Date of Award


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Degree Name



Electrical and Computer Engineering


batteries, Capacity Estimation, Characterization, Fast Charge, li-ion;overcharging


Balakumar Balasingam



Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


This thesis considers the problem of open circuit voltage (OCV) to state of charge (SOC) characterization in li-ion batteries for battery reuse applications. The traditional approach to OCV-SOC characterization is done by collecting voltage and current data through a slow discharge and charge process; this process usually takes about 60 hours. Such OCV-SOC characterization is performed on a few sample batteries because the OCV-SOC characterization is considered to be the same for new batteries coming out of the same manufacturing process. However, the characteristics of a battery may change as it is used for years in different environmental and usage conditions. Hence, they may need to be re-characterized before secondary use. Unlike primary characterization, the secondary characterization may have to be done faster in order to save time and cost. This thesis presents a faster approach for OCV-SOC characterization. The proposed approach in this thesis consists of constant-current profiles that halves in magnitude after a specified time. Such reductions allows us to fully deplete the battery; similarly, the battery is charged back with a reducing current profile in order to make sure the battery is fully charged. The resulting current profile reduces the total characterization time by 1/5. Secondly, we explore the idea of discharge and charge capacity of batteries. A traditional low-rate-OCV test consists of constant-current charging which results in a voltage drop based on the internal resistance and charging/discharging current. This thesis presents an approach to counteract this voltage drop, by appropriately over-charging and over-discharging the battery to obtain the most accurate representation of the capacity of the battery.

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