Battery Cell Capacity Determination Using Multi-Point Voltage Segmentation
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Solution Overview
Problem
Existing methods for determining the capacity of high-voltage battery cells in motor vehicles are prone to measurement errors due to sensor noise, leading to inaccurate estimation of the available capacity, which is crucial for estimating the range of electric vehicles.
Innovation Solution
A method involving the measurement of at least three open circuit voltage values at different times, determination of corresponding state of charge values, calculation of charge throughput, and derivation of capacity raw values from these measurements, which are then combined to accurately determine the battery cell capacity, reducing the impact of measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pair of open circuit voltage values and current measurements is used to determine battery capacity, then the measurement process is simple and quick, but measurement errors from sensor noise significantly impact the accuracy of the capacity calculation
Solution Approach 1:
The patent divides the capacity determination process into multiple independent measurement segments. Instead of using a single measurement pair, the system performs multiple measurements at different time points (at least three open circuit voltage values at different measurement times), creating multiple capacity raw values that are then combined. This segmentation allows the system to reduce the impact of random measurement errors while maintaining a relatively simple measurement setup.
Solution Approach 2:
The patent applies partial action by using multiple measurements (excessive relative to the minimum single measurement) to improve accuracy. By taking more measurements than the theoretical minimum of one, the system obtains multiple capacity raw values that can be combined through averaging or other combination methods, thereby reducing the influence of sensor noise and measurement errors on the final capacity determination.
2Measurement precision
If multiple open circuit voltage values are measured at different times and combined to form capacity raw values, then measurement accuracy improves, but the time required for capacity determination increases
Solution Approach 1:
The patent performs preliminary measurements of open circuit voltage at multiple time points before the final capacity calculation is needed. By collecting at least three open circuit voltage values at different measurement times in advance, the system prepares multiple capacity raw values that can be quickly combined when the capacity determination is required. This preliminary action reduces the time pressure during the actual capacity determination moment.
Solution Approach 2:
The system continuously monitors open circuit voltage over time, maintaining a record of voltage values at different measurement times. This continuous measurement approach ensures that multiple data points are always available for capacity calculation, eliminating the need for separate measurement campaigns and reducing the overall time required for accurate capacity determination.
3Reliability
If at least three open circuit voltage values are measured and multiple capacity raw values are calculated and combined, then the reliability of capacity determination improves, but the complexity of the evaluation process increases
Solution Approach 1:
The evaluation process is segmented into distinct modular steps: measuring open circuit voltage at multiple time points, determining state of charge from each voltage value, calculating charge throughput between measurement points, computing individual capacity raw values, and finally combining these raw values to obtain the final capacity. This segmentation makes the complex process more manageable and systematic, improving reliability through structured multi-step evaluation.
Solution Approach 2:
The system uses feedback by combining multiple capacity raw values (derived from different measurement pairs) to produce a final capacity determination. Each capacity raw value serves as feedback that validates or adjusts the overall capacity assessment. This feedback mechanism reduces the impact of outliers or erroneous individual measurements, thereby improving the reliability of the final capacity determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more accurate and reliable estimation of battery cell capacity, enabling better forecasting of battery aging and health assessment with reduced error impact.
Implementation Method 1
at least three open circuit voltage values, measured at different measurement times, of the battery cell are received and at least three state of charge values of the battery cell are determined from the open circuit voltage values on the basis of a predetermined open circuit voltage curve that describes a relationship between the open circuit voltage and the state of charge of the battery cell
Implementation Method 2
respective charge throughput values, specific to the pairs of values, of the battery cell are determined by integrating a measured current of the battery cell over a time interval between the two measurement times of the associated open circuit voltage values
Data Source
AI summary
A method determines a capacity of a battery cell of a high-voltage battery of a motor vehicle. The method receives at least three open-circuit voltage values of the battery cell; determines state of charge values of the battery cell from the open-circuit voltage values on the basis of a predetermined open-circuit voltage curve; forms at least two pairs of values by combining in each case two of the at least three open-circuit voltage values; determines respective charge throughput values of the battery cell which are specific to the pairs of values by integrating a measured current of the battery cell over a period between two measuring times of the associated open-circuit voltage values; determines respective capacity raw values which are specific to the pairs of values on the basis of the associated charge throughput value which is specific to the pairs of values and the associated state of charge values which are specific to the pairs of values; and determines the capacity on the basis of the at least two capacity raw values which are specific to the pairs of values.