I think the main asset of LFP is it takes an extra 100C or so to ignite the electrolyte. They can burn just not as well as others) LFP has some real disadvantages too. It is somewhat more costly to manufacture due to it being necessary to make the positive electrode in an inert atmosphere.
LFP cells are not compact (low volumetric density) They start to deteriorate badly at a pretty low temperature when fully charged- 40°C (104°F). I have unfortunately applied this last detriment to my own LFP packs for my LEV. Jeff Dahn mentioned another chemistry that had an upper limit of 35°C (95°F). Information on the temperature stability of cells is not widely known or complete across all cell types. (If I had a spare quarter of a million to buy the test equipment I would love to characterize all that.) See page 3 https://www.bcg.com/documents/file36615.pdf for pcomparison of properties for Li Ion cells. Flat curve doesn't compete with more capacity in my mind. It may mean a BMS has to be a better design with more precise and accurate control. A less flat curve might mean you can detect a good upper cutoff voltage more easily. Getting that last little bit of capacity into a cell is a good way to trash it. A really good way to get more life from a cell is to cut it off high and low, giving up a decent proportion of capacity in the meantime. Your choice. Tesla packs are large at least in part so they can not charge them fully, and not discharge them fully. On Fri, Mar 27, 2015 at 11:32 AM, tomw via EV <[email protected]> wrote: > Actually I think the "flat" V versus capacity of LFP is an asset. It is > what > enables you to use Ah used, a nice stable, repeatable measurement, that > tracks Wh used quite well over most of the capacity of the pack (I've data > logged battery V and I using 1 sample/sec and compared them). I've used a > TBS gauge (like Willy) for over 5 years now, and kept track of Ah used to > various destinations in a 3x5 notebook I keep in the glove box. As a > result, I can look at a route on google maps and from the distance and > elevation change estimate to typically within a few percent how many Ah it > will take to get there (like David mentioned with the Solectria). A > computer could learn that way to...if only David would give it his > destinations. :^)) You can't expect all drivers to track things that way > though, they just want to get in and go without checking anything. > > > > -- > View this message in context: > http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-EVLN-LEAF-EV-Pack-Reliability-Outperforms-Cynics-Critics-tp4674498p4674575.html > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.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) > > -- 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/20150327/05df6441/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)
