Battery SOH Estimation via Low Frequency Impedance
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Solution Overview
Problem
Existing methods for determining the State of Health (SOH) of rechargeable batteries are inaccurate, especially when batteries are partially charged, and are not compatible with various computational capabilities, leading to unsafe usage or premature replacement.
Innovation Solution
A method and system that detect the charging state of a battery by adding a low frequency current or voltage signal, calculate internal impedance and Open Circuit Voltage (OCV) values, and use a machine learning model to determine SOH based on these parameters, eliminating the need for complete charge or discharge monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SOC based techniques are used to determine SOH, then the estimation can be performed during battery operation, but the accuracy deteriorates due to errors from initial SOC choice
Solution Approach 1:
The patent introduces an exogenous low frequency current signal as an intermediary to excite the battery system. This external signal serves as a mediator that enables accurate impedance measurement without requiring the battery to be at a specific SOC state, thus resolving the contradiction between operational availability and measurement accuracy
Solution Approach 2:
The patent changes the measurement approach by using frequency domain analysis of impedance parameters instead of relying on SOC-based methods. By measuring impedance at different frequencies and analyzing the frequency response, the system achieves accurate SOH estimation independent of the battery's charging state
2Measurement precision
If monitoring is performed until complete charge or discharge, then accurate SOH estimation can be achieved, but time and resource consumption increases
Solution Approach 1:
The patent applies partial action by injecting a low frequency current signal during normal charging operations rather than requiring complete charge or discharge cycles. This partial excitation signal provides sufficient information for accurate impedance measurement and SOH estimation without the time cost of full charge/discharge monitoring
Solution Approach 2:
The system performs preliminary impedance measurements during regular charging operations using superimposed low frequency signals. This preliminary action during normal operation provides continuous SOH estimation without waiting for complete charge/discharge cycles, saving time while maintaining accuracy
3Ease of manufacture
If related art techniques are used for SOH estimation, then the method may be simple to implement, but the technique fails or provides erroneous results when batteries are partially charged or discharged without resting period
Solution Approach 1:
The patent transitions from static measurement methods (requiring resting periods) to dynamic measurement methods. By continuously injecting low frequency excitation signals during charging operations, the system maintains reliability under dynamic partial charge conditions without requiring the battery to be stationary or at rest
4Adaptability or versatility
If existing SOH determination methods are used, then the system may work with basic computational resources, but the accuracy deteriorates for devices with varying computational capabilities
Solution Approach 1:
The patent creates a universal SOH estimation method that functions across different computational platforms. The frequency domain impedance measurement approach can be implemented with varying computational resources while maintaining accuracy, making the system adaptable from smartphones to EVs and aircraft
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 accurate SOH estimation at partial charge states, compatible with different computational devices, and helps in planning maintenance, preventing internal short circuits and thermal runaway.
Implementation Method 1
calculating an internal impedance and Open Circuit Voltage (OCV) values based on the one or more parameters
Data Source
AI summary
Provided are a method and system for determining State of Health (SOH) of a battery. The method includes: detecting a charging state of the battery that is being charged by a Constant Current (CC) or a Constant Voltage (CV); adding a low frequency current signal to the CC that is charging the battery to obtain a low frequency charging current, or adding a low frequency voltage signal to the CV, that is charging the battery to obtain a low frequency charging voltage; determining one or more parameters relating to the battery during the charging state of the battery; calculating an internal impedance and Open Circuit Voltage (OCV) values based on the one or more parameters; and determining SOH of the battery based on the calculated internal impedance and the OCV values.