Battery

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  • Topic: Rechargeable battery, Lithium, Car battery
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  • Published : April 19, 2013
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Electrical Battery Model for Use in Dynamic Electric Vehicle Simulations Ryan C. Kroeze, Philip T. Krein
University of Illinois at Urbana-Champaign Department of Electrical and Computer Engineering 1406 W. Green St. Urbana, IL 61801 Tel.: 217-333-6592, Fax: 217-333-1162 Email: rkroeze2@uiuc.edu, krein@uiuc.edu

Abstract - Simulation of electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles over driving schedules within a full dynamic hybrid and electric vehicle simulator requires battery models capable of predicting state-of-charge, I-V characteristics, and dynamic behavior of different battery types. A battery model capable of reproducing lithium-ion, nickel-metal hydride, and leadacid I-V characteristics (with minimal model alterations) is proposed. A battery-testing apparatus was designed to measure the proposed parameters of the battery model for all three battery types and simulate driving schedules with a programmed source and load configuration. A multiple time-constant battery model was used for modeling lithiumion batteries; verification of time constants in the seconds to minutes and hour ranges has been shown in numerous research articles and a time constant in the millisecond range is verified here with experiments. Lack of significant time constants in the millisecond range is validated through direct testing. A modeled capacity-rate effect within the state-of-charge determination portion of the proposed model is verified experimentally to ensure accurate prediction of battery state of charge after lengthy driving schedules. The battery model was programmed into a Matlab/Simulink environment and used as a power source for plug-in hybrid electric vehicle simulations. Results from simulations of lithium-ion battery packs show that the proposed battery model behaves well with the other subcomponents of the vehicle simulator; accuracy of the model and prediction of battery internal losses depends on the extent of tests performed on the battery used for the simulation. Extraction of model parameters and their dependence on temperature and cycle number is ongoing, as well as validation of the Simulink model with hardwarein-the-loop “driving schedule” cycling of real batteries. Keywords: plug-in hybrid electric vehicle, lithium-ion battery, vehicle simulator, battery model

developed through the National Renewable Energy Laboratory (NREL) [1] is a simulator based on static maps that reflect steady-state behavior of vehicle subsystems. A dynamic simulator [2]-[3] offers a more detailed look, based on dynamic equations of each subcomponent (the engine, battery, inverter, motor, and transmission) on microsecond time scales. The Simulink component block of the battery model in [2-3] was designed for vehicles with lead-acid battery packs. The lead-acid model is insufficient for accurate simulations of vehicle drivetrains with different battery-pack chemistries. Here, a three time-constant dynamic electric battery model for lead-acid, nickel metal hydride (NiMH), and lithium ion (Li-ion) batteries is proposed and developed for use within a dynamic HEV simulator. The electrical model must both accurately represent the terminal voltage, state-of-charge (SOC), and power losses of each battery type, without excessive simulation times. The paper includes experimental validation of the models and simulator at several levels. II. BACKGROUND

I.

INTRODUCTION

Electrochemical batteries are used in conjunction with an auxiliary power unit (APU) to power hybrid electric vehicles (HEV). Plug-in hybrid electric vehicles (PHEV) and electric vehicles (EV) can be treated as a subclasses of HEVs in which the batteries function in different ways. In order to better understand losses, thermal characteristics, and durability of various drivetrains, a dynamic simulator is a key tool. The ADVISOR program

In the search for a battery model to meet the above specifications, electrochemical, mathematical,...
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