Estimation Device for Energy Storage Capacity
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Solution Overview
Problem
Existing methods for estimating the actual capacity of energy storage devices, such as lithium ion secondary batteries, require complex arithmetic operations and are inefficient due to the need for square-root calculations and handling of capacity change curves over time and temperature.
Innovation Solution
An estimation device and method that approximates capacity change curves using multiple straight lines, allowing for simpler arithmetic operations and reduced data storage by dividing curves into areas and using gradient maps to calculate actual capacity reduction over time and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If square-root calculation is used to estimate actual capacity based on square-root law, then estimation accuracy is improved, but arithmetic operation load becomes large and device complexity increases
Solution Approach 1:
The patent transforms the estimation approach by changing the mathematical parameters from square-root calculations to logarithmic calculations. Specifically, it uses the relationship between logarithm of capacity ratio and logarithm of time ratio, which can be computed more efficiently than square-root operations while maintaining estimation accuracy.
Solution Approach 2:
The patent replaces the mathematical computation mechanism (square-root calculation) with an alternative computational approach (logarithmic calculation combined with pre-stored reference data). This substitution reduces the arithmetic operation load by avoiding complex real-time square-root computations.
2Measurement precision
If capacity change curves are stored for multiple temperatures and time periods, then estimation accuracy is improved, but data storage requirements increase
Solution Approach 1:
The patent segments the capacity change data by dividing it into temperature-specific datasets and time-period-specific datasets. Instead of storing complete capacity change curves for all temperatures and times, it stores segmented reference values that can be combined during estimation, reducing overall storage requirements while maintaining accuracy.
Solution Approach 2:
The patent transforms the storage approach by changing from storing two-dimensional capacity-time curves for multiple temperatures to storing one-dimensional reference data that can be indexed by temperature and time. This dimensional transformation reduces storage requirements by exploiting the mathematical relationships between temperature, time, and capacity.
Data Source
AI summary
Provided is an estimation device for estimating an actual capacity of an energy storage device or a total reduction amount of the actual capacity. The estimation device includes a processor which is configured to calculate the actual capacity of the energy storage device or the total reduction amount of the actual capacity based on approximation data where a capacity change curve indicative of a transition of the actual capacity or a transition of the total reduction amount of the actual capacity with respect to an elapsed time is approximated by a plurality of straight lines.