Power and life enhancement of battery-electrical double layer capacitor for hybrid electric and charge-depleting plug-in vehicle applications

The performance of a battery-EDLC hybrid power source under pulse-operated power systems is theoretically and experimentally analyzed. Electrical double layer capacitors (or EDLC) enhance the power of lead-acid battery as it acts as a buffer in charging and discharging. Consequently, this hybrid technology is able to provide and absorb charge rapidly during vehicle acceleration and braking. The experimental results show considerable extension of runtime and reducing of internal losses. Using this association, the battery current draw is reduced and the EDLC source supplies the majority of transient current. As a result the battery stress is reduced up to 58%. Other laboratory tests showed a substantial improvement over stand-alone lead-acid battery pack and the lifetime of the battery is increased with 30%. This article proposes a new approach to perform accelerated life cycle analysis of lead-acid batteries with/without EDLC based on Dynamic Endurance Test according to standard IEC 61982-2. At least the power capabilities and internal resistance characteristics during charge/discharge of this technology have been evaluated by hybrid pulse power characterization test (HPPC). This paper introduces further new definition of the battery stress in terms of battery current and depth of discharge. (C) 2010 Elsevier Ltd. All rights reserved.