Hi Steve, Maybe you can elaborate as to how this could happen.
Let’s say all the batteries are designed for a 57.4 usual charge voltage with an acceptance range of around 56-58.4v. 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. 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. thanks jay > On Jul 14, 2025, at 7:46 AM, Steve Higgins via RE-wrenches > <[email protected]> wrote: > > I wouldn't do it... By doing so, you'll likely void any manufacturer's > warranty. > > 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. > > > > > Steve Higgins ⋅ Technical Services Manager > t +1.902.597.4020 m +1.206.790.5840 > f +1.902.597.8447 e [email protected] <mailto:[email protected]> > > CONFIDENTIALITY: The information transmitted herein is intended only for the > addressee and may contain confidential, proprietary and/or privileged > material. Any unauthorized review, distribution or other use of or the taking > of any action in reliance upon this information is prohibited. If you receive > this email in error, please contact the sender and delete or destroy this > message and all copies. > > > > On Mon, Jul 14, 2025 at 4:09 AM Jason Szumlanski via RE-wrenches > <[email protected] > <mailto:[email protected]>> wrote: >> 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. >> >> 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. >> >> 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. >> >> Jason Szumlanski >> Florida Solar Design Group >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> <http://re-wrenches.org/> >> >> List Address: [email protected] >> <mailto:[email protected]> >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/[email protected]/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org <http://www.members.re-wrenches.org/> >> > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org >
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