Battery Cell Diagnostic Apparatus Multi-Frequency Impedance Analysis
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Solution Overview
Problem
Lithium-ion and lithium-polymer batteries face issues with mismatched cells, which can lead to performance diminishment and safety concerns due to varying electrolyte resistance, anode and cathode impedances, state of charge, and temperature differences, causing potential catastrophic failures.
Innovation Solution
A battery cell diagnostic apparatus using multi-frequency impedance measurements to assess electrolyte resistance, anode and cathode impedances, and temperatures, allowing for cell matching and health evaluation before and after assembly, and enabling detection of mismatched cells in both individual and assembled batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-frequency impedance measurements are implemented to measure electrolyte resistance, anode impedance, and cathode impedance, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the battery cell into three distinct measurement components: electrolyte resistance (measured at high frequency where capacitive effects are minimized), anode impedance (measured at intermediate frequency), and cathode impedance (measured at low frequency). This segmentation allows each component to be measured independently at its optimal frequency, achieving precise measurement of all three parameters without requiring three separate diagnostic devices.
Solution Approach 2:
The diagnostic apparatus employs a universal measurement system that can measure multiple battery parameters (electrolyte resistance, anode impedance, cathode impedance, state of charge, state of health, temperature) using a single multi-frequency impedance measurement platform. The system applies AC signals at different frequencies and processes the responses to extract multiple parameters simultaneously, eliminating the need for separate measurement devices for each parameter.
2Reliability
If cell matching is performed based on multiple attributes including temperature and impedance, then reliability is improved, but measurement precision requirements increase
Solution Approach 1:
The patent performs preliminary measurements of all critical attributes (electrolyte resistance, anode impedance, cathode impedance, state of charge, state of health, and temperature) on individual battery cells before they are assembled into a battery pack. This preliminary characterization allows cells to be sorted and matched into groups with consistent attributes, ensuring reliable performance from the outset. The multi-frequency impedance measurements are conducted in advance to establish baseline data for matching.
Solution Approach 2:
The patent utilizes parameter changes in the measurement frequency domain to differentiate between various battery cell attributes. By measuring impedance across multiple frequencies (high, intermediate, and low), the system can distinguish between electrolyte resistance, anode impedance, and cathode impedance based on their frequency-dependent characteristics. This parameter-based differentiation enables precise measurement of multiple attributes using a single measurement platform.
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
The solution effectively identifies and groups matched battery cells, improving performance and safety by ensuring consistent attributes, reducing failure risks, and facilitating forensic analysis of failed batteries.
Implementation Method 1
A battery cell diagnostic apparatus using multi-frequency impedance measurements to assess electrolyte resistance, anode and cathode impedances
Implementation Method 2
control the second multiplexer to electrically connect the current source to the battery cell to apply a current, output from the current source, at each of a set of frequencies to the battery cell
Data Source
AI summary
An example battery cell diagnostic apparatus is provided that may include control circuitry, a current source, measurement circuitry, and a first and a second multiplexer. The control circuitry may be configured to control the first multiplexer to electrically connect the measurement circuitry to a battery cell and control the second multiplexer to electrically connect the current source to the battery cell to apply a current, output from the current source, at each of a set of frequencies to the battery cell. The control circuitry may also be configured to receive measurements from the measurement circuitry at each of the frequencies, which may include respective frequencies that correlate to an electrolytic resistance of the battery cell, an anode impedance of the battery cell, and a cathode impedance of the battery cell. Similar measurements may also be taken for each cell in a battery.