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We try to understand the fast recharge capability of automotive lithium-ion batteries and its effect of fast charge on capacity degradation. We find out that 5 Ah prismatic Li-ion cells can be fully recharged in 3 minutes under a constant rate of 20C, or in 2 min (25.5C) from 0% to 85% state of charge (SOC) without undue stresses. We cycle the battery at 16C charge rate from 0 to 100%SOC and do not see any unexpected battery capacity loss in 50 cycles, where half of the cycles are charged at1C-rate as a reference capacity check. We realize that the batteries under the fast charge tests do not experience any negative impacts related to mass transport in either solid electrodes or the electrolyte system. In the paper, we propose a new procedure to measure the ac and dc resistances of the battery under continuous operation. Electrochemical impedance analyses on the whole battery and the individual electrodes are also conducted.

The transition from nickel metal-hydride (NiMH) battery technology to lithium ion (Li-Ion) battery technology in hybrid electric vehicle applications presents both new opportunities and new challenges for vehicle implementation. Full recognition and acceptance of these opportunities and challenges is necessary for the vehicle manufacturer to efficiently proceed towards production implementation of Li-Ion battery technology in hybrid electric vehicles, even for those vehicle manufacturers who are already fully experienced with the significant prerequisite of NiMH battery technology implementation in vehicle applications.

Novel testing procedures and analytical methodologies to assess the performance of hybrid electric vehicle batteries have been developed. Tests include both characterization and cycle life and/or calendar life, and have been designed for both Power Assist and Dual Mode applications. Analytical procedures include a battery scaling methodology, the calculation of pulse resistance, pulse power, available energy, and differential capacity, and the modeling of calendar- and cycle-life data. Representative performance data and examples of the application of the analytical methodologies including resistance growth, power fade, and cycle- and calendar-life modeling for hybrid electric vehicle batteries are presented.