<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hi Steve,<div><br></div><div>Maybe you can elaborate as to how this could happen.</div><div><br></div><div>Let’s say all the batteries are designed for a 57.4 usual charge voltage with an acceptance range of around 56-58.4v. </div><div><br></div><div>If you’re charging 10 batteries to 57.4v, the most that any one battery gets to is 57.4. If one gets full before others then it stops accepting charge, but at no point in the system does any battery see more than 57.4. </div><div><br></div><div>Iv’e seen this with same 10 batteries all from one OEM all in one system, all new. They get off just a little and some take longer or shorter to charge fully to 100% but the voltage never rises above what the inverter or CC is set to. I don’t understand how this would cause damage or issue.</div><div><br></div><div><br></div><div><br></div><div>thanks</div><div><br></div><div>jay</div><div><br></div><div><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Jul 14, 2025, at 7:46 AM, Steve Higgins via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:</div><br class="Apple-interchange-newline"><div><div dir="ltr"><div>I wouldn't do it... By doing so, you'll likely void any manufacturer's warranty. </div><div><br></div><div>If you must do it, I would manually balance the old/new banks every 60-90 days. This involves separating the parallel strings of batteries and charging each string independently to achieve a full charge. If you don't do this, the different ages can cause imbalances, which will lead to problems with the BMS, regardless of whether it is in open-loop or closed-loop configuration. </div><div><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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<div style="text-align:left"><span style="color:rgb(216,0,29);font-family:arial,helvetica,sans-serif;font-size:8pt"><strong>Steve Higgins</strong> <span style=""><strong>⋅</strong></span> <span style=""><strong>Technical Services Manager</strong></span></span></div>
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</table><div> <br class="webkit-block-placeholder"></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Jul 14, 2025 at 4:09 AM Jason Szumlanski via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">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 dir="auto"><div>There are never-ending videos on YouTube showing different brands and capacities of LFP batteries working in parallel. I have never tried it myself, and every instinct says don't do it, but I have a situation where it would be very helpful. </div><div dir="auto"><br></div><div dir="auto">I have a client with an older 60 kWh battery that is discontinued and incompatible with any other battery from the same manufacturer. It has a BMS with a 51.2 volt nominal rating. They need another 20 kWh of capacity. It is too costly to scrap the existing battery and start over, and the existing battery has been tested and confirmed to hold very close to its rated capacity.</div><div dir="auto"><br></div><div dir="auto">What is the real deal on mixing and matching? Is anyone doing this safely and successfully? I wonder what the battery manufacturers say about it. </div><div dir="auto"><br></div><div dir="auto">Jason Szumlanski </div><div dir="auto">Florida Solar Design Group </div><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><b><div style="text-align:center"><table border="0" cellpadding="0" cellspacing="0" style="color:rgb(34,34,34);font-weight:400;text-align:start;font-family:"helvetica neue",helvetica,arial,sans-serif"><tbody></tbody></table></div></b></div></div></div></div></div></div></div></div>
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