The key thing to remember, due to this high impedance, is that any attempt to charge them in series will end up with almost ALL the voltage across the single cell with the highest internal resistance and then it gets all the energy and ... Big problem! Bob
-----Original Message----- From: EV <[email protected]> On Behalf Of Haudy Kazemi via EV Sent: Tuesday, March 19, 2019 10:57 AM To: Electric Vehicle Discussion List <[email protected]> Cc: Haudy Kazemi <[email protected]> Subject: Re: [EVDL] NMC cells ran below 2.5 vots n left Here is an article has some info on restoring LiPo cells. Batteries tend to exhibit increased internal resistance as voltages fall. The article empasizes that restoration doesn't mean the cells will be like new. They may have lost capacity and may have increased self discharge rates, but may also be useable again. Do the charging in a fire safe area. In short, charge the cells very slowly (suggested 1/20 to 1/10 C rate) and monitor them continuously for bloating or heat buildup, at least until they get back into normal voltage ranges. At normal voltages, a standard lithium charger should work, just keep the C rates low while charge levels come back up. Once charged, you'll be able to assess damage by doing capacity and discharge rate checks. This data is useful for identifying acceptable future charging C rates as cell characteristics may have changed from their original values. https://www.electricrcaircraftguy.com/2014/10/restoring-over-discharged-Li Pos.html On Tue, Mar 19, 2019, 02:28 ken via EV <[email protected]> wrote: > I bought a pack or lihium ion of cells and they arived pretty much dead. > like 0 or .25 each cell. > > I used 306b nicad setting to bring them up to 3.00, then swtiched to > lipo to charge to 3.70 . > > someone told me that charging theses cells could be dangerous, because > the dendrits could lead dangerous overheating. theses battery i think > where used for like a bus or something. theses are from > > > https://www.techdirectclub.com/johnson-controls-24-cells-solar-battery > -90-vdc-total-2-5-kwh/ > > theses cells can do 10c so i'm rather concrned. I wish I knew that > manufacuter or specs or more about the cells property. > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20190319/1d44e5 18/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
