Battery Requirements for HEVs, PHEVs, and EVs: An Overview

This chapter describes the battery properties in different electric vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and EVs and presents some examples of related recent developments. Pure EVs need the largest amount of energy with the smallest weight possible, whereas the batteries for HEVs provide the maximum power in a minimum size. The battery price and size are particularly critical for EVs because the amount of energy required for achieving a sufficient range and the price of the new Li batteries which provide the minimum distance of 150–200 km required for EVs is the biggest hurdle in the commercialization of these vehicles. The batteries for plug-in HEVs (PHEVs) have a medium power/energy ratio and are bigger than HEV batteries, and therefore more expensive. The second important contribution to the total cost is the battery assembly and management system that is required to insure the correct monitoring of the multiple cells assembly during discharge and charge, which in turn, is essential to insure the required reliability and safety of the system. The engine and electric motor in full hybrids (power assist HEVs) contribute to powering the car, with electric power being used for starting and acceleration. Presently the Li–ion battery is the only system being considered for powering PHEVs because of its high specific energy and energy density, although its properties are still considered insufficient.