Yes, if one really wants to protect from cell failure then fuse each cell like Tesla does.
Sent from my iPad > On Jun 19, 2015, at 1:33 PM, Michael Ross via EV <ev@lists.evdl.org> wrote: > > I said it, because it has come up in papers and journal articles I have > read. Paul agreed with me I think. > > The basic Li ion cell does not self discharge - none of them. Once charged > they will just sit there and remain asis until something creates a circuit > for the ions to migrate back to the positive electrode. > > I don't understand the mechanism for PbSO4, but they do discharge just > sitting unattached to any circuit - all of them. > > What this says is if a cell is having ions migrate back to the positive > electrode that something is wrong. There are all sorts of manufacturing > defects that can cause it, or BMS deficiencies, etc. No amount of > correction to a lead acid will stop it from discharging. > > If you tell me that your Thundersky cells shows a loss over time, I don't > disbelieve that - I say instead, they needed more and better design work > and some manufacturing improvement. There is some sort of fault causing an > internal or external parasitic load. > > The prismatic, folded page cells, like CALB and TS are not very good in > many respects, Some (all?) bolt the conductive plates onto an aluminum > post with a threaded fastener. Bleh. > > Notice that folks like Tesla did not choose that form - even though the > alternative was to make individual connections to 7000 smalls to accomplish > the task. > > Those little cylindrical cells have some advantages. > > They lend themselves to very automated, read consistent, construction. > Consistency is very important at the pack level. > The cylindrical form is much more stable when subjected to the volumetric > changes that Li ion cells undergo when charging and discharging. > They can't be packed too close that they cannot convect heat well (with > some extra gear to puch air (or other fluids around them). > Internally the cylindrical cells are simpler with less opportunity for > failure. > The connection to a pack by welding is as good as it gets. > And so on. > > I am pretty sure in that video by Jeff Dahn I keep alluding to (and > linking) he mentions this characteristic of Li ion cells. > > Did you all notice that article Bruce linked to about Tesla funding > research at the Dahn Lab? I am hoing the Tesla will make these results > open to all as they have so many other things in the interest of furthering > the use of EVs. > > Look forward for new information, rather than back to the old and less well > done research. Stuff we read from 2009 is quite stale WRT Li cells. > > Mike > > > > > >> On Fri, Jun 19, 2015 at 1:15 PM, Willie2 via EV <ev@lists.evdl.org> wrote: >> >>> On 06/19/2015 11:58 AM, Ben Goren wrote: >>> >>> On Jun 19, 2015, at 9:33 AM, Willie2 via EV <ev@lists.evdl.org> wrote: >>> >>> I am curious as to how Paul came to his belief. >>> His methodology is inadequate to the task -- rather like using a roadside >>> truck scale to weigh the first four people to pass by and concluding that >>> all humans weigh exactly 200 pounds. >> You may be implying that Paul attempted to deduce self discharge from cell >> voltage? >> >> When my first lithium pack was new, I was frequently amazed that NUMEROUS >> EV folks with extensive lead experience would put a volt meter to my cells >> and proclaim: "Why these cells are PERFECTLY balanced!" I don't know how >> many times I've attempted to explain that it is almost impossible to >> determine state of charge from voltage on lithium cells. Other than at the >> tails, of course. >> >> Though I don't know that Paul made that mistake. >> >> >> _______________________________________________ >> 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/20150619/a90c49e5/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) > _______________________________________________ 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)
