A High Performance Auxiliary Power Unit for a Series Hybrid Electric Vehicle Report uri icon



  • The objective of this work was to investigate small, high-speed, gasoline engines for use in a series hybrid electric vehicle (HEV). A high performance auxiliary power unit (HPAPU) that consists of a small, high-speed engine directly coupled to an alternator was designed to provideenough power for steady state operation. A dynamic engine model was developed to characterize the performance of engines used in this design for control system development. 

    The engine model was based on previously developed heat release engine models but tailored for control system development by operating in the time domain and having a short computation time. To determine the required power output of a high performance APU in a series HEV, a steady state road load analysis program was developed using Matlab.

    One conclusion of this work was that a high performance APU weighing less than 41 kg (90 lbs.) and occupying a volume less than .09 cubic meters (3 cubic feet) can provide enough power for a 1800 kg (4000 lbs.) series HEV to operate at freeway speeds. A Yamaha 250cc, four-stroke, SI engine is the best commercially available engine for this application. The engine model was validated against its specifications.

publication date

  • November 2000



  • batteries; hybrid vehicles; emissions; modeling; engine performance, APU


report identifier

  • Report Budget Number KLK331 
    Report N01-22