A Battery Management System with Individual Cell Equalizers and State of Charge Observers

Cell-to-cell variations in a battery pack result in an imbalance in voltage and stored charge among the cells in the pack. Using standard charging methods, these imbalances reduce the capacity and the life of the battery pack. The battery management system described here uses individual cell equalizers and state of charge (SOC) observers to achieve balance in terms of voltage and stored charge among the cells in a battery pack of lithiumion cells. A mathematical model for the lithium-ion cells has been developed that can be used as an SOC observer to track and estimate the SOC.

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