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 <[email protected]> wrote: > On 06/19/2015 11:58 AM, Ben Goren wrote: > >> On Jun 19, 2015, at 9:33 AM, Willie2 via EV <[email protected]> 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 [email protected] <[email protected]> -------------- 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)
