Lithium ion battery system using amorphous carbon in negative electrode and its management technology for HEV applications

Abstract

We have developed the lithium ion battery system using amorphous carbon in negative electrode and its management technology for hybrid electric vehicle (HEV) applications. The cell has an output power density as high as 3000 W/kg at 50 % state of charge (SOC) and 25 deg.C, and the 48-cell battery module has an output power of 43 kW. To enable effective and adequate use of this high power battery, we have developed new architecture characterized by the newly developed battery control IC, daisy chain communication circuit without isolator and the decentralized control configuration of cell controller and battery controller. Then, we have determined suitable battery control parameters, such as SOC, state of health (SOH) and allowable current/power, taking into consideration the battery characteristics which mainly result from amorphous carbon, system particulars of IIEVs, and the purpose of these parameters. They were adopted into the software of the battery controller. Both software and hardware of the battery controller is made in the form of platform. Because of the excellent characteristics of this battery, its intrinsically reliable controllability, and the platform for battery control technologies, the battery system is promising not only for HEVs, but also for other applications that require both high power and reliability such as a hybrid electric train.