500kWh/kg is really game changing. Musk estimated (quite a long time ago now) that 400kWh/kg would be the threshold for economical supersonic air transport.
On Sun, Sep 9, 2018 at 7:19 AM Jukka Järvinen via EV <ev@lists.evdl.org> wrote: > Hi guys. > > Since tZero the small-cell-paralleling has been driven by costs and the > search for benefit of scale. During those days there were not so many > ”large” cell format producers and the cost efficiency was not even close to > laptop cells. We were even looking in all kind of folding methods and > stacking techiques back then. A lot of trial and error was still ahead. > > Why small cell paralleling has an issue which will eventually render to > problems? > > Because cells age differently due plenty of different factors. If they have > fuses for their max C rate and one parallels them the current is wobbling > around between each cell unevenly. More they age more they wobble. Current > goes through where is the most lowest resistance. The fuse blows when in > high current situation the best cell tries to compensate the weak ones. > Once fuse is blown all work is done by the rest of the cells (which were > the bad ones already). This repeats until there is only few fuses left and > you’re on turtle mode. > > ”Large” format cells have less fuses as they have the same chemical mass as > maybe 10 or 15 small cells. Paralleling two or three cells one can fuse > with more relaxed sizing. Using actual large cells (>300Ah) one fuse (if > any) is enough. > > The trend is more stable chemistry cells can grow even bigger. 10.000Ah > cells have been demostrated with LiFePO4. And no fuses. > > Tesla and many other small cells users put a lot of effort to distribute > the heat as evenly as possible. This gives a lot of more time to avoid > cascade effect with blowing fuses. But this is the Modus Operandi for EOL. > It will happen. Not if. > > Now. The main question is when will the problems be there? After 200.000 or > 500.000 miles? Maybe one million miles? We are already at the point where > this does not matter. So Tesla design is very good as it is ”good enough” > and provides what it needs to. It all boils down to their cell production > and sorting methods. Or if they design an adaptive fusing setup. > > The major change is still coming to the industry as we have just now > mastered the solid state electrolyte and synthetic Graphene production. I > see now 500Wh/kg, >15 year lifetime and <$50/kWh in my horizon. We are now > already living an industrial disruption. Ejoy the (electrical) ride! > > -Jukka > > > su 9.9.2018 klo 12.54 mark hanson via EV <ev@lists.evdl.org> kirjoitti: > > > Hi Bob etc, > > > > > > > > Consumer Reports said while they loved driving a Tesla model S, they gave > > it > > a poor rating on reliability and preferred the Leaf and now the Bolt, > > saying > > "you'd be nuts not to consider a Bolt". Elon Musk/Tesla is the *only* > > company that's putting 6800+ 21mm X 70mm itty bitty cells together in a > > large EV. When they came out with the Roadster in California, I asked a > > Tesla salesman about the long term reliability of 6800 points of failure > > and > > he said "don't think of it as 6800 points of failure, think of it as 6800 > > points of redundancy". Good spin. Either they know something that *no* > > other large scale vehicle manufacturer/engineering teams doesn't, or > their > > long term reliability/profitability will continue to be poor. Knowing > what > > I know about electronic componentry, I'll put my money on large format > > cells > > for large on road EV's, Bolt, Leaf, Smart, BMW etc. > > > > > > > > Note for further info, see: www.Batteryuniversity.com EV battery > > comparisons/lithium chemistries LMC Cathode, vs LiFePO4 & aluminized > > cathode > > (tesla type) cells. > > > > > > > > Best regards, > > > > Mark > > > > > > > > > > > > Date: Fri, 7 Sep 2018 18:00:28 -0400 > > > > From: Robert Bruninga <bruni...@usna.edu> > > > > To: Electric Vehicle Discussion List <ev@lists.evdl.org> > > > > Subject: Re: [EVDL] Fwd: A comparative efficiency study of ... now > > > > Redundancy! > > > > Message-ID: <eb6dd1286c6f8c8ea943f10d95bf3...@mail.gmail.com> > > > > Content-Type: text/plain; charset="UTF-8" > > > > > > > > > I've always had it beat into my pointy engineering head to minimize > > > > > component count. Which is also why id never own a Tesla with 6800 or > > > > > so cells in their battery. > > > > > > > > That philosophy fails to recognize the value gained in multiple > redundancy. > > > > The Tesla battery of 6800 cells is far more reliable since it has 74 > cells > > in PARALLEL for each 3.6volt lithium unit. Compared to a Leaf with only > 2 > > cells in parallel at each stage in the stack. > > > > > > > > IN the Tesla the impact on any single battery failure is then only 3% of > > the > > impact of a cell problem on a car with larger format cells. > > > > > > > > I'd take the multiple redundancy of the Tesla any day. > > > > > > > > Bob > > > > > > > > > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20180908/dc82f936/attachment.html > > > > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > Please discuss EV drag racing at NEDRA ( > > http://groups.yahoo.com/group/NEDRA) > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20180909/925cf394/attachment.html > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Michael E. Ross (919) 585-6737 Land (919) 901-2805 Cell and Text (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Tablet, Google Phone and Text -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20180909/f6d8dae5/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
