Electrochemical Cell State of Health Estimation via Linear Voltage Approximation
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Solution Overview
Problem
Existing methods for estimating the state of health of electrochemical cells, such as lithium-ion batteries, face inaccuracies due to imprecise voltage measurements, especially in the presence of transient noises, which can impact the estimation of internal resistance and overall battery performance.
Innovation Solution
A method that applies a current peak to the cell, measures voltage variations over time, and calculates coefficients for linear approximation of voltage changes, allowing for precise estimation of state of health by comparing calculated coefficients to initial values and referencing aging tables, indicating degradation and ability to deliver power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurement is performed to estimate internal resistance and SOH, then SOH estimation can be obtained, but measurement accuracy deteriorates due to transient noise affecting voltage measurements
Solution Approach 1:
The patent applies preliminary action by performing linearization of the voltage-time relationship before using it for SOH estimation. The method pre-processes the voltage measurement data through linear approximation techniques, establishing a linearized voltage model in advance that compensates for transient noise effects before the actual SOH calculation occurs.
Solution Approach 2:
The patent introduces an intermediary approach by using linearized voltage coefficients as a mediator between raw voltage measurements and SOH estimation. Instead of directly using noisy voltage measurements, the method introduces linearized coefficients (slope and intercept from linear approximation) that filter out transient noise while preserving the underlying degradation trend information.
2Measurement precision
If current peak is applied to the cell to measure voltage variation, then internal resistance can be estimated, but measurement complexity increases due to the need for precise timing and control
Solution Approach 1:
The patent applies parameter changes by transforming the measurement approach from direct voltage measurement to linearized voltage-time relationship analysis. Instead of measuring absolute voltage values at specific moments, the method changes the parameter being measured to the slope and intercept of the linearized voltage decay curve, which are more robust to timing variations and transient noise.
Solution Approach 2:
The patent substitutes a mechanical/timing-based measurement system with a mathematical modeling approach. Rather than relying on precise mechanical timing and control of current peaks, the method uses mathematical linearization techniques to extract meaningful parameters from the voltage response, reducing the need for complex hardware timing synchronization.
3Ease of manufacture
If traditional voltage measurement methods are used, then equipment cost is lower, but measurement accuracy deteriorates in the presence of transient noise
Solution Approach 1:
The patent creates a simplified mathematical model (linear approximation) that copies the essential behavior of the voltage decay process without requiring complex measurement hardware. By creating this simplified mathematical representation of the voltage-time relationship, the method achieves high measurement accuracy using standard, low-cost voltage sensors and processing units already present in typical battery management systems.
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 method provides accurate and reliable estimation of battery health, enabling effective monitoring of performance and safety by linearizing internal resistance measurements and requiring only a software update to existing devices, thus reducing deployment costs.
Implementation Method 1
the internal resistance of a battery characterizes the change in voltage (U) across the battery terminals for a given change in current (I) through the battery
Data Source
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AI summary
The present invention relates to a method for estimating the state of health of an electrochemical cell for storing electrical energy, comprising a step of applying at least one current strength peak to the cell, the current peak passing through the cell, a step of measuring the variation, as a function of the time t elapsed after the application of the current peak, of voltage U at the terminals of the cell, and a step of calculating at least one coefficient α and at least one coefficient U0, I , such that the function √t→α I χ √t +U0, I is a linear approximation of the variation of the voltage U as a function of √t for √t ≥ C, where C > o. The invention is used in electrical or hybrid vehicles.