Julia Kowal | TU Berlin (original) (raw)

Papers by Julia Kowal

World Electric Vehicle Journal, Jun 28, 2018

Batteries, Mar 17, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

The diagnostics of the aging of lead-acid batteries is an important topic for applications in the... more The diagnostics of the aging of lead-acid batteries is an important topic for applications in the automotive and stationary sector. Lead-acid batteries, especially as starter batteries, are still by far the most widely produced battery technology. The impedance of the battery is an easy parameter to determine, but in the past no clear dependencies between impedance change and ageing were found. This was due to a lack of control of the boundary conditions and failure to consider the dependencies of the impedance on state-of-charge, current rate and temperature. Furthermore, often only single impedance values were considered. In this thesis, electrochemical impedance spectroscopy (EIS) on lead-acid batteries was applied with regard to ageing estimation and the determination of parameters of electrochemical processes. Test cells were constructed with two positive and one negative electrode in order to obtain the state of the electrodes as homogeneous as possible. At the test cells two different ageing processes relevant for the lead-acid battery were forced; on the one hand the corrosion of the positive electrode and on the other hand the accumulation of the discharge product (lead sulphate) at the surface of the negative electrode (sulphation). During these tests, EIS measurements with superimposed charge and discharge currents were regularly carried out together with capacity tests. At the end of the tests the amount of corroded material and lead sulphate was determined. Due to the sulphation, characteristic changes in the spectrum of the negative electrode could be observed, while the spectrum of the positive electrode hardly changed. The changes could be related to the loss of capacity and the amount of accumulated lead sulphate in the electrodes. In contrast, no changes in the spectra were observed in the corrosion tests. In addition, it was simulatively investigated whether the parameter determination of electrochemical processes from EIS measurements is possible for porous electrodes. With an electrical equiv [...]

Bibliographische Informationen der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek v... more Bibliographische Informationen der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Veröffentlichung in der Deutschen Nationalbiografie. Detaillierte bibliographische Daten sind im Internet unter folgender URL abrufbar: http://dnb.d-nb.de. Digitale Fassung auf den Internetseiten der Universitätsbibliothek der RWTH Die digitale Fassung dieser Dissertation ist auf den Internetseiten der Universitätsbibliothek der RWTH Aachen University unter http://publications.rwth-aachen.de abrufbar.

The state estimation for lithium-ion battery cells has been the topic of many publications concer... more The state estimation for lithium-ion battery cells has been the topic of many publications concerning the different states of a battery cell. They often focus on a battery cell’s state of charge (SOC) or state of health (SOH). Therefore this paper introduces a, on one hand, a new lithium-ion battery data set with dynamic validation data over degradation and on the other hand a model-based SOC and SOH estimation based on this dataset as a reference. An unscented Kalman filter-based approach was used for SOC estimation and extended with a holistic ageing model to handle the SOH estimation. The paper describes the dataset, the models, the parameterisation, the implementation of the state estimations, and their validation using parts of the dataset resulting in a SOC and SOH estimation over battery life. The results show that the dataset can be used to extract parameters, design models based on it and validate with dynamically degraded battery cells.

Bibliography 143 vii viii (i) measured in installed capacity (ii) The efficiency is defined as th... more Bibliography 143 vii viii (i) measured in installed capacity (ii) The efficiency is defined as the mass out over the mass in. This thesis discusses the batteries on a cell level (one positive and one negative electrode with electrolyte), a description of a full lead-acid battery can be found in e.g. [12]. The most important mechanisms for the dynamic response of lead-acid batteries are presented and the according equation systems are set up in chapter 1. To solve the resulting equation

Batteries

Lithium–ion batteries (LIBs) are used in many personal electronic devices (PED) and energy-demand... more Lithium–ion batteries (LIBs) are used in many personal electronic devices (PED) and energy-demanding applications such as electric vehicles. After their first use, rather than dispose of them for recycling, some may still have reasonable capacity and can be used in secondary applications. The current test methods to assess them are either slow, complex or expensive. The voltage integral during the constant current (CC) charge of the same model of LIBs strongly correlates with the state of health (SOH) and is faster than a full capacity check. Compared to the filtering requirement in the incremental capacity (IC) and differential voltage (DV) or the complex analysis in the electrochemical impedance spectrum (EIS), the voltage integral offers a simple integration method, just like the simple capacity Coulomb’s counter that is installed in many BMS for estimating the SOC of LIBs. By obtaining the voltage integral of a relatively new cell and an old cell of the same model with known SOH...

Energies

Realising an ideal lithium-ion battery (LIB) cell characterised by entirely homogeneous physical ... more Realising an ideal lithium-ion battery (LIB) cell characterised by entirely homogeneous physical properties poses a significant, if not an impossible, challenge in LIB production. Even the slightest deviation in a process parameter in its production leads to inhomogeneities and causes a deviation in performance parameters of LIBs within the same batch. The greater the number and/or intensity of inhomogeneities, the more they need to be avoided. Severe inhomogeneities (defects), such as metal particle contamination, significantly impact the cell’s performance. Besides electrical measurements, image-based measurement methods can be used to identify defects and, thus, ensure the production quality and safety of LIBs. While the applicability of computed tomography (CT) as an image-based measurement method for detecting defects has been proven, the limitations of this method still need to be determined. In this study, a systematic analysis of the capabilities of CT imaging was conducted....

Mtz - Motortechnische Zeitschrift, Apr 12, 2013

BATTERIESYSTEMTECHNIK gungen unabhängiger Betrieb des Fahrzeugs gewährleistet sein. Dabei muss di... more BATTERIESYSTEMTECHNIK gungen unabhängiger Betrieb des Fahrzeugs gewährleistet sein. Dabei muss die Batterieheizung sicheres Laden bei frostigen Temperaturen und die Kühlung uneingeschränkte Antriebsleistung bei sommerlicher Hitze garantieren. Mehrkosten, zusätzliches Gewicht und Bauraum müssen dabei stets gegen den Mehrwert aufwendiger Temperiersysteme abgewogen werden. Ferner kann eine unzureichend dimensionierte Kühlung in ungünstigen Fällen zu verstärkten Alterungseffekten in den Batteriezellen und damit zu einer Lebensdauerverkürzung des Systems führen. Um optimale Betriebs-und Ladestrategien implementieren zu können, ist es notwendig, das Alterungsverhalten einer Batteriezelle in allen Einzelheiten zu verstehen. Dazu müssen umfangreiche Tests bei verschiedenen Ladezuständen, Temperaturen, Entladetiefen und Stromstärken durchgeführt werden. Die Erfahrung zeigt, dass unterschiedliche Zellprodukte jeweils andere Alterungseigenschaften aufweisen.

Journal of energy storage, Oct 1, 2017

The contribution presents impedance spectra of enhanced flooded batteries (EFBs) with reference e... more The contribution presents impedance spectra of enhanced flooded batteries (EFBs) with reference electrodes for micro-hybrid applications. Batteries of different manufacturers are compared, also with respect to the temperature-dependency of their impedance spectra. Spectra fitting to suitable electrochemical equivalent circuits (EECs) allows a more thorough understanding of the physicochemical processes in these lead-acid batteries.

CRC Press eBooks, May 23, 2011

Journal of Power Sources, Jun 1, 2012

Impedance measurements of both electrodes of a flooded OEM SLI battery at various SOC and with va... more Impedance measurements of both electrodes of a flooded OEM SLI battery at various SOC and with various direct currents have been measured. For each part of the impedance spectra, an electrochemical process is proposed and implemented in a simulation model. By simulation of impedance spectroscopy, spectra of the model are obtained and compared with the measurement. In the first part, the focus was put on inductive semicircles, while in this second part, concentration limitation and its appearance in impedance spectra is investigated.

... lifetime prediction. Examples for such models are the simulation of power flow in a system wi... more ... lifetime prediction. Examples for such models are the simulation of power flow in a system with a PV generator and a battery by Zahedi [11], the simulation of a fuel cell / super capacitor hybrid vehicle by Schiffer et al. [12] and ...

Journal of Power Sources, Oct 1, 2007

Different types of commercially available electrochemical double layer capacitors (EDLCs) were an... more Different types of commercially available electrochemical double layer capacitors (EDLCs) were analysed in accelerated ageing tests by impedance spectroscopy. From these measurements the parameters of an impedance model were determined. The characteristic change of the impedance parameters is discussed and an ageing model for EDLCs is developed.

Modeling Dynamic Charge Acceptance of SLI Batteries for Micro-Hybrid Vehicles : Presentation in 1... more Modeling Dynamic Charge Acceptance of SLI Batteries for Micro-Hybrid Vehicles : Presentation in 14th European Lead Battery Conference (ELBC), Edinburgh, 2014.