Battery Cell Capacity Estimation from Charge-Discharge Curve Patterns
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Solution Overview
Problem
Existing battery modules composed of multiple cells in series have inaccurate capacity determination due to voltage deviation and deterioration, making it difficult to assess the individual cell capacities accurately.
Innovation Solution
An apparatus and method for calculating battery cell capacity by deriving discharge and charge curves for each cell, extending these curves based on the most deteriorated cell, and calculating additional capacities using charge-discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery capacity is determined based on the most deteriorated cell in a series-connected module, then the module's reliability is maintained, but the measurement precision of individual cell capacities deteriorates
Solution Approach 1:
The patent divides the battery module into individual cell segments and applies separate capacity estimation procedures to each cell. By segmenting the measurement process, the system can determine individual cell capacities while still ensuring module reliability through comprehensive monitoring of all cells, not just the most deteriorated one.
Solution Approach 2:
The patent changes the measurement parameters by using multiple charge-discharge cycles with varying rates (C-rates) and temperatures. This allows the system to capture different aspects of cell behavior and estimate individual capacities more accurately, resolving the contradiction between maintaining module reliability and measuring individual cell precision.
2Measurement precision
If charge-discharge cycles are performed to measure cell capacity, then the capacity measurement accuracy improves, but the time required for measurement increases
Solution Approach 1:
The patent performs preliminary charge-discharge cycles at standardized conditions to establish baseline characteristics for each cell before the actual capacity measurement. This preliminary action allows the system to predict individual cell capacities more quickly, reducing the time required for accurate measurement while maintaining precision.
Solution Approach 2:
The patent uses multiple charge-discharge cycles with different C-rates (including excessive discharge rates beyond normal operating conditions). By performing these partial or excessive actions, the system gathers sufficient data to accurately estimate capacity without requiring complete exhaustive testing, thus balancing measurement accuracy with time efficiency.
3Measurement precision
If multiple charge-discharge cycles are performed at different rates to estimate capacity, then the capacity estimation accuracy improves, but the complexity of the measurement procedure increases
Solution Approach 1:
The patent systematically changes measurement parameters (C-rates, temperatures, rest periods) according to a predefined protocol. By standardizing these parameter changes, the system achieves high capacity estimation accuracy while managing procedure complexity through structured, repeatable measurement sequences that can be automated.
Solution Approach 2:
The patent incorporates feedback mechanisms where measurement results from previous cycles inform subsequent measurement conditions. This feedback loop allows the system to adaptively refine capacity estimates based on observed cell behavior, improving accuracy while the automated feedback process manages complexity by reducing the need for manual intervention in the multi-cycle procedure.
Data Source
AI summary
A method for estimating battery cell capacity may comprise deriving a discharge curve for each battery cell included in a module including a plurality of battery cells; deriving a charge curve for each battery cell included in the module; calculating an additional dischargeable capacity of a second battery cell based on a pattern of the discharge curve of a first battery cell; calculating an additional chargeable capacity of the second battery cell based on the transition of the charge curve of the first battery cell; and calculating a capacity of the second battery cell based on the additional dischargeable capacity and the additional chargeable capacity of the second battery cell.