Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.800079
Title: Mathematical modelling of lead-acid batteries
Author: Sulzer, Valentin
ISNI:       0000 0004 8507 3785
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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Abstract:
Electrochemical and equivalent-circuit modelling are the two most popular approaches to battery simulation, but the former is computationally expensive and the latter provides limited physical insight. A theoretical middle ground would be useful to support battery management, online diagnostics, and cell design. In this thesis, we present a porous-electrode model of a lead-acid battery, which includes an extension of concentrated-solution theory that accounts for excluded-volume effects, local pressure variation, and a detailed microscopic water balance. Asymptotic analysis of the one-dimensional model in the limit of small discharge rate produces three reduced-order models, which relate the electrical behaviour to microscopic material properties, but simulate discharge at speeds approaching an equivalent circuit. A lumped-parameter model, which neglects spatial property variations, proves accurate for small discharge rates (below 0.1C), while a spatially resolved higher-order solution retains accuracy at higher discharge rates (up to 5C). The reduced-order models provide improved insight into the battery's behaviour. The models are fit to experimental data, showing good agreement. We then consider the three-dimensional model and exploit the limit of small aspect ratio to decompose the through-cell and transverse dimensions. Further asymptotic analyses in the limit of high conductivity and/or small discharge rate give new simplified models that capture transverse non-uniformities at reduced computational cost. In the simplest case, the current collectors act as series resistors. In order to explore the behaviour of a lead-acid battery during recharge, we return to a one-dimensional model and add an oxygen reaction to the model. We find that the oxygen recombination must be diffusion limited in the negative electrode, leading to non-monotonic voltage increase during constant-current recharge. Reduced-order models in the limit of slow recharge provide good approximations to the full charging model.
Supervisor: Howey, David A. ; Monroe, Charles W. ; Please, Colin P. ; Chapman, S. Jon Sponsor: BBOXX Ltd ; Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.800079  DOI: Not available
Keywords: Electrochemistry ; Applied mathematics
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