High Voltage Battery Cell Balancing via EMF Discrimination
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Solution Overview
Problem
Existing cell balancing methods for high-voltage battery packs face challenges in accurately controlling electromotive force due to influences from IR voltage and polarization voltage, leading to incorrect balancing and potential loss of electromotive force.
Innovation Solution
A method that measures the electromotive force of each cell by discriminating between zero current and low current states to accurately determine the cell electromotive force, computes the total amount of charges needed for balancing, and completes balancing when the accumulative charges match the total, thereby avoiding errors from IR and polarization voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If real-time voltage measurement is used for cell balancing control, then the balancing operation can be performed based on voltage feedback, but the measurement is influenced by IR voltage and polarization voltage leading to incorrect electromotive force determination
Solution Approach 1:
The patent applies preliminary action by performing current interruption before voltage measurement. The control unit interrupts the current flowing through the battery cell immediately before measuring the terminal voltage, ensuring that IR voltage and polarization voltage effects are eliminated. This timing-based approach allows accurate electromotive force measurement without requiring complex compensation algorithms.
Solution Approach 2:
The patent extracts the disturbing factors (IR voltage and polarization voltage) from the measurement system by interrupting the current flow. By separating the current interruption step from the voltage measurement step, the method isolates the electromotive force measurement from the harmful voltage drops and polarization effects that occur during current flow.
2Productivity
If cell balancing is performed based on terminal voltage during current flow, then balancing operation can be executed in real-time, but the electromotive force measurement becomes inaccurate due to IR voltage and polarization voltage influences
Solution Approach 1:
The patent applies periodic action by implementing cyclic current interruption and voltage measurement sequences. The control unit periodically interrupts the current flow and measures the terminal voltage at these interruption moments, then uses these measurements for balancing control decisions. This periodic sampling approach maintains real-time balancing capability while ensuring accurate electromotive force measurements at each sampling point.
3Duration of action of moving object
If current is continuously flowing through the battery cell during balancing, then the balancing operation can be performed without interruption, but the terminal voltage measurement includes errors from IR voltage and polarization voltage
Solution Approach 1:
The patent applies preliminary action by preparing the measurement condition (current interruption) before the actual voltage measurement. The control unit is configured to interrupt current flow as a preliminary step immediately preceding the voltage measurement, ensuring that the measurement is taken under ideal conditions without IR voltage or polarization voltage contamination.
Data Source
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AI summary
The present invention relates to a cell balancing method for a high- voltage battery pack, and the method comprises steps of a) measuring an electromotive force of each cell composing the battery pack; b) selecting the cell to be balanced based on the electromotive force of the each cell; c) computing a total amount of charges used for balancing of the cell to be balanced; d) obtaining an accumulative amount of charges by accumulating an amount of current consumed for the balancing while performing the balancing of the cell to be balanced; and e) completing the balancing of the cell to be balanced when the accumulative amount of charges equals the total amount of charges.