Battery EIS Voltage Correction Under Non-Steady DC Conditions

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Solution Overview

Problem

Existing battery monitoring systems face challenges in accurately determining state of charge (SoC) and state of health (SoH) due to inaccurate temperature measurements and interference from alternating current (AC) signals during non-steady state conditions, which can lead to overheating and damage.

Innovation Solution

An electrochemical impedance spectroscopy (EIS) measurement system that adjusts for direct current (DC) voltage changes by using current and voltage measurement devices, along with processing circuitry to determine complex impedance, reducing the impact of AC signals and non-steady state conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If EIS measurement is performed during non-steady state conditions, then measurement speed is improved, but measurement precision deteriorates due to AC signal interference

Engineering Contradiction:

Improvemeasurement speedVSAvoidimpedance measurement accuracy

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent extracts and removes the harmful AC signal components from the measured voltage signal through spectral analysis and filtering. By identifying frequency components that do not match the excitation signal frequency and eliminating them, the system isolates the true impedance response from interference, thereby maintaining measurement precision during non-steady state conditions.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary processing stage involving Fast Fourier Transform (FFT) and inverse FFT operations. This intermediary transformation domain allows separation of the excitation signal response from interfering AC signals by frequency, enabling accurate impedance extraction even when DC voltage is changing, thus resolving the contradiction between speed and precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If DC voltage correction is applied, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

ImproveEIS voltage accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex hardware-based voltage correction circuits with software-based digital signal processing. By using FFT algorithms and mathematical operations in the digital domain to perform DC voltage compensation and AC signal filtering, the system achieves high measurement precision without requiring additional analog components, thereby limiting the increase in device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple EIS measurements with different phases are performed, then measurement precision is improved, but loss of time increases

Engineering Contradiction:

Improveimpedance determination accuracyVSAvoidmeasurement duration

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent utilizes periodic phase shifting of the excitation signal across multiple measurement cycles. By systematically varying the phase and combining results through spectral analysis, the system achieves accurate impedance determination that is independent of transient conditions. The periodic nature allows efficient processing where multiple phase measurements can be combined in the frequency domain rather than requiring sequential time-domain processing.

Inventive Principle:

Principle #19Periodic action

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

Enhances the accuracy of SoC and SoH estimation by minimizing the effects of AC signals and non-steady state conditions, preventing overheating and ensuring reliable battery operation.

Implementation Method 1

An electrochemical impedance spectroscopy (EIS) measurement system to adjust for a change in a direct current (DC) voltage value of an electrochemical cell

Methodology Applied

Scientific EffectElectrochemical impedance spectroscopy:

Data Source

PatentUS20250327871A1Electrochemical impendence spectroscopy including direct current values

Publication Date: 2025.10.23 ANALOG DEVICES INT UNLTD CO

AI summary

An electrochemical impedance spectroscopy (EIS) measurement system to adjust for a change in a direct current (DC) voltage value of an electrochemical cell in an energy storage system can include a current measurement device, which can be arranged for measuring a current through the electrochemical cell. The EIS measurement system can also include a voltage measurement device, which can be arranged to be coupled across the electrochemical cell, for measuring a voltage across the electrochemical cell. The EIS measurement system can also include processing circuitry, which can be coupled to the current measurement device and the voltage measurement device and which can be configured to determine a representation of the DC voltage across the electrochemical cell. The processing circuitry can also be configured to determine an EIS voltage at a specified EIS frequency using the representation of the DC voltage across the electrochemical cell and the measured voltage across the electrochemical cell.