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 < ev@lists.evdl.org> 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 michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150528/278569ff/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)
