Journal
ENERGY
Volume 39, Issue 1, Pages 310-318Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.energy.2012.01.009
Keywords
State-of-charge; Open-circuit voltage; Equivalent circuit model; Online estimation; Electric vehicles
Categories
Funding
- National High Technology Research and Development Program of China [2010AA112304]
- Chinese Ministry of Science and Technology [2010DFB70090]
- National Natural Science Foundation of China [50905017]
- research foundation of National Engineering Laboratory for Electric Vehicles
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This paper presents a method to estimate the state-of-charge (SOC) of a lithium-ion battery, based on an online identification of its open-circuit voltage (OCV), according to the battery's intrinsic relationship between the SOC and the OCV for application in electric vehicles. Firstly an equivalent circuit model with n RC networks is employed modeling the polarization characteristic and the dynamic behavior of the lithium-ion battery, the corresponding equations are built to describe its electric behavior and a recursive function is deduced for the online identification of the OCV, which is implemented by a recursive least squares (RLS) algorithm with an optimal forgetting factor. The models with different RC networks are evaluated based on the terminal voltage comparisons between the model-based simulation and the experiment. Then the OCV-SOC lookup table is built based on the experimental data performed by a linear interpolation of the battery voltages at the same SOC during two consecutive discharge and charge cycles. Finally a verifying experiment is carried out based on nine Urban Dynamometer Driving Schedules. It indicates that the proposed method can ensure an acceptable accuracy of SOC estimation for online application with a maximum error being less than 5.0%. (c) 2012 Elsevier Ltd. All rights reserved.
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