Battery Impedance Estimation via AC and DC Signal Segmentation
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Solution Overview
Problem
Existing battery impedance estimation methods face inaccuracies due to data noise from low resistance measurements, leading to errors in estimating resistance values.
Innovation Solution
A battery characteristic estimation device and method that calculates first and second electrical characteristic values using frequency-dependent and transient response data, respectively, to accurately estimate impedance by employing a device with a controller, current output part, voltage measurement part, and storage, which applies alternating and direct currents to measure output voltages and calculate reaction, serial, and diffusion resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement is performed on battery with low resistance value, then measurement range is extended, but data noise increases and measurement precision deteriorates
Solution Approach 1:
The patent segments the impedance measurement into two distinct components: frequency-dependent impedance (measured using AC signals at multiple frequencies) and transient response impedance (measured using DC step signals). By separating these measurements and processing them differently, the system can accurately estimate low resistance values without being overwhelmed by measurement noise, thus resolving the contradiction between extending measurement range and maintaining precision.
2Reliability
If resistance value estimation is performed using impedance data, then electrical characteristic is obtained, but estimation error increases when resistance is low
Solution Approach 1:
The patent introduces an equivalent circuit model as an intermediary between raw impedance measurements and resistance estimation. The model includes frequency-dependent components (reaction resistance) and transient response components (serial resistance and diffusion resistance). By fitting measurement data to this intermediate model, the system can accurately extract resistance values even when direct measurements are noisy, thus improving reliability without sacrificing precision.
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 approach allows for precise impedance estimation of batteries by combining frequency-dependent and transient response data, improving energy efficiency and reducing estimation errors.
Implementation Method 1
frequency-dependent data that is data of an output voltage of the secondary battery changed by a frequency of alternating current applied to the secondary battery
Implementation Method 2
transient response data that is data of the output voltage of the secondary battery attenuated by a change in direct current applied to the secondary battery
Data Source
AI summary
A battery characteristic estimation device includes a first calculation part configured to calculate a first electrical characteristic value of a secondary battery on the basis of frequency-dependent data that is data of an output voltage of the secondary battery changed by a frequency of alternating current applied to the secondary battery, a second calculation part configured to calculate a second electrical characteristic value of the secondary battery on the basis of transient response data that is data of the output voltage of the secondary battery attenuated by a change in direct current applied to the secondary battery, and an estimation part configured to estimate an electrical characteristic value of the secondary battery on the basis of the first electrical characteristic value and the second electrical characteristic value.