Journal of Applied Science and Engineering

Published by Tamkang University Press

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The Effects Of Battery Initial State Of Charge On The Energy Distribution Of Vehicles Under WLTC Driving Cycle

 2026

 Volume 34

Jie Zhang1, Xiaobing Wu2, Hongwei Guo1, and Tao Wu3

1School of Automobile, Zhejiang Institute of Communications, Hangzhou 311112, China

2Zhejiang Technology Innovation Service Center, Hangzhou 310007, China

3School of Mechanical and Automotive Engineering, Shanghai University of Engineering Science, Shanghai 201620, China

Received: May 13, 2026
Accepted: August 01, 2026
Publication Date: August 12, 2026

上傳圖片

Schematic diagram of energy flow topology of the test vehicle 

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During vehicle operation, the initial state of charge (ISOC) of the onboard battery affects the control strategies governing battery and generator operation, which in turn influences the vehicle’ s energy distribution. In this study, an SUV equipped with an intelligent start-stop system and braking energy recovery was tested on a chassis dynamometer under the worldwide harmonized light vehicles test cycle (WLTC) to investigate the effects of three battery ISOC levels– 45%, 70% (battery threshold), and 85%– on vehicle energy distribution. The results show that ISOC exerts a significant influence on battery and generator operation, thereby affecting energy recovery efficiency. A battery ISOC of 85% favors improved vehicle energy efficiency and reduced fuel consumption. Conversely, at an ISOC of 45%, the vehicle exhibits the highest fuel consumption, an increase of more than 8%, indicating that operation with an ISOC substantially below the threshold should be avoided. This study develops a practical experimental method that links the easily measurable ISOC parameter to holistic vehicle energy performance, offering a novel and efficient approach to indirectly evaluate how gradual battery degradation affects vehicle fuel economy without the need for long-term aging tests.

Keywords: initial state of charge; battery; energy distribution; energy recovery; WLTC

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