TY - JOUR A1 - Ziegler, Andreas A1 - Oeser, David A1 - Hein, Thiemo A1 - Montesinos Miracle, Daniel A1 - Ackva, Ansgar T1 - Reducing Cell to Cell Variation of Lithium-Ion Battery Packs During Operation Y1 - 2021 U6 - https://doi.org/10.1109/ACCESS.2021.3057125 VL - 9 SP - 24994 EP - 25001 ER - TY - JOUR A1 - Ziegler, Andreas A1 - Oeser, David A1 - Hein, Thiemo A1 - Montesinos Miracle, Daniel A1 - Ackva, Ansgar T1 - Run to Failure: Aging of Commercial Battery Cells beyond Their End of Life JF - Energies Y1 - 2020 U6 - https://doi.org/10.3390/en13081858 VL - 13 IS - 8 ER - TY - JOUR A1 - Oeser, David A1 - Hein, Thiemo A1 - Ziegler, Andreas A1 - Seefried, Michael A1 - Gielinger, Sebastian A1 - Montesinos-Miracle, Daniel A1 - Bohn, Gunther A1 - Ackva, Ansgar T1 - Age-related development of cell-to-cell variation under various operating conditions in commercial NMC/graphite lithium-ion cells JF - Journal of Energy Storage N2 - 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. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-57585 VL - 101 PB - Elsevier ER - TY - JOUR A1 - Hein, Thiemo A1 - Oeser, David A1 - Ziegler, Andreas A1 - Montesinos-Miracle, Daniel A1 - Ackva, Ansgar T1 - Aging Determination of Series-Connected Lithium-Ion Cells Independent of Module Design JF - Batteries N2 - 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. Y1 - 2023 U6 - https://doi.org/10.3390/batteries9030172 VL - 9 IS - 3 ER - TY - JOUR A1 - Gielinger, Sebastian A1 - Hein, Thiemo A1 - Ziegler, Andreas A1 - Oeser, David A1 - Breitfelder, Sebastian A1 - Bohn, Gunther T1 - A Short Time Expansion Measurement Method for the Detection of Aging Effect of Lithium Ion Cells Using a High Resolution Laser Interfometric Setup JF - IEEE Access N2 - 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. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:863-opus-53654 VL - 11 PB - IEEE ER - TY - JOUR A1 - Hein, Thiemo A1 - Ziegler, Andreas A1 - Oeser, David A1 - Ackva, Ansgar T1 - A capacity-based equalization method for aged lithium-ion batteries in electric vehicles JF - Electric power systems research Y1 - 2021 U6 - https://doi.org/10.1016/j.epsr.2020.106898 SN - 0378-7796 VL - 191 ER - TY - JOUR A1 - Oeser, David A1 - Ziegler, Andreas A1 - Ackva, Ansgar T1 - Single cell analysis of lithium-ion e-bike batteries aged under various conditions JF - Journal of power sources Y1 - 2018 U6 - https://doi.org/10.1016/j.jpowsour.2018.06.101 SN - 0378-7753 VL - 397 SP - 25 EP - 31 ER -