TU Berlin

Electrical Energy Storage TechnologyChair

Page Content

to Navigation

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)


Determination of the Distribution of Relaxation Times by Means of Pulse Evaluation for Offline and Online Diagnosis of Lithium-Ion Batteries
Citation key batteries7020036
Author Goldammer, Erik and Kowal, Julia
Year 2021
ISSN 2313-0105
DOI 10.3390/batteries7020036
Journal Batteries
Volume 7
Number 2
Abstract The distribution of relaxation times (DRT) analysis of impedance spectra is a proven method to determine the number of occurring polarization processes in lithium-ion batteries (LIBs), their polarization contributions and characteristic time constants. Direct measurement of a spectrum by means of electrochemical impedance spectroscopy (EIS), however, suffers from a high expenditure of time for low-frequency impedances and a lack of general availability in most online applications. In this study, a method is presented to derive the DRT by evaluating the relaxation voltage after a current pulse. The method was experimentally validated using both EIS and the proposed pulse evaluation to determine the DRT of automotive pouch-cells and an aging study was carried out. The DRT derived from time domain data provided improved resolution of processes with large time constants and therefore enabled changes in low-frequency impedance and the correlated degradation mechanisms to be identified. One of the polarization contributions identified could be determined as an indicator for the potential risk of plating. The novel, general approach for batteries was tested with a sampling rate of 10 Hz and only requires relaxation periods. Therefore, the method is applicable in battery management systems and contributes to improving the reliability and safety of LIBs.
Link to publication Download Bibtex entry


Quick Access

Schnellnavigation zur Seite über Nummerneingabe