Cor, Remember that there is a demand from people for some self discharge number. What easier way than just to make up a number? Maybe that is what they did and maybe that isn't. Lets not confuse capacity loss with self discharge. Also, a voltage measurement on a cell left to sit with no load doesn't prove self discharge either. Your analogy of an ideal circuit can't be used to size wiring doesn't apply because the theory does include resistance. I know what you are trying to say, however. It is just that so many people believe that self discharge exists and keep speaking it that many, including those who should know better, ignore things to justify their position. IIRC, you were one who told me that my battery pack would be way out of balance in a short period of time if I took my BMS boards off. Well, 4 years later and it hasn't happened. I say this, not to imply you don't know anything, but to show that we always need to be open to the fact that we might have missed something.
Watch https://youtu.be/9qi03QawZEk. From the description: 'Published on Sep 6, 2013 On July 30th, 2013, Professor Jeff Dahn of Dalhousie University delivered a lecture entitled "Why do Li-ion batteries die and can they be immortal?".' If you don't want to watch all 1:13:30 of it, which everyone on this list really should, skip to 1:09 where he directly answers the question about a charge shuttle reaction. He clearly said that no Li battery has one built in. Watch to the whole lecture where other things about Li cells are addressed. On Fri, Jun 19, 2015 at 5:11 PM, Cor van de Water via EV <[email protected]> wrote: > David, > > Why do all manufacturers of Li-Ion batteries specify the amount of > self-discharge > and why do people like me who monitor Li-Ion batteries over time, see and > measure > the self-discharge? > I understand that you say "theoretical" the pure Li-Ion cell may not have a > self discharge mechanism and thus the actual present self-discharge appears > to be > a spurious effect, possibly caused by contamination, so the amount of > self-discharge > is a quality indicator of the (lack of) contamination in the cell... > > However, saying that the ideal (theoretical) cell does not have any > self-discharge is as valuable > as saying that the ideal (theoretical) connection does not have any > resistance. > In practice however you better take that resistance into account when sizing > your wiring and connections. > Similar to taking self-discharge (and especially the difference in > self-discharge between cells) into account > when designing a battery pack. > > 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 > 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. > > > -----Original Message----- > From: EV [mailto:[email protected]] On Behalf Of David Nelson via EV > Sent: Friday, June 19, 2015 4:37 PM > To: Bill Dube; Electric Vehicle Discussion List > Subject: Re: [EVDL] "Zero self-discharge" (was: Bicycle battery) > > Bill, > > I have dug through many scientific papers on Li batteries and how they work > and I haven't been able to find anything about a theoretical self-discharge > mechanism. I have found some explicitly talking about the lack of a charge > shuttle mechanism like in lead-acid batteries, however. > > One paper I read has a section devoted to figuring out a charge shuttle > mechanism to add to a Li cell. It isn't a paper for the faint of heart, > however. It is "Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable > Batteries" by Kang Xu published in the Chemical Review, 2004, Vol. 104, No. > 10, pp. 4303-4417 and published on the web 09/16/2004. > > While I'm sure I don't get it 100% of the time I try to make sure I say, > "LiFePO4 cells have no theoretical self discharge mechanism." > This, according to all I have been able to find on the cells, is true. > Also, the most ardent anti-BMS people I have found have in fact done a lot of > searching of the scientific literature and came to the same conclusion. It > was not just something they made up to support their anti-BMS position. > > If you have other literature showing what the self-discharge mechanism is > please share it. > > On Fri, Jun 19, 2015 at 11:46 AM, Bill Dube via EV <[email protected]> wrote: >> This "zero self-discharge" myth seems to be a common thread with the >> "anti-BMS" crowd. I don't know where this misinformation comes from. >> >> All cells have self-discharge. It is just a matter of degree. >> Also, the self-discharge varies from cell to cell. That's why you need a BMS. >> These are well-documented facts for all those that care to >> investigate, either through the scientific literature or by simply >> systematically testing cells for themselves (as Lee Hart has done.) >> >> I strongly suspect the "zero self-discharge" myth comes from >> the same unscientific source that the anti-BMS myth has sprung from. >> >> Bill D. >> >> _______________________________________________ >> 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) >> > > > > -- > David D. Nelson > http://evalbum.com/1328 > http://www.levforum.com > _______________________________________________ > 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) > -- David D. Nelson http://evalbum.com/1328 http://www.levforum.com _______________________________________________ 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)
