Hi David, others. I think the "packing" argument is ignoring one big issue that totally flips the equation around, in addition to a few other considerations.
Look at popular prismatic cells: there are space-efficient pouches inside, but the walls of the cells have to be tough and thick to contain the swelling and pressure that the pouches can exert when charging. Even in modern modules that use pouches like Leaf batteries, there still is an aluminum frame around the pouch cells to contain them and on top of that, they need large and heavy end-plates to clamp down those modules to prevent the pouches from swelling and damaging the cells. In cylindrical batteries, not only is the container the minimal surface shape to contain the cell (for a certain length) but also a thin metal container is all that is needed to contain the pressure in the cell, since it has the right shape to bear the forces in itself. So, the minimal amount of material is needed and it is packed pretty efficiently. I am sure someone can do the math and figure out at which wall thickness and cylinder diameter the cross-over point is that cylindrical is actually *more* space efficient than prismatic. Note that empty space between cells is not "lost" if it is used for cooling the cells, just like prismatic or pouch packs require additional infrastructure for cooling - or take a gamble without cooling as in the Leaf. Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: cwa...@proxim.com Private: http://www.cvandewater.info Skype: cor_van_de_water XoIP: +31877841130 Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 -----Original Message----- From: EV on behalf of EVDL Administrator via EV Sent: Fri 4/14/2017 9:50 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Tesla cell size On 13 Apr 2017 at 22:04, Michael Ross via EV wrote: > A cylinder only has to be oriented for polarity, it > can have any radial orientation. We had a rather similar discussion here many years ago (20?) about Optima lead batteries, which used (and still use) cylindrical cells. This thread has named some of the advantages of cylindrical cells. Those aren't insignificant by any means. However, a cylinder isn't as efficient as a rectangle if your goal is to package the most active material per unit of available vehicle space. The exception to this would be a case where the form factor matches the container perfectly, such as filling the round frame tubes of an e-bike with cells. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 4379 bytes Desc: not available URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20170414/0a266df0/attachment.bin> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
