Battery Cell Unit Impedance Spectroscopy Monitoring
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Solution Overview
Problem
Existing battery management systems in hybrid and electric vehicles face challenges in ensuring the safety and reliability of lithium-ion battery cells due to complexities in overcharge protection, overcurrent protection, and the potential for malfunctions that can lead to thermal runaway, which complicates the integration of safety devices in series circuits and increases the risk of battery system failures.
Innovation Solution
A battery cell unit with integrated monitoring electronics that employs impedance spectroscopy to determine the complex impedance of the battery cell, allowing for precise state monitoring and prediction, thereby enhancing safety by identifying critical states and enabling proactive measures to prevent thermal runaway through intrinsic electrical safety mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional battery management systems use simple voltage and current monitoring, then the device complexity is low, but the measurement precision and reliability of battery state assessment are insufficient
Solution Approach 1:
The patent replaces simple voltage and current monitoring with impedance spectroscopy measurement. By applying alternating currents at different frequencies and measuring the resulting voltages, the system obtains complex impedance data that provides detailed information about battery internal state, including state of charge, state of health, and detection of internal short circuits, thereby significantly improving measurement precision without requiring complex additional hardware
Solution Approach 2:
The monitoring device utilizes the battery cell's own electrical characteristics by applying measurement currents directly to the battery and measuring its response. This self-service approach allows the battery to provide its own diagnostic information through impedance spectroscopy, eliminating the need for separate complex testing equipment while achieving high-precision state assessment
2Power
If battery cells are connected in series to achieve high voltage, then the power and energy capacity increase, but the reliability decreases due to increased risk of thermal runaway and difficulty in integrating safety devices
Solution Approach 1:
The patent implements preliminary detection of critical battery states through impedance spectroscopy measurements taken during normal operation. By continuously monitoring complex impedance and detecting changes that indicate internal short circuits or thermal runaway precursors, the system can take preventive actions before failures occur, thereby maintaining high reliability in high-voltage series configurations
Solution Approach 2:
The monitoring device provides continuous feedback on battery cell states through impedance spectroscopy measurements. This feedback mechanism enables real-time detection of deviations from normal operation, allowing the control system to adjust charging/discharging parameters or isolate problematic cells, thus maintaining system reliability even when multiple cells are connected in series for high power output
3Loss of information
If simple monitoring methods are used, then the ease of operation is high, but the loss of information about critical battery states occurs
Solution Approach 1:
The patent employs periodic impedance spectroscopy measurements at different frequencies to comprehensively assess battery state. By systematically applying alternating currents at multiple frequencies and analyzing the frequency-dependent impedance response, the system obtains complete information about battery internal conditions, including detection of internal short circuits and assessment of state of charge and health, without requiring complex continuous monitoring
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 use of impedance spectroscopy provides detailed information on the state of the battery cell, enabling more precise state of charge, health, and functionality assessments, significantly increasing the safety and reliability of the battery cells and systems by allowing for early detection and mitigation of critical conditions.
Implementation Method 1
In an impedance spectroscopy mode, measurement currents are applied to the battery cell in order to perform impedance spectroscopy of the battery cell, the measurement currents comprising alternating currents at different frequencies
Data Source
AI summary
A battery cell unit includes a battery cell and a monitoring device for monitoring the state of the battery cell. The monitoring device comprises an actuating device configured to activate an impedance spectroscopy mode provided by the battery cell unit, in which impedance spectroscopy mode measurement currents can be applied to the battery cell to perform impedance spectroscopy of the battery cell, said measurement currents flowing through the battery cell and comprising alternating currents at different frequencies. The monitoring device also comprises a sensor device designed to detect the measurement currents and the corresponding measurement voltages, each of which is a battery cell voltage arising as a response to a measurement current, such that a complex impedance of the battery cell can be determined from the measured values of the measurement currents and the measurement voltages as a function of the frequency of the measurement currents within predetermined tolerance limits.