<div dir="auto">Zeke:</div><div dir="auto"><br></div><div dir="auto">This sounds like a classic case of the BMS increasing impedance at high SOC and the charge controller not responding fast enough. </div><div dir="auto"><br></div><div dir="auto">If true, your solution is dialing down the absorb voltage until this stops happening. You then do not get full charge. </div><div dir="auto"><br></div><div dir="auto">Then comes the risk of the BMS units not calibrating. </div><div dir="auto"><br></div><div dir="auto">Sorry to be a Debby Downer but I am still traumatized trying to i<span style="font-family:-apple-system,sans-serif">ntegrate lithium batteries into a Sunny Island system. </span></div><div dir="auto"><span style="font-family:-apple-system,sans-serif"><br></span></div><div dir="auto"><span style="font-family:-apple-system,sans-serif">I do not recommend connecting old school inverters to lithium batteries. </span></div><div dir="auto"><br clear="all"><div dir="auto"><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><br>William Miller<br>Miller Solar.com<br>805-438-5600<br><a href="http://www.millersolar.com">www.millersolar.com</a><br></div></div></div><div><br></div><div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Sun, Mar 15, 2026 at 3:32\u202fPM Zeke Yewdall 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>I've got a system that is throwing occasional battery voltage sensor errors and shutting down, then turning back on when the error clears a few seconds to a minute later. Stacked system, two VFX3524's, two FM60's, 600AH of LFP batteries (EG4 LL rackmounts) in open loop. It tends to do this when the batteries are full with lots of sun out.</div><div><br></div><div>I am not 100% sure that the batteries are happy -- it's possible that the BMS's are shutting off charging, and that's causing a spike in the bus voltage the inverters are seeing. But if that's so, I don't see anything recording it. Charge controllers both report 28.2 volts as highest voltage for the day. I adjusted the absorb voltage and time down a little bit -- we had set it up a few months ago at 28.2 for 2 hours to try to get the batteries to balance better, but I took it down to 28.0 for 1 hour now. Float was at 27.1, I reduced it to 27.0.</div><div><br></div><div>But, could this be an actual problem with the inverters? Or likely still a programming issue?</div><div><br></div><div>Z</div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr">Zeke Yewdall<div>PV Engineer</div><div>NABCEP #031508-89</div><div><a href="mailto:zeke@darkforestsolar.com" target="_blank">zeke@darkforestsolar.com</a></div><div>303-523-3592</div></div></div></div></div></div>
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