Battery SOH Estimation Using Fast-Slow Discharge Correlation
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Solution Overview
Problem
The existing methods for diagnosing electrochemical cell performance losses over time are inefficient and costly, as they require lengthy standard tests under weak current, making it difficult to quantify degradation and determine the state of health (SOH) accurately, especially when usage conditions are unknown.
Innovation Solution
A method involving a measurement phase with training and characterization sequences, and an aging phase, to create a chart of correlations between rapid and slow discharges, allowing for the measurement of wear and state of health by comparing discharge times and currents, enabling faster and more cost-effective assessment of cell health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard slow discharge testing is used to measure cell capacity, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The method performs preliminary characterization tests during manufacturing to establish correlation data between fast and slow discharge capacities. This pre-established correlation chart allows rapid assessment of used cells without performing lengthy slow discharge tests, thus resolving the time-precision contradiction by preparing reference data in advance.
Solution Approach 2:
The invention introduces an intermediary correlation chart that relates fast discharge capacity to slow discharge capacity. This chart acts as a mediator, allowing the system to infer accurate slow discharge capacity (the precise measurement) from fast discharge measurements (the quick test), thereby resolving the contradiction between measurement precision and time loss.
2Loss of time
If fast discharge testing is used to reduce measurement time, then loss of time is reduced, but measurement precision deteriorates due to parasitic effects
Solution Approach 1:
The correlation chart serves as an intermediary that translates fast discharge measurements into accurate slow discharge capacity estimates. The chart encapsulates the relationship between fast and slow discharge behaviors, allowing the system to use quick tests while obtaining precision-equivalent results through the mediating correlation data.
Solution Approach 2:
The method creates a copy of the slow discharge capacity information through the correlation chart. Instead of directly measuring slow discharge capacity (which takes time), the system measures fast discharge capacity and uses the pre-established correlation to obtain a copied representation of the slow discharge capacity, achieving both speed and accuracy.
3Measurement precision
If dismantling batteries for direct measurement is performed, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The battery cells perform self-characterization during the manufacturing process when they are still accessible and can be easily tested. The correlation data is generated by the cells themselves under controlled conditions, eliminating the need for complex dismantling equipment and procedures later when assessing used cells.
Solution Approach 2:
All necessary characterization and correlation establishment is performed preliminarily during manufacturing before the cells are deployed. This preliminary action eliminates the need for complex dismantling and measurement systems later, as the correlation chart already contains all necessary information for rapid assessment.
4Loss of time
If non-standard fast discharge indicators are created, then loss of time is reduced, but reliability decreases due to lack of comparability
Solution Approach 1:
The correlation chart acts as an intermediary that ensures results remain comparable to standard tests. By using the chart to translate fast discharge measurements into slow discharge capacity equivalents, the system maintains compatibility with standard testing frameworks while achieving rapid assessment, thus preserving both speed and reliability.
Solution Approach 2:
The correlation chart provides a universal translation mechanism that works across different cell types and conditions. It enables the fast discharge test to serve multiple functions: rapid assessment, accurate capacity determination, and standard-compliant result generation, thereby achieving both time reduction and result comparability.
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 significantly reduces the time required to measure residual capacity from three hours to less than 30 minutes, providing reliable and rapid health assessments of electrochemical cells, eliminating the need for costly dismantling and ensuring results are comparable to standard tests.
Implementation Method 1
The invention relates to the field of batteries, and more particularly to the diagnosis of electrochemical cells, or accumulators
Implementation Method 2
relaxing the at least one cell for a first duration; relaxing the at least one cell for a second duration
Data Source
AI summary
A method of constructing a chart of correlations between a rapid discharge and a slow discharge in order to measure the wear of at least one electrochemical cell, including a measurement phase that includes a training sequence followed by a characterization sequence, and an aging phase. Each of the sequences includes charging-relaxing-discharging-relaxing under controlled conditions and is repeated with different conditions. The time of each discharge is measured. The aging phase includes an alternation of charges and discharges with no intermediate relaxation and is implemented before each repetition of the measurement phase, such that a real capacity is obtained for a plurality of pairs of imposed parameters.