Secondary Battery SOH Correction via Q-dQ/dV Curve Analysis
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Solution Overview
Problem
Existing methods for estimating the state of health (SOH) of secondary batteries are unable to sufficiently reduce the error between estimated and actual SOH values during charge and discharge cycles.
Innovation Solution
A secondary battery control device and method that corrects the SOH by calculating the product of capacity between two characteristic points and the dQ/dV value at an extreme point on a Q-dQ/dV curve, using pre-determined constants A and B derived from a correction sample, to accurately reflect the battery's deterioration state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods (voltage-based dQ/dV analysis) are used to estimate SOH, then the estimation process is simple, but the error between estimated and actual SOH values is large
Solution Approach 1:
The patent transforms the SOH estimation approach by changing the parameter representation from direct voltage-based dQ/dV analysis to a corrected model using the relationship SOH_corrected = A × SOH_estimated + B. This parameter transformation allows the system to maintain simple estimation methods while achieving higher accuracy through mathematical correction of the estimated values.
Solution Approach 2:
The patent replaces complex physical measurement systems with a mathematical correction model. Instead of using more complex hardware or measurement methods to improve accuracy, the invention substitutes a computational correction approach that uses pre-determined constants A and B to adjust the estimated SOH values, thereby achieving high precision without increasing device complexity.
2Reliability
If charge and discharge cycles are repeated to monitor battery deterioration, then more data is available for analysis, but the deviation between estimated and actual SOH values increases over time
Solution Approach 1:
The patent implements a feedback mechanism where the corrected SOH values (using constants A and B) are continuously applied to update the battery state assessment. This feedback loop ensures that as more charge-discharge cycle data becomes available, the system continuously corrects the SOH estimation, maintaining reliability over time rather than allowing deviation to increase.
Solution Approach 2:
The patent performs preliminary calculation of constants A and B using data from charge-discharge cycles before applying the correction formula. By pre-determining these correction parameters, the system is ready to immediately apply corrections when needed, eliminating delays in the correction application process while still benefiting from accumulated cycle data.
Data Source
AI summary
A secondary battery control device, on a Q-dQ/dV curve, when a capacity between two characteristic points or two points mathematically equivalent thereto is represented by α, a dQ/dV value at any extreme point of a plurality of extreme points plotted on the Q-dQ/dV curve or a point mathematically equivalent thereto is represented by β, a product of the α and the β is represented by X, and constants obtained in advance from a relationship between the X in a correction sample and a deterioration degree of the correction sample are represented by A and B, a deterioration degree SOH of the secondary battery is corrected to SOH=AX+B . . . (1). A battery pack including this secondary battery control device is highly safe, contributes to the stable supply of energy and contributes to sustainable development goals.