge, put the system into bypass, loosen, clean (if necessary), and retorque your connections at all batteries, all the way back to the inverters. In a stationary application, these can loosen up over 9-12 months. In a mobile application, that's about 4-6 months... </div><div><br>After the connections, you can switch it back to normal mode and allow the chargers to recharge the battery bank to full capacity. </div><div><br></div><div>The most common issue with AGMs is chronic undercharging, which causes sulfation. This builds internal resistance in the battery and, over time, leads to cell heating and swelling. Please ensure the Bulk/Absorb V is set correctly for the full absorption timers with AGM. If you don't get the Absorb Timers long enough, you will quickly lose top-end capacity, usually within 2-3 months of operation. By the time it's discovered, the damage has already been done and is very difficult to recover. <br><br>There are many inverters and chargers on the market with pre-programmed "AGM" settings that are made up by some inverter/charger manufacturers and will quickly kill an AGM battery bank. Another issue is companies that rely solely on end amps (return amps or tail current) to determine whether an AGM battery is fully charged. Depending on the AGM, the battery is not fully charged until the current going into the battery falls below 2-4 % of the C20 rate for 60 mins... not the 0, 3, or 10 mins that many manufacturers are using today. Yes, some manufacturers will transition from ABSORB to float immediately once the charging current falls below 2%-4% of the C20 rate. That will kill any battery, and with LFP, it could cause massive balancing issues over time. <br><br>Maybe more than you wanted, but I hope this helps... <br><br><br></div><div><br></div><div><br></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><table style="width:490px;border-width:1px;margin:0px auto 0px 0px;height:155.5px" border="1"><colgroup><col style="width:123px"><col style="width:366px"></colgroup>
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<p> </p></div></div><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Dec 2, 2025 at 5:10 AM Mark Frye via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-4922574101520303017">
<div lang="EN-US" style="overflow-wrap: break-word;">
<div class="m_-4922574101520303017WordSection1">
<p class="MsoNormal">OK, I am thinking the most important thing is to ensure that the batteries are fully charged before I put them into storage.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"> RE-wrenches <<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>>
<b>On Behalf Of </b>James Jarvis via RE-wrenches<br>
<b>Sent:</b> Tuesday, December 2, 2025 4:41 AM<br>
<b>To:</b> RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>><br>
<b>Cc:</b> James Jarvis <<a href="mailto:jj@aprsworld.com" target="_blank">jj@aprsworld.com</a>><br>
<b>Subject:</b> Re: [RE-wrenches] AGMs - Maintenance Cycling<u></u><u></u></span></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">The life of the batteries will be longer in that service then in a deep cycling service.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<div>
<div>
<div>
<p class="MsoNormal">-James Jefferson Jarvis<br>
APRS World, LLC<br>
+1-507-454-2727<u></u><u></u></p>
</div>
<p class="MsoNormal"><a href="http://www.aprsworld.com/" target="_blank">http://www.aprsworld.com/</a><u></u><u></u></p>
</div>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">On Tue, Dec 2, 2025 at 6:30<span style="font-family:Arial,sans-serif"> </span>AM Mark Frye via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>> wrote:<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in">
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<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Thanks Guys,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">I guess I am wondering if the overall life of the battery will suffer if it is only ever cycled between 0 and 20% DOD and never deep cycled.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"> RE-wrenches <<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>>
<b>On Behalf Of </b>Jay via RE-wrenches<br>
<b>Sent:</b> Monday, December 1, 2025 3:31 PM<br>
<b>To:</b> RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>><br>
<b>Cc:</b> Jay <<a href="mailto:jay.peltz@gmail.com" target="_blank">jay.peltz@gmail.com</a>><br>
<b>Subject:</b> Re: [RE-wrenches] AGMs - Maintenance Cycling</span><u></u><u></u></p>
</div>
</div>
<p class="MsoNormal"> <u></u><u></u></p>
<div>
<p class="MsoNormal">Agreed and especially if the batteries are in a cooler to cold environment even less an issue as the colder temps slows down any self discharge <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">Jay<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12pt"> <u></u><u></u></p>
<blockquote style="margin-top:5pt;margin-bottom:5pt">
<p class="MsoNormal" style="margin-bottom:12pt">On Dec 1, 2025, at 12:57<span style="font-family:Arial,sans-serif"> </span>PM, James Jarvis via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>>
wrote:<u></u><u></u></p>
</blockquote>
</div>
<blockquote style="margin-top:5pt;margin-bottom:5pt">
<div>
<p class="MsoNormal"><span style="font-family:Tahoma,sans-serif"></span><u></u><u></u></p>
<div>
<div>
<p class="MsoNormal">Is there a specific problem you are trying to resolve? If the loads are shut off when in storage, I don't see any issue with not messing with any charging what-so-ever for some
months of storage.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">-James Jefferson Jarvis<u></u><u></u></p>
</div>
<div>
<div>
<div>
<div>
<p class="MsoNormal">APRS World, LLC<br>
+1-507-454-2727<u></u><u></u></p>
</div>
<p class="MsoNormal"><a href="http://www.aprsworld.com/" target="_blank">http://www.aprsworld.com/</a><u></u><u></u></p>
</div>
</div>
</div>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
<p class="MsoNormal"> <u></u><u></u></p>
<div>
<div>
<p class="MsoNormal">On Mon, Dec 1, 2025 at 10:47<span style="font-family:Arial,sans-serif"> </span>AM Mark Frye via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>>
wrote:<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt">
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<div>
<p class="MsoNormal">Folks,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">I have some AGMs that are PV charged during normal use and can be line charged when in storage (IOTA).<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">The batteries will generally see 10-20% daily DOD and will generally complete the absorb cycle and see a fair amount of float each day.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">They may be deployed in this mode for many months.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">After that, they will go into storage for several months.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Storage will include float charging at the IOTAs regular voltage.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">I have the LVD set at 46V.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Would it make sense to occasionally turn on the load, turn off the line charger, let the bank run down to LVD, turn off the load, turn on the charger with the increased voltage
jumper installed, charge overnight, remove jumper and resume normal float charging?<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Thanks,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Mark<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
</div>
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