Statistical Analysis Applied to Ni-MH Battery Impedance for Preservation

Abstract

  Battery-powered prime mover vehicles, i.e., electric vehicles (EVs) and hybrid electric vehicles (HEVs), of which drive train system shall be applied for traction drive type gantry cranes at the port and harbor facilities. The battery has a chemical degradation both cycle and preservation time. The battery verification shall be done in both aspect of the battery cycle lifetime experiment and the battery preservation lifetime experiment. Though it is a fact that the most of the experiment which does not verify the battery preservation lifetime but the battery cycle lifetime prior to the battery mass production. Owing to an allowable research and development span, there is not enough time to verify the battery preservation lifetime experiment which makes hard to estimate the battery total life in actual usage. This study investigates a possibility extent that an AC impedance response analysis, which method can verify the battery deterioration condition in progress of cycle lifetime experiment which was previously reported ^[1], and also apply to verify the battery deterioration condition in progress of preservation periods and the estimation life time. The battery is focused on a Nickel-metal hydride (Ni-MH) battery which is widely used as traction energy storage in HEVs. The AC impedance response analysis is an appropriate method which can be detected easily to measure the battery deterioration level of an amount of the battery's self-discharge, a nominal type of Ni-MH battery called AB5 alloy type. The final objective of this study is verified that the AC impedance response with a statistical analysis is an effective method to verify the battery deterioration level in progress of preservation easily and to estimate the battery total life time.