Battery State of Health Determination via Minimization Loop
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Solution Overview
Problem
Existing methods for determining the State of Health (SOH) of batteries are inaccurate due to reliance on homogeneous aging assumptions and require specific user actions or current pulses, leading to inconsistencies in State of Charge (SOC) calculations.
Innovation Solution
A method that measures voltage, current, and cumulative capacity samples to calculate the state of health related to resistance (SOHR) and capacity (SOHC) without requiring user intervention, using a minimization loop to adjust current values and minimize differences between estimated and theoretical SOC values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static method with homogeneous aging assumption is used to determine SOH, then the determination process is simple, but the accuracy of SOH determination deteriorates due to non-homogeneous aging in real batteries
Solution Approach 1:
The patent segments the battery into multiple accumulators and further divides each accumulator's aging characteristics into separate parameters (SOHR for resistance-related aging and SOHC for capacity-related aging). This segmentation allows the system to capture non-homogeneous aging patterns across different battery components without requiring overly complex measurement systems, thus resolving the contradiction between simplicity and accuracy.
Solution Approach 2:
The patent introduces two distinct state of health parameters (SOHR and SOHC) to replace the single SOH parameter used in traditional methods. By changing from one parameter to two parameters with different physical meanings, the system can accurately represent non-homogeneous aging while maintaining a relatively simple determination process based on voltage, current, and temperature measurements.
2Measurement precision
If dynamic method using current pulses is used to determine SOH, then the accuracy of resistance measurement improves, but the ease of operation deteriorates due to requirement of specific user actions
Solution Approach 1:
The patent enables the battery management system to automatically perform resistance measurements using existing charge/discharge currents without requiring external current pulses or specific user actions. The system uses the naturally occurring currents during normal battery operation to determine SOHR, thus maintaining high measurement accuracy while significantly improving ease of operation.
Solution Approach 2:
The patent continuously determines resistance parameters during normal charge/discharge operations rather than requiring intermittent pulse tests. By utilizing the continuous flow of current during normal battery usage, the system maintains accurate resistance measurements without interrupting battery operation or requiring specific user actions, thereby resolving the contradiction between precision and ease of operation.
3Productivity
If SOC is determined using predictive models, then the productivity of battery management is improved, but the reliability deteriorates due to model accuracy assumptions and potential circuit faults
Solution Approach 1:
The patent implements a feedback mechanism where the determined SOHR and SOHC parameters are continuously used to update and refine SOC calculations. The system compares predicted SOC with actual measurements and uses the feedback to correct deviations, thereby maintaining high productivity while significantly improving the reliability of SOC determination by accounting for actual aging conditions rather than relying solely on model assumptions.
Data Source
AI summary
The invention relates to a method for determining the value of one or more parameters relating to the state of health of at least one accumulator of a battery that is intended to provide electrical energy to an external application, an electronic battery management system implementing this method, and a battery provided with this system. The method comprises the steps consisting in particular in: making a series of measurements of N samples, where N≥3, of at least the voltage, the current and the cumulative capacitance, at the terminals of said accumulator, when charging or discharging said accumulator; —creating a minimization loop by varying a current value of the first parameter of the accumulator from a determined initial value, comprising the following steps: (i) calculating N estimated values of a second parameter linked to the state of charge of the accumulator from the current value of the first parameter and said N samples, respectively (ii) calculating N theoretical values of the second parameter (iii) varying the current value of the first parameter, repeating the preceding calculation steps for each variation of said current value of the first parameter, and determining the value of the first parameter as being the current value of the first parameter that minimizes the difference between the estimated values and the theoretical values of the second parameter.