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Kirchheim unter Teck, Germany

Remmlinger J.,University of Ulm | Buchholz M.,University of Ulm | Soczka-Guth T.,Deutsche ACCUmotive GmbH | Dietmayer K.,University of Ulm
Journal of Power Sources

This article presents a model-based monitoring approach for the internal resistance dependent state-of-health (SOH) of a high power lithium-ion battery cell used in hybrid electric vehicles. The monitoring method requires only signals which are already available in vehicles by measurement during regular driving. As varying battery temperatures occur during vehicle operation, a monitoring method has to cover the usual operation range from 0 C to 50 C. For this, a battery cell model from the class of linear parameter-varying (LPV) models is identified from measurement data. In contrast to many publications, the proposed monitoring method is validated using cell measurement data from driving cycles. © 2012 Elsevier B.V. All rights reserved. Source

Lebiedz D.,University of Ulm | Siehr J.,Deutsche ACCUmotive GmbH
Flow, Turbulence and Combustion

Model reduction methods are relevant when the computation time of a full convection-diffusion-reaction simulation based on detailed chemical reaction mechanisms is too large. In this article, we consider a model reduction approach based on optimization of trajectories and its applicability to realistic combustion models. As many model reduction methods, it identifies points on a slow invariant manifold based on time scale separation in the dynamics of the reaction system. The numerical approximation of points on the manifold is achieved by solving a semi-infinite optimization problem, where the dynamics enter the problem as constraints. The proof of existence of a solution for an arbitrarily chosen dimension of the reduced model (slow manifold) is extended to the case of realistic combustion models including thermochemistry by considering the properties of proper maps. The model reduction approach is finally applied to two models based on realistic reaction mechanisms: ozone decomposition as a small test case and syngas combustion as a test case including all features of a detailed combustion mechanism. ©Springer Science+Business Media Dordrecht 2014. Source

Remmlinger J.,University of Ulm | Buchholz M.,University of Ulm | Meiler M.,Deutsche ACCUmotive GmbH | Bernreuter P.,Deutsche ACCUmotive GmbH | Dietmayer K.,University of Ulm
Journal of Power Sources

For reliable and safe operation of lithium-ion batteries in electric or hybrid vehicles, diagnosis of the cell degradation is necessary. This can be achieved by monitoring the increase of the internal resistance of the battery cells over the whole lifetime of the battery. In this paper, a method to identify the internal resistance in a hybrid vehicle is presented. Therefore, a special purpose model deduced from an equivalent circuit is developed. This model contains parameters depending on the degradation of the battery cell. To achieve the required robustness and stable results under these conditions, the method uses specific signal intervals occurring during normal operation of the battery in a hybrid vehicle. This identification signal has a defined timespan and occurs regularly. The identification is done on vehicle measurement data of terminal cell voltage and current collected with a usual vehicle sampling rate. Using the adapted internal resistance value in the model, a degradation index is calculated by compensating other influences, e.g. battery temperature. This task is the main challenge, as the impact of the temperature on the resistance, for example, is one order of magnitude higher than the influence of the degradation for the investigated lithium-ion cell. The developed estimation and monitoring method is validated with measurement data from single cells and shows good results and very low computational effort. © 2010 Elsevier B.V. Source

Deutsche ACCUmotive GmbH and Li Tec Battery GmbH | Date: 2013-11-13

An electrochemical energy storage device (

Andre D.,Deutsche ACCUmotive GmbH | Meiler M.,Deutsche ACCUmotive GmbH | Steiner K.,Deutsche ACCUmotive GmbH | Wimmer C.,Deutsche ACCUmotive GmbH | And 2 more authors.
Journal of Power Sources

The influence of the operation conditions temperature and state of charge (SOC) on the performance of a commercial high-power lithium-ion cell is investigated by electrochemical impedance spectroscopy. Based on the results of several preliminary tests, measurements were run covering the complete range of automotive applications. The cell impedance is presented and analyzed. A strong nonlinear temperature correlation is shown for all frequency ranges. Although the ohmic resistance is nearly unaffected by variation in SOC, the mass transport impedance reduces from 100% to 60% SOC and increases significantly again for lower SOCs. © 2011 Elsevier B.V. Source

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