Burke, Andrew (2002) Cost-Effective Combinations of Ultracapacitors and Batteries for Vehicle Operations. Institute of Transportation Studies, University of California, Davis, Presentation Series UCD-ITS-RP-02-37
High power, pulse batteries and ultracapacitors have been under development for the past 5-10 years as part of an effort world wide to develop electric and hybrid-electric vehicles that are cleaner and more efficient than conventional ICE powered vehicles. For much of that time, the two technology were considered to be in competition for use in hybrid vehicle applications. Up to the present time, batteries have been the technology of choice in the hybrid vehicles brought to market (the Prius and Insight) and most of the prototype vehicles being tested by various auto companies also use batteries. Most passenger cars use nickel metal hydride batteries or in one case, lithium-ion. The large hybrid vehicles (buses and trucks) use lead-acid primarily due to cost considerations. Ultracapacitors are presently being considered by a number companies for hybrid vehicles as some of the problems involved with using batteries in these applications become more evident (life and thermal management). This paper discusses the possible advantage of combining batteries and ultracapacitors with the ultracapacitor providing the high power capability (kW) in both acceleration and deceleration and the battery providing the energy storage (kWh) for recharging the capacitors and supplying accessory loads. Various combinations of carbon-based ultracapacitors and batteries (lead-acid, nickel metal hydride, and lithium ion) are discussed for several applications, including 42V mild hybrids and high voltage systems for full-hybrid cars and buses.