NHTSA Preliminary Evaluation PE99075

ODI has received information alleging failure of the equalizer on the vehicles listed above.An equalizer provides a 12volt source from a 24 volt battery; in effect, two 12 volt batterier get equally charged in series from a 24 volt source, and equally discharged in parallel into a 12 volt load.The equalizing term refers to the distribution of charge and discharge energy between the two separte 12 volt batteries. When the failure occurs the equalizer smokes excessively, filling the bus with smoke.As these buses may be carrying 50 or more people, excessive smoking (with possibility of a fire) is a concern.A fire may also result.A preliminary evaluation is being opened to gauge the scope of the issue, the technical causes of the equalizer failures and to address the resulting public safety concerns.