I agree with Cor. I have examples of Thundersky, CALB, and GBS LiFePO3 cells that have failed by turning into resistors.
>From: EVDL Administrator via EV <ev@lists.evdl.org> >You would need 2 BMSes, but IMO (I am not an expert) it would be safer to >make 2 series strings, and then parallel the strings. That's the method I've used. The two strings are also not connected directly in parallel. If a cell in either string fails shorted, the higher-voltage string dumps *all* its power into the lower-voltage string. This can kill the good string, overcharge the bad string, and set Fire to the shorted cell! Instead, add a commoning diode in series with each string (anode to +, cathode to main contactor + (to controller +). These diodes prevent the higher-voltage string from feeding current into the lower-voltage string. The commoning diodes are BIG -- they have to carry the maximum battery current. For charging, you need a second pair of commoning diodes from the charger + to each string's +. These diodes can be much smaller, as they only need to carry the charger's maximum current. -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com _______________________________________________ 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)
