Online Estimation of Current-Dependent Non-Linear Battery ECM Parameters

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Solution Overview

Problem

Existing methods for modeling battery equivalent circuit models are inadequate as they fail to accurately estimate current-dependent non-linear parameters, especially under varying load conditions, leading to inefficiencies in fuel-gauging and power management.

Innovation Solution

A method and system for estimating current-dependent non-linear equivalent circuit model (ECM) parameters by measuring battery voltage and current, deriving linear ECM parameters, tracking impedance and open circuit voltage, detecting high current events, and deriving non-linear online ECM parameters using linear parameters and impedance deviations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If offline characterization is used to measure impedance across frequency range, then comprehensive battery model parameters can be obtained, but it is time-consuming and computationally expensive

Engineering Contradiction:

Improvebattery model parameter accuracyVSAvoidcharacterization time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system uses the battery's own operational current as the stimulus signal for parameter estimation, eliminating the need for external characterization equipment and offline testing. The battery serves its own characterization needs during normal operation, turning operational data into model refinement opportunities without requiring separate measurement sessions.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Parameter estimation occurs continuously during battery operation rather than in discrete offline sessions. The system continuously monitors voltage and current, and continuously updates model parameters, transforming the intermittent offline characterization process into an ongoing real-time adaptation that occurs throughout the battery's operational life.

Inventive Principle:

Principle #20Continuity of useful action

2Productivity

If system load current is used for in-situ characterization, then time-consuming offline measurement is avoided, but the current may not contain spectrally-rich content needed for accurate estimation

Engineering Contradiction:

Improvecharacterization speedVSAvoidparameter estimation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts the stimulus current to ensure spectrally-rich content is present during characterization. When the natural load current lacks sufficient spectral content, the system modifies the current profile to include appropriate frequency components, transforming a static characterization approach into an adaptive dynamic process that ensures measurement quality.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the electrical parameters of the stimulus current (amplitude, frequency content, duration) to optimize the excitation signal for parameter estimation. By adjusting current characteristics based on spectral content analysis, the system ensures that sufficient information is present in the measurements to accurately estimate all model parameters.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If linear ECM parameters are used to model battery, then computational complexity is reduced, but current-dependent non-linearities cannot be captured

Engineering Contradiction:

Improvemodel complexityVSAvoidmodel accuracy under varying current

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The model parameters are segmented into multiple sets corresponding to different current amplitude ranges. Instead of using a single linear model, the system divides the operating range into segments and selects appropriate parameter sets based on the current level, allowing the model to adapt to non-linear behavior across different operating conditions while maintaining computational efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The model transitions from a static linear parameter set to dynamic parameters that change with operating conditions. The system continuously monitors current amplitude and adjusts model parameters in real-time based on the current operating point, enabling the model to capture non-linear effects while maintaining the simplicity of linear estimation techniques at each instantaneous operating point.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250180651A1Online estimation of current-dependent non-linear equivalent circuit model parameters of a battery

Publication Date: 2025.06.05 CIRRUS LOGIC INT SEMICON LTD

AI summary

A method for estimating current-dependent non-linear equivalent circuit model (ECM) parameters of a battery may include measuring a battery voltage across terminals of the battery and a battery current drawn from the battery, deriving linear ECM parameters for modeling a linear ECM of the battery with multiple resistive-capacitive elements with different time constants to characterize temporal behaviors of the battery, continuously tracking an impedance for each of the multiple resistive-capacitive elements and an open circuit voltage of the battery, continuously monitoring the battery current to detect high current events, continuously tracking a deviation for each of the multiple resistive-capacitive elements during the high current events, and deriving non-linear online ECM parameters based on the linear ECM parameters and the deviations for the multiple resistive-capacitive elements during the high current events.