Cell Level Power Electronics for Better Battery Management System

Abstract

In this master thesis, a comparison between two types of battery packs for Electric Vehicles (EVs) is made. Pack 1 is a conventional cells battery pack where all the cells are connected in series. Pack 2 is an autonomous cells battery pack whose cells are equipped with individual micro DC-DC converters. Pack 1 is compared against Pack 2 for energy output (kWh), charging characteristics and ageing. The comparison is performed for two different driving profiles the New European Drive Cycle (NEDC) and a tested and modelled use case. The DC-DC converter makes Pack 2 the autonomous cells battery pack even though the cells are the same. The DC-DC converter ensures load management on individual cell level. Load balancing leads to several advantages in the energy output, charging characteristics, slower ageing rate and susceptibility to capacity spread of the cells forming the battery pack. The battery pack performances are analysed and compared to show that the performance of Pack 2 is better for both NEDC and use case driving profiles. A final sensitivity analysis comparing the battery pack ageing is performed for various use cases thus, giving the holistic view of the advantages in the technology used.