Vehicle manufacturers worldwide have recognized the trend toward increased on-board power demands is causing a need to raise the electrical system voltage from the present standard of 12 V to a higher, yet safe, voltage. One of the major challenges emerging from the transition to higher voltages is the size, weight, volume, cost and complexity of the energy storage system required to support the vehicle system and its loads. This paper discusses these changes, their implications, and presents potential solutions to address the future needs of vehicle manufacturers. (C) 2001 Elsevier Science B.V. All rights reserved.