This paper presents simulation and experimental realization of 42 V Power Net for automotive auxiliary on-board applications. For energy storage. a pack of supercapacitors is used in parallel with a battery. For simulation, the mathematical models of battery, DC/DC converters and supercapacitors are developed using MATLAB/SIMULINK(R). An experimental power test bench has been designed. The 42 V Power Net voltage and the load current of supercapacitors are controlled by a microcontroller. Simulation results and experimental ones are presented, compared and analysed. (c) 2005 Elsevier B.V. All rights reserved.