The cells in the TESLA pack are a group in parallel then the parallel groups are wired in series for the desired voltage, The key to pack survival when a cell fails is a fusible link (Correctly sized short length of wire) in series with each and every cell then any malfunctioning cell is isolated when the link opens. (Reducing pack capacity about 2%.)
Dennis Lee Miles (*[email protected] <[email protected]>)* * Founder: **EV Tech. Institute Inc.* *Phone #* *(863) 944-9913 (12 noon to 12 midnight Eastern US Time)* *Educating yourself, does not mean you were **stupid; it means, you are intelligent enough, **to know, that there is plenty left to learn!* * You Tube Video link: http://youtu.be/T-FVjMRVLss <http://youtu.be/T-FVjMRVLss> * * NEW You Tube Video link: *http://youtu. be/Pz9-TZtySh8 <http://youtu.%20be/Pz9-TZtySh8> On Tue, Aug 19, 2014 at 7:32 PM, Lee Hart via EV <[email protected]> wrote: > Peri Hartman via EV wrote: > >> To take this to a traction pack, I would want to try a similar design >> where strings of cells are spot welded in parallel for the desired >> current load. As I understand it, you can put as many in parallel as you >> want and control them with a single BMS unit. >> > > Well... There are those that believe this, and it is certainly done. > > However, think about failure modes: Sooner or later, a cell will fail. > What happens if one of the cells in parallel shorts? All the rest will dump > all their stored energy into that one shorted cell. That is very likely to > result in a burst cell or even a fire. And packed like this, once one cell > starts burning, it can set the rest on fire. > > When laptop manufacturers connected their cells directly in parallel, > there were some dramatic failures and fires. Since then, reputable > manufacturers are using cells with *internal* fuses and safety devices. > Hobbyists and el-cheapo manufacturers aren't likely to use such cells. > > -- > The principal defect in a storage battery is its modesty. It does not > spark, creak, groan, nor slow down under overload. It does not rotate. > It works where it is, and will silently work up to the point of > destruction without making any audible or visible signs of distress. > -- Electrical Review, 1902 > -- > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.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) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140819/de521326/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)
