Battery Impedance Phase Tracking for Non-Rechargeable SOC
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Solution Overview
Problem
Existing methods for determining the state of charge (SOC) of non-rechargeable lithium thionyl chloride batteries are not accurate and efficient, as they are influenced by temperature history and operational conditions, leading to power consumption and complexity in monitoring.
Innovation Solution
Applying a single frequency current perturbation to the battery terminals to measure the complex impedance, specifically the phase of the response signal, which correlates directly with the SOC, allowing for accurate determination without needing to monitor temperature history.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage or current measurements are used to determine battery state of charge, then the measurement process is simple, but the accuracy deteriorates due to temperature sensitivity and discharge rate variations
Solution Approach 1:
The patent replaces simple voltage/current measurements with impedance spectroscopy measurements. By applying an AC signal and measuring the battery's impedance response across multiple frequencies, the system obtains accurate state of charge information that is not affected by temperature or discharge rate, substituting a more sophisticated measurement approach for the inadequate simple electrical measurements.
Solution Approach 2:
The patent introduces impedance spectroscopy as an intermediary measurement method. Instead of directly measuring voltage or current which are sensitive to operating conditions, the system measures impedance characteristics that serve as a more reliable intermediary indicator of state of charge, which can then be correlated to actual charge levels through calibration.
2Measurement precision
If impedance spectroscopy is used to measure battery state of charge, then measurement accuracy improves, but measurement time increases due to multiple frequency measurements
Solution Approach 1:
The patent applies partial impedance spectroscopy by measuring impedance at a limited set of strategic frequencies rather than performing a complete sweep across all frequencies. This partial measurement approach captures sufficient information to determine state of charge accurately while significantly reducing the measurement time required for a full spectral analysis.
Solution Approach 2:
The system performs preliminary calibration during manufacturing or initial use to establish the relationship between impedance characteristics and state of charge for each battery. This preliminary action creates lookup tables or calibration curves that enable rapid state of charge determination during operation without requiring time-consuming real-time spectral analysis.
3Measurement precision
If multiple frequency measurements are performed for impedance spectroscopy, then state of charge determination accuracy improves, but power consumption increases
Solution Approach 1:
The patent performs impedance measurements at only a few selected frequencies rather than conducting exhaustive multi-frequency spectroscopy. This partial measurement strategy obtains sufficient accuracy for state of charge determination while minimizing the power consumption associated with driving the battery at multiple frequency points.
Solution Approach 2:
The patent uses a single impedance measurement setup that can determine multiple battery parameters including state of charge, internal resistance, and health status. This multi-functional approach eliminates the need for separate measurement systems for different parameters, reducing overall power consumption while maintaining measurement accuracy.
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
Provides a simple, robust method to determine SOC independently of temperature history, reducing power consumption and complexity, while maintaining high accuracy.
Implementation Method 1
A rechargeable battery stores energy by the movement of lithium ions from one electrode material to another. During charging, the electrode materials absorb lithium ions.
Implementation Method 2
During discharging, the process reverses and the electrode materials release the lithium ions.
Implementation Method 3
The battery measures its own impedance at multiple frequencies and uses the measured impedance to determine its state of charge.
Data Source
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AI summary
Sensors and methods for determining the state of charge of a battery are described. The state of charge is determined in some instances by applying a current perturbation having a frequency to the battery terminals, monitoring the response signal, and determining the phase of the response signal. The phase may be correlated to the state of charge of the battery, so that once the phase is determined, a determination of the state of charge of the battery may be made. In some situations, the state of charge may be used to determine the operating condition of a load connected to the battery. In some embodiments, the state of charge may be used to determine whether the battery is defective.