I agree with Cor's comment on charging versus resting voltage - I mean a cutoff voltage to be the "resting voltage."
On Thu, May 28, 2015 at 2:18 PM, Michael Ross <[email protected]> wrote: > I don't know of a lithium cell that would be carrying significant capacity > at 2 Volts. That voltage would not hurt a Li cell. 2V would be a reasonable > low cut off. Higher gives you more leeway if your are far out of bottom > balance. If you bottom balance to begin with you are safer for a longer > time. A DIY'er can bottom balance, but a pack manufacturer has to devote > more time than they are willing to top balancing. > > The Batt Bridge would warn you if one cell has gone off the reservation. > Not which one, but you would know in which half pack and then you check the > individual cells. > > The high cutoff is different depending on the chemistry of the positive > electrode. It is very important to get this right because fully charging > cells in conjunction with high temperatures the situation that is damaging > to Li cells. A chemistry like LiFePO4 has a lower voltage/capacity curve > than most other cell chemistries. 3.4V max might be all you want for max > voltage on a LiFePO4 system (CALB, others). Other chemistries would be > safe at 3.4V or less, but some would not be charging very well at that low > voltage. > > This the upper cut off situation is when you want to know exactly what you > are dealing with - and this is probably a hard thing to sort out with > uncertain supplier chains you <-- importer <-- exporter <-- Chinese factory > for example. > > Mike > > > On Thu, May 28, 2015 at 2:02 PM, EVDL Administrator via EV < > [email protected]> wrote: > >> On 28 May 2015 at 10:18, damon henry via EV wrote: >> >> > There are a couple of fairly simple solutions to that particular >> > problem. First, a charger that is set at a low enough voltage to limit >> > that danger. >> >> I'm not a lithium expert, but this sounds like it should work well as long >> as your cells remain balanced. If some are different temperatures, >> differing efficiency could get them out of balance. >> >> I would think you'd also need some kind of over-discharge protection. I >> wonder if that could be something as simple as a Lee Hart "batt-bridge" >> imbalance alarm. >> >> http://www.evdl.org/pages/battbridge.html >> >> Do lithium cells have enough voltage falloff when flat to make it work as >> needed here? >> >> Sorry about the bike/truck confusion. That one flew right past me. :-\ >> >> David Roden - Akron, Ohio, USA >> EVDL Administrator >> >> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >> EVDL Information: http://www.evdl.org/help/ >> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >> Note: mail sent to "evpost" and "etpost" addresses will not >> reach me. To send a private message, please obtain my >> email address from the webpage http://www.evdl.org/help/ . >> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >> >> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> For EV drag racing discussion, please use NEDRA ( >> http://groups.yahoo.com/group/NEDRA) >> >> > > > -- > To invent, you need a good imagination and a pile of junk. > Thomas A. Edison > <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> > > A public-opinion poll is no substitute for thought. > *Warren Buffet* > > Michael E. Ross > (919) 585-6737 Land > (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google > Phone > (919) 631-1451 Cell > > [email protected] > <[email protected]> > > > -- To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 585-6737 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150528/b55f62bd/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
