@article{ZieglerOeserHeinetal., author = {Ziegler, Andreas and Oeser, David and Hein, Thiemo and Montesinos Miracle, Daniel and Ackva, Ansgar}, title = {Reducing Cell to Cell Variation of Lithium-Ion Battery Packs During Operation}, volume = {9}, doi = {10.1109/ACCESS.2021.3057125}, pages = {24994 -- 25001}, language = {en} } @article{ZieglerOeserHeinetal., author = {Ziegler, Andreas and Oeser, David and Hein, Thiemo and Montesinos Miracle, Daniel and Ackva, Ansgar}, title = {Run to Failure: Aging of Commercial Battery Cells beyond Their End of Life}, series = {Energies}, volume = {13}, journal = {Energies}, number = {8}, doi = {10.3390/en13081858}, language = {en} } @phdthesis{Oeser, author = {Oeser, David}, title = {From the production of the single cell to the end of life of the battery module: the development of parameter variation of lithium-ion cells}, editor = {Montesinos-Miracle, Daniel and Ackva, Ansgar}, publisher = {Universitat Polit{\`e}cnica de Catalunya}, doi = {10.5821/dissertation-2117-379460}, abstract = {In lithium-ion batteries, depending on the requirements, many individual cells are connected in series and parallel. Despite very similar individual cell parameters after production, they can develop differently during the subsequent ageing process due to intrinsic and extrinsic influences. A pronounced parameter variation of the assembled cells ultimately leads to a reduced utilisation of the lithium-ion battery and thus also to a reduced lifetime. The aim of this work is therefore to gain a better understanding of the origin and development of parameter variation during the ageing process. The work is divided into three major parts. At the beginning, parameters such as capacity and internal resistance of 480 brand-new cells of one production batch are recorded. The obtained values allow the calculation of the production-related parameter variation of the cells. In order to investigate the development of the parameter variation during cell ageing, numerous ageing tests are carried out in this work. These are divided into single cell tests and module tests. With the help of single cell ageing tests, the development of the parameter variation of unconnected cells is investigated. Here, several cells are combined into groups and aged under identical conditions. In order to show the influence of different operating conditions on the parameter variation during single cell ageing, the cell groups are aged at different temperatures and different load currents. Finally, by ageing various self-built modules, the development of the parameter variation of cells connected in series and in parallel is investigated. By varying the load current and the number of cells connected in parallel, further dependencies are investigated. The measured data show that both the load on the cells and the ambient temperature have a decisive influence on the development of parameter variation. Operating conditions near the lithium plating boundary are particularly problematic. Since the onset of lithium plating varies slightly between the ageing cells, there are extreme differences in the ageing rate over a certain period of time. This ultimately leads to large parameter variations in the tests carried out. The cells used in this work are cylindrical cells in 18650 format with a nominal capacity of 2.6 Ah (Samsung ICR18650-26J). The high-energy cells consist of a NMC cathode and a graphite anode.}, language = {en} } @article{OeserHeinZiegleretal., author = {Oeser, David and Hein, Thiemo and Ziegler, Andreas and Seefried, Michael and Gielinger, Sebastian and Montesinos-Miracle, Daniel and Bohn, Gunther and Ackva, Ansgar}, title = {Age-related development of cell-to-cell variation under various operating conditions in commercial NMC/graphite lithium-ion cells}, series = {Journal of Energy Storage}, volume = {101}, journal = {Journal of Energy Storage}, publisher = {Elsevier}, doi = {10.1016/j.est.2024.113787}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-57585}, pages = {10}, abstract = {In real applications, lithium-ion cells are usually used in individual interconnections, with the worst cell determining capacity, performance and service life. Due to different ageing rates of the assembled cells, cell-to-cell variation changes over lifetime. In literature, cell-to-cell variation is usually investigated near room temperature under one operating condition. Data regarding cell-to-cell variation above and below room temperature under different operating conditions are hard to find. To fill the gap in literature, this study considers cell-to-cell variation as a function of different charge/discharge currents at ambient temperatures between 0 °C and 40 °C on commercial NMC/graphite cells (Samsung SDI ICR18650-26J). The results demonstrate that cell-to-cell variation strongly depends on the selected operating conditions. In particular, operating conditions near the lithium plating boundary at the beginning of the ageing process have a particularly high risk of developing a pronounced variation. Fast charging or charging at lower temperatures should therefore be avoided. Operation at moderate temperatures and currents, on the other hand, only leads to a slight increase in cell-to-cell variation in the tests carried out. A 24-month storage during the testing period at 30\% SOC and room temperature of the same cells shows even a slight reduction in cell-to-cell variation.}, language = {en} } @article{HeinOeserZiegleretal., author = {Hein, Thiemo and Oeser, David and Ziegler, Andreas and Montesinos-Miracle, Daniel and Ackva, Ansgar}, title = {Aging Determination of Series-Connected Lithium-Ion Cells Independent of Module Design}, series = {Batteries}, volume = {9}, journal = {Batteries}, number = {3}, doi = {10.3390/batteries9030172}, abstract = {In this work, a battery consisting of eight commercial NMC/graphite cells connected in series was cycled to 60\% of its initial capacity. During the test, special care was taken to ensure that the results were not influenced by either the module assembly or the module design. For this purpose, the cells were virtually connected in a laboratory environment with the help of the test device as if they were operated together in a battery. Extrinsic influences that affect cell aging were thus reduced to a minimum. Differential Voltage Analysis (DVA), Electrochemical Impedance Spectrum (EIS), and relaxation measurements were performed to analyze the aging behavior of each cell. The results show that despite a theoretically perfect module design, Cell-to-Cell Variations (CtCV) occurred during aging. The shifting Depth of Discharge (DoD) values among the cells further amplify CtCV. Lithium plating was also observed in the faster aging cells after cyclic aging, suggesting that this aging effect contributes significantly to the development of CtCV. After the aging test, the battery was equipped with an active balancing system that maximizes capacity utilization. More important, the balancing charges which are calculated iteratively within the used balancing algorithm show a strong correlation to the pure capacity losses and thus provide a new way to determine the capacity values of each cell individually without disassembling the battery.}, language = {en} } @inproceedings{BohnTaubLinkeetal., author = {Bohn, Gunther and Taub, J. and Linke, Andreas and Bayer, Sven and Oeser, David and Ziegler, Andreas and Ettl, P. and Ackva, Ansgar}, title = {High-resolution Interferometric Measurement of Thickness Change on a Lithium-Ion Pouch Battery}, series = {3rd International Conference on Environmental and Energy Engineering (IC3E 2019)}, volume = {281}, booktitle = {3rd International Conference on Environmental and Energy Engineering (IC3E 2019)}, doi = {10.1088/1755-1315/281/1/012030}, pages = {8}, abstract = {Volume change of graphite leads to change in thickness of battery storage layers during discharging and charging. Pouch cell lithium ion batteries are used in the field of electric vehicles and solar home storage. This paper shows a measurement setup for the three-dimensional measurement of thickness change on a flat 6.7mm thick pouch cell using a white light interferometer. With a measuring field of 7.05mm diameter the resulting 3D thickness change record contains 226000 3D readings. The measuring points have a lateral distance of 13.1μm. The repeatability of the measurement is 312.8nm for the individual values and 64.1nm for the average value. In addition, this paper shows how the storage capacity of this pouch cell drops over 30 charge cycles.}, language = {en} } @article{GielingerHeinZiegleretal., author = {Gielinger, Sebastian and Hein, Thiemo and Ziegler, Andreas and Oeser, David and Breitfelder, Sebastian and Bohn, Gunther}, title = {A Short Time Expansion Measurement Method for the Detection of Aging Effect of Lithium Ion Cells Using a High Resolution Laser Interfometric Setup}, series = {IEEE Access}, volume = {11}, journal = {IEEE Access}, publisher = {IEEE}, doi = {10.1109/ACCESS.2023.3341505}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-53654}, pages = {11}, abstract = {In this work a new expansion measurement methodology for the detection of ageing mechanisms in lithium ion cells is described and evaluated. For this purpose, a polarization-optical homodyne Michelson interferometer with a resolution of approx. 10 nm was set up to allow measurements of different cell types, cell sizes, and cell chemistry within a Memmert IP55 climate chamber. The used interferometric measurement setup is ten times more accurate than measurement systems commonly used for battery measurements in the literature. The better spatial resolution of an interferometer setup enables the recording of the expansion response to short current pulses with low transferred charge. This offers the possibility to detect ageing mechanisms such as lithium plating within short measuring times. With this measurement setup, a lithium iron phosphate pouch cell from the company A123, with the model identification AMP20M1HD-A, is measured. First, an expansion measurement over a full charge and discharge cycle with a constant load of ± C 20 (b=1 A) is performed. Here, the cell undergoes an expansion of about 42 μm. Subsequently, the in this work proposed measurement methodology is presented to show the influence of effects such as the formation of overshooting graphite stages or lithium plating on cell expansion. For this purpose, at a residual capacitance of 50\%, the cell is pulsed with current of different intensity I ∈ {±20A,±80A} for t = {240 s, 60 s}, at T = {10 ◦C, 20 ◦C, 30 ◦C}, respectively, and the mechanical response is recorded using the high accuracy interferometer setup. A mechanical relaxation of the cell after the pulses with a time constant in the range between 10 s and 20 s can be observed. It is shown that this relaxation behavior can be associated with effects of the anode known from the literature, such as the formation of overshooting graphite stages or lithium plating. These effects can be recorded by the very high-resolution measurement already with little transferred charge and within a short measurement time.}, language = {en} } @article{HeinZieglerOeseretal., author = {Hein, Thiemo and Ziegler, Andreas and Oeser, David and Ackva, Ansgar}, title = {A capacity-based equalization method for aged lithium-ion batteries in electric vehicles}, series = {Electric power systems research}, volume = {191}, journal = {Electric power systems research}, issn = {0378-7796}, doi = {10.1016/j.epsr.2020.106898}, language = {en} } @inproceedings{ZieglerOeserHeinetal., author = {Ziegler, Andreas and Oeser, David and Hein, Thiemo and Ackva, Ansgar}, title = {Development and Application of an Active Balancing System for Lithium-Ion Cells}, series = {2019 IEEE Vehicle Power and Propulsion Conference (VPPC)}, booktitle = {2019 IEEE Vehicle Power and Propulsion Conference (VPPC)}, isbn = {978-1-7281-1249-7}, doi = {10.1109/VPPC46532.2019.8952317}, pages = {1 -- 6}, language = {en} } @inproceedings{ZieglerOeserArndtetal., author = {Ziegler, Andreas and Oeser, David and Arndt, Bernhard and Ackva, Ansgar}, title = {A Universal, Modular and Bidirectional Active Balancing System for Lithium-Ion Cells}, series = {Proceedings of the 10th International Scientific Symposium on Electrical Power Engineering}, booktitle = {Proceedings of the 10th International Scientific Symposium on Electrical Power Engineering}, editor = {University of Košice, Technical}, isbn = {978-80-553-3324-3}, pages = {400 -- 405}, language = {en} } @inproceedings{ZieglerOeserArndtetal., author = {Ziegler, Andreas and Oeser, David and Arndt, Bernhard and Ackva, Ansgar}, title = {Comparison of Active and Passive Balancing by a Long Term Test Including a Post-Mortem Analysis of all Single Battery Cells}, series = {2018 International IEEE Conference and Workshop in {\´O}buda on Electrical and Power Engineering (CANDO-EPE)}, booktitle = {2018 International IEEE Conference and Workshop in {\´O}buda on Electrical and Power Engineering (CANDO-EPE)}, isbn = {978-1-7281-1154-4}, doi = {10.1109/CANDO-EPE.2018.8601165}, pages = {15 -- 20}, language = {en} } @inproceedings{OeserZieglerArndtetal., author = {Oeser, David and Ziegler, Andreas and Arndt, Bernhard and Ackva, Ansgar}, title = {Effectiveness of Active Balancing on High Dispersion Batteries}, series = {2018 International IEEE Conference and Workshop in {\´O}buda on Electrical and Power Engineering (CANDO-EPE)}, booktitle = {2018 International IEEE Conference and Workshop in {\´O}buda on Electrical and Power Engineering (CANDO-EPE)}, isbn = {978-1-7281-1154-4}, doi = {10.1109/CANDO-EPE.2018.8601129}, pages = {21 -- 26}, language = {en} } @article{OeserZieglerAckva, author = {Oeser, David and Ziegler, Andreas and Ackva, Ansgar}, title = {Single cell analysis of lithium-ion e-bike batteries aged under various conditions}, series = {Journal of power sources}, volume = {397}, journal = {Journal of power sources}, issn = {0378-7753}, doi = {10.1016/j.jpowsour.2018.06.101}, pages = {25 -- 31}, language = {en} }