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Neil Johnson of the Navitas Systems Advanced Solutions Group gave the gathering at the ninth annual Electric Aircraft Symposium an overview on battery reserve limits and gauging, and the methods necessary to address the different failure modes for lithium batteries, all of which could be problematic for electric aircraft. Navitas includes some legacy technology adapted from 123 Systems, typically 18650 format batteries, an 18-millimeter by 65-millimeter cylinder with active materials separated by a dialectric separator material in a “Tootsie Roll” configuration.  Some of the chemistries involved were developed for Formula 1 racers, and according to a talk given by Bill Dube’ and Eva Håkansson, are considerably more powerful than “conventional” lithium cells. According to Neil, the five billion cells out there now have been vetted using failure mode and effects analysis (FMEA) and fault tree analysis (FTA), two methods of statistically analyzing failure modes and of determining what might become failure modes in new designs. FTA. As Neil shared with the audience, …