Traction Battery Age Indication via Statistical Capacity Ratio
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Solution Overview
Problem
Existing methods for estimating the age of traction batteries in hybrid and electric vehicles are prone to fluctuations due to variations in environmental conditions and measurement errors, making them unsuitable for reliable age indication.
Innovation Solution
A system that calculates the age of a traction battery by using a ratio of a reference amp-hour value, derived from the mean and standard deviation of historical amp-hour values, to determine a battery age state, which is displayed on an instrument cluster and used to operate the battery accordingly, with discrete states indicating new, mid-life, and end-of-life conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods are used to estimate battery age, then the estimation process is simple, but the reliability of the age indication deteriorates due to fluctuations from environmental conditions and measurement errors
Solution Approach 1:
The system continuously monitors amp-hour values over time and uses this feedback to update the statistical parameters (mean and standard deviation). This continuous feedback loop allows the system to adapt to changing conditions and improve the reliability of age indication while maintaining a manageable level of complexity through automated updates.
Solution Approach 2:
The invention changes from using single-point measurements to using statistical parameters (mean and standard deviation) derived from multiple historical measurements. This parameter transformation allows the system to account for environmental variations and measurement errors, significantly improving reliability. The age estimation is then based on how the mean amp-hour value deviates from the beginning-of-life value, providing a more robust indicator.
2Measurement precision
If statistical methods are used to derive reference amp-hour values, then measurement precision improves, but the complexity of calculation increases
Solution Approach 1:
The system performs preliminary statistical processing by continuously maintaining the mean and standard deviation of historical amp-hour values in memory. This preliminary action ensures that when age estimation is needed, the calculations are already prepared and can be performed quickly using simple comparisons against beginning-of-life values, thus improving precision without significantly increasing operational complexity.
Solution Approach 2:
The system automatically updates its own statistical parameters (mean and standard deviation) using newly measured amp-hour values without requiring external intervention. This self-service approach allows the system to maintain high measurement precision through continuous statistical refinement while keeping the computational complexity manageable through automated, routine calculations.
Data Source
AI summary
A vehicle includes a traction battery and a controller. The controller is programmed to output an age value of the traction battery based on a ratio of a reference capacity value to an initial reference capacity. The reference capacity value is derived from a mean and a standard deviation of a plurality of historical battery capacity values and has a predetermined probability of being less than an actual battery capacity. The controller is programmed to adjust a battery control strategy based on the age value. The vehicle includes an instrument cluster that is configured to display the age value.