Battery Cell State of Charge Estimation

摘要

Hybrid and electric vehicles include a traction battery including many interconnected cells. Effective battery control, such as cell balancing, may rely on an accurate state of charge value for each of the cells. A method to reduce the computational effort of the state of charge calculation is developed. An accurate pack level state of charge calculation is implemented and represents the average cell state of charge. An average cell voltage is based on a pack voltage measurement. A state of charge difference is calculated for each cell based on a difference between a cell voltage and the average cell voltage. The state of charge difference utilizes the pack state of charge and a characteristic voltage and state of charge relationship for the cell. The cell state of charge is the sum of the pack state of charge and the state of charge difference.

主权项

1. A vehicle comprising:
a traction battery including a plurality of cells; and at least one controller programmed to, in response to a difference between a cell voltage and an average cell voltage, output a cell state of charge based on a voltage offset derived from the difference and relative to a reference voltage associated with a traction battery state of charge, and balance the cells according to the cell state of charge of the cells.