Calculating Available Charge and Energy of Lithium-Ion Cells Based on OCV and Internal Resistance

The design and operation of performant and safe electric vehicles depend on precise knowledge of the behavior of their electrochemical energy storage systems. The performance of the battery management systems often relies on the discrete-time battery models, which can correctly emulate the battery c...

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Bibliographic Details
Published in:Energies (Basel) 2022-11, Vol.15 (21), p.7902
Main Authors: Steger, Fabian, Krogh, Jonathan, Meegahapola, Lasantha, Schweiger, Hans-Georg
Format: Article
Language:English
Subjects:
Batteries
battery management system
Electric cells
Electric charge and distribution
Electric vehicles
Electrochemistry
Energy
Energy charge
energy content
Energy storage
Experiments
Lithium
Lithium cells
Lithium-ion batteries
mathematical model
Open circuit voltage
Parameter estimation
Peukert exponent
Power management
state-of-charge
Storage systems
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Summary:The design and operation of performant and safe electric vehicles depend on precise knowledge of the behavior of their electrochemical energy storage systems. The performance of the battery management systems often relies on the discrete-time battery models, which can correctly emulate the battery characteristics. Among the available methods, electric circuit-based equations have shown to be especially useful in describing the electrical characteristics of batteries. To overcome the existing drawbacks, such as discrete-time simulations for parameter estimation and the usage of look-up tables, a set of equations has been developed in this study that solely relies on the open-circuit voltage and the internal resistance of a battery. The parameters can be obtained from typical cell datasheets or can be easily extracted via standard measurements. The proposed equations allow for the direct analytical determination of available discharge capacity and the available energy content depending on the discharge current, as well as the Peukert exponent. The fidelity of the proposed system was validated experimentally using 18650 NMC and LFP lithium-ion cells, and the results are in close agreement with the datasheet.
ISSN:1996-1073
1996-1073
DOI:10.3390/en15217902