Secondary Battery Life Evaluation with DC-IR Acceleration Factors
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Solution Overview
Problem
Existing methods for evaluating the life of secondary batteries, particularly lithium-ion batteries, are time-consuming and inefficient, making it difficult to obtain results within a short development cycle required for products like electric vehicles and energy storage systems.
Innovation Solution
A method and device that utilize inputting specific temperature, charging, and discharging rates to calculate an acceleration factor, reducing the evaluation period by using an equation that relates direct current internal resistance increase rate to capacity degradation rate, allowing for accelerated life evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional life evaluation methods are used, then measurement precision is maintained, but evaluation time becomes excessively long
Solution Approach 1:
The patent changes the evaluation parameters by using acceleration factors derived from the relationship between DC internal resistance increase rate and capacity degradation rate. By establishing that AF = DC-IR increase rate / Capacity degradation rate, the method transforms the evaluation from direct long-term aging observation to accelerated testing using measurable electrical parameters, thereby reducing evaluation time while maintaining accuracy
Solution Approach 2:
The patent introduces DC internal resistance as an intermediary parameter to evaluate battery life. Instead of directly measuring capacity degradation over long periods, the method uses DC-IR increase rate as a mediator that correlates with battery aging. This intermediary measurement enables accelerated life evaluation by providing a faster proxy indicator of battery degradation
2Productivity
If acceleration factor is increased to reduce evaluation period, then productivity improves, but reliability of evaluation may deteriorate
Solution Approach 1:
The patent implements feedback by continuously monitoring both DC internal resistance and capacity during accelerated testing. The method uses the relationship AF = DC-IR increase rate / Capacity degradation rate to dynamically adjust and validate the acceleration factor. This feedback mechanism ensures that even under accelerated conditions, the evaluation remains reliable by verifying that the correlation between DC-IR and capacity degradation holds throughout the test
Solution Approach 2:
The patent carefully controls parameter changes by establishing specific ranges for acceleration factors (3 to 8) and state of health thresholds (80% to 90%). These controlled parameter changes ensure that acceleration is sufficient to reduce evaluation time but not so extreme as to compromise the validity of the results. The method transforms evaluation conditions from conventional slow aging to controlled accelerated aging within defined parameter boundaries
Data Source
AI summary
A method for evaluating a life of a secondary battery, including an evaluation condition input process of inputting a temperature, a charging rate, and a discharging rate to evaluate the life of the secondary battery, a data computation process of computing an evaluation period, in which a state of health of the secondary battery reaches a set range, a capacity degradation rate, and a direct current internal resistance change rate, and an acceleration factor calculation process of calculating an acceleration factor of the secondary battery using a first equation, the first equation being that the acceleration factor is equal to the direct current internal resistance increase rate divided by the capacity degradation rate.