TU Berlin

Electrical Energy Storage TechnologyChair

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Prof. Dr.-Ing. Julia Kowal

Julia Kowal

Room: EMH 163


Einsteinufer 11

Sec. EMH 2

10587 Berlin

Phone: +49 (0)30 314-25394

Fax:     +49 (0)30 314-21133


Consultation hours: On Mondays 9 - 10 h and on appointment. In summer semester 2022 (25.4.-18.7.), the consultation hour will be from 10-11 h.

In most weeks, I am in the office on mondays, so a personal meeting is possible again. To be sure, please ask before you come. Alternatively, you can phone me or we can arrange a Zoom meeting.


since 03/2014
Chair of Electrical Energy Storage Technology at the TU Berlin
01/10 - 02/14
Senior engineer at the department of Electrochemical Energy Conversion and Storage Systems, ISEA, RWTH Aachen
PhD at RWTH Aachen, Topic: "Spatially-resolved impedance of nonlinear inhomogeneous devices - using the example of the lead-acid battery"
Visiting researcher at the company Exide in Azuqueca de Hénares, Spain
Visiting Researcher at the research centre RISØ in Roskilde, Denmark
Research assistant at the department of Electrochemical Energy Storage Conversion and Systems at the Institute For Power Electronics and Electrical Drives (ISEA), RWTH Aachen
Studies of electrical engineering at RWTH Aachen Diploma thesis: "Investigation of the thermal behaviour of electrochemical energy storage systems in vehicle on-board power supplies"



Awards and Scholarships
Herbert-Kind-Price of ETG in the VDE
Brigitte-Berkenhoff-Price for the best graduate in the field of electrical engineering at RWTH Aachen
Aachen's VDE price
Sponsorship through the Prof. Dr. Koepchen Merit Foundation (RWE)


A Method for Detecting the Existence of an Over-Discharged Cell in a Lithium-Ion Battery Pack via Measuring Total Harmonic Distortion
Citation key batteries8030026
Author Kim, Jonghyeon and Kowal, Julia
Year 2022
ISSN 2313-0105
DOI 10.3390/batteries8030026
Journal Batteries
Volume 8
Number 3
Abstract This paper deals with a method to detect the existence of an over-discharged cell in a lithium-ion battery (LIB) pack by measuring the total harmonic distortion (THD) rate in the voltage response. Over-discharge of the LIB cell reduces the available capacity by irreversible chemical reactions, resulting in serious safety risks such as explosions. Even if only one over-discharged cell exists in the battery pack, it accelerates the decomposition of other cells. In general, the measurement of each cell voltage in a battery pack is required to detect one over-discharged cell. This is because if only the voltage of the battery pack is measured, it cannot be distinguished whether the voltage of each cell is uniformly low or one specific weak cell is over-discharged. The proposed method measures the frequency response through the voltage at only two terminals of the battery pack to detect the presence of one over-discharged cell. When the battery cell is discharged beyond a certain level, the system nonlinearity of the battery pack increases, and it can be detected from the increased THD rate of the battery pack. The proposed method is verified by simulation and measurement.
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