University of Toronto

Eleappower Ltd.

Zhe Gong

Olivier Trescases

When balancing cells in battery packs, the voltage induced by the balancing current across the parasitic wire resistance distorts the measured cell voltage, leading to inaccurate cell state estimation. A method and battery management system to extract a parasitic resistance of battery connection wires connecting a cell of a battery to a cell balancing circuit is disclosed. The parasitic wire resistances for a battery pack are extracted through the coordinated operation of a pack-level current source and cell-level balancing circuit. A voltage drop is imposed and measured across the parasitic resistances while maintaining zero current in the immediate battery cell. Maintaining zero current in the immediate battery cell avoids possible extraction error resulting from voltage drop across the battery cell impedance due to battery cell current flow.

Method and system for improved state estimation accuracy in battery management systems with cell balancing

The present disclosure provides electrical architecture for electrochemical impedance spectroscopy (EIS). An EIS circuit comprises at least two current regulators and an electrical energy storage device, which are connected with one or more electrochemical cells in a configuration that decouples power flowing into the respective current regulators. The presence of the electrical energy storage device enables each regulator to operate simultaneously at lower power levels while inducing the desired EIS perturbation current. Operation at low power allows lower volume and cost for the same current compared to only dissipative or non-dissipative current regulators. Further, the electrical energy storage device allows the power flowing through the current regulators to be varied independently in order to achieve the desired EIS perturbation current while a minimum amount of heat is generated in the circuit, thus allowing the circuit to occupy minimal size and incur minimal cost.

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Toronto, Canada

Zhe Gong