Sounds possible. My thoughts: Unfortunately, voltage is not a great way to evaluate cells, but that sounds good FWIW. Is your meter really reliable, and accurate to measure ±0.001 volts? under conditions of different temperature? Is the accuracy reall somewhat less good than ±0.001V? Recently calibrated? It is such a small amount that noise may be what you have read. The first time you read them was that 3.3V? Or 3.300V? Different meters used? To me 3.3V possibly means ±0.1V.
One of the last things Dahn says in his lecture is essentially - want your cells to last a long time? Put them in the refrigerator very chance you get. Hard to do h an EV pack. Temperature is the enemy, and especially with LFP. Where were they stored for 16 months? It really becomes and important question when people are claiming a cell lasted or degraded of such and such a period of time. Also the SOC% which is hard to know without a full cycle and Ah measurement. That is really the topic change in amount of stored charge, not voltage changes. LFP particularly sees a lot of change in charge for little change in voltage. On Thu, Jun 25, 2015 at 6:24 PM, Paul Dove via EV <ev@lists.evdl.org> wrote: > Here's my observation I received my cells and new the measured 3.3 volts. > 16 months later when I put then in the vehicle they measured 3.298 and > 3.297. > > Sent from my iPad > > > On Jun 20, 2015, at 12:39 PM, Cor van de Water via EV <ev@lists.evdl.org> > wrote: > > > > One last question and then I prefer not to extend this subject any > longer since it appears beaten to death: > > > > > > > > Paul and Michael, > > > > Did you guys actually *measure* Li-Ion cells over extended period to > verify if they show self-discharge or not? > > > > Because the interesting thing is that self-discharge is not only well > defined (so it must be an issue) but it appears > > > > that everyone who measured Li-Ion cells over extended time periods (and > not just a quick voltage check that they still had juice) > > > > is convinced that they do show self-discharge. > > > > To me, it seems to be the classical case of “in theory, there should be > no difference between practice and theory. In practice, however…”. > > > > > > > > Regards, > > > > > > > > Cor van de Water > > > > Chief Scientist > > > > Proxim Wireless > > > > > > > > office +1 408 383 7626 Skype: cor_van_de_water > > > > XoIP +31 87 784 1130 private: cvandewater.info < > http://www.cvandewater.info> > > > > www.proxim.com <http://www.proxim.com/> > > > > > > > > > > > > This email message (including any attachments) contains confidential and > proprietary information of Proxim Wireless Corporation. If you received > this message in error, please delete it and notify the sender. Any > unauthorized use, disclosure, distribution, or copying of any part of this > message is prohibited. > > > > > > > > From: Michael Ross [mailto:michael.e.r...@gmail.com] > > Sent: Saturday, June 20, 2015 6:30 AM > > To: Cor van de Water; Electric Vehicle Discussion List > > Subject: Re: [EVDL] "Zero self-discharge" (was: Bicycle battery) > > > > > > > > I think this is going to come down to semantics and word definition. > > > > > > > > I bet Popov never looks into self discharge because it is a basic non > existent occurrence in lithium ion batteries. Which is what Paul Dove and I > have been saying. I saw in the paper linked by Cor that he used self > discharge referring to capacity loss. > > > > > > > > > > > > > > > > Here is Dr. Popov's website: > > > > > http://sc.edu/study/colleges_schools/engineering_and_computing/faculty-staff/popovbranko.php > > < > http://sc.edu/study/colleges_schools/engineering_and_computing/faculty-staff/popovbranko.php > > > > > > > > > > I went through the occurrences of "lithium" in the list and copied them > for your edification below. > > > > I will pull out the ones that seem pertinent to self discharge and > capacity loss in a separate posting. Mostly that is not what Popov is > concerned with. > > > > > > > > *snip* > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150620/977f30e9/attachment.htm > > > > -------------- next part -------------- > > A non-text attachment was scrubbed... > > Name: not available > > Type: image/png > > Size: 10048 bytes > > Desc: image001.png > > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150620/977f30e9/attachment.png > > > > _______________________________________________ > > 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) > > > _______________________________________________ > 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/20150625/8f08b63b/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)
