Battery Equivalent Circuit Estimation Using Sub-Band Decomposition

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Solution Overview

Problem

Existing methods for modeling battery equivalent circuit models are inefficient and require computationally expensive offline characterization, and system load current often lacks spectrally-rich content needed for accurate parameter estimation.

Innovation Solution

The method involves decomposing battery voltage and current into sub-bands based on time constants, estimating equivalent resistance and open circuit voltage for each sub-band, and generating augmented current stimulus to ensure sufficient spectral content for accurate model parameter estimation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If offline characterization measuring impedance across frequency range is used, then accurate equivalent circuit model parameters are obtained, but time-consuming and computationally expensive processes are required

Engineering Contradiction:

Improveaccuracy of equivalent circuit model parametersVSAvoidtime required for characterization

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the impedance spectrum into multiple frequency sub-bands, with each sub-band corresponding to a specific time constant of the battery. By decomposing the continuous frequency range into discrete segments, the system can efficiently estimate parameters for each RC pair independently, reducing computational complexity while maintaining accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic stimulus generation that adapts to the battery's real-time state. The stimulus signal is dynamically adjusted based on the battery's impedance characteristics and state of charge, enabling accurate parameter estimation during normal operation without requiring static offline measurements.

Inventive Principle:

Principle #15Dynamics

2Productivity

If system load current is used for in-situ characterization, then time-consuming offline characterization is avoided, but spectrally-rich content may not be sufficient for accurate parameter estimation

Engineering Contradiction:

Improveefficiency of parameter estimationVSAvoidaccuracy of equivalent circuit model parameters

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system dynamically generates augmented stimulus current that is superimposed on the load current. This dynamic stimulus adaptation ensures that sufficient spectral content is injected at each frequency sub-band corresponding to the battery's time constants, enabling accurate in-situ parameter estimation without requiring offline characterization.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent introduces an intermediary stimulus current as a mediator between the load current and the battery. This augmented current serves as a spectral enrichment tool that provides the necessary frequency content for accurate parameter estimation while maintaining the natural load operating conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If traditional equivalent circuit modeling is used, then battery impedance is modeled with series of parallel-coupled resistors and capacitors, but detailed impedance knowledge requires complex measurement procedures

Engineering Contradiction:

Improveusefulness for fuel-gauging and safety limitsVSAvoidcomplexity of measurement system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the equivalent circuit model into multiple RC pairs, each associated with a specific time constant and frequency sub-band. This segmentation allows independent estimation of each RC pair's parameters through spectral analysis of the battery's voltage and current responses, simplifying the measurement and estimation process while maintaining model accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces complex physical impedance measurement procedures with signal processing-based parameter estimation. By using spectral analysis and signal decomposition techniques, the system extracts detailed impedance characteristics from voltage and current waveforms without requiring dedicated impedance measurement hardware or complex test setups.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12601787B2Estimation of battery equivalent circuit model parameters by decomposition of sense current and terminal voltage into subbands

Publication Date: 2026.04.14 CIRRUS LOGIC INC

AI summary

A method for estimating equivalent circuit model parameters of a battery may include measuring a battery voltage across terminals of the battery and a battery current drawn from the battery, decomposing the battery voltage and the battery current into a plurality of sub-bands, each sub-band of the plurality of sub-bands based on a time constant that characterizes a temporal behavior of the battery, for each sub-band of the plurality of sub-bands, estimating an equivalent resistance for such sub-band based on a spectral content of the battery voltage and battery current for such sub-band, and estimating an open circuit voltage of the battery based at least on the spectral content of the battery voltage and battery current present in one of the plurality of sub-bands and the equivalent resistances of the plurality of sub-bands.