Battery Capacity Determination via Impedance Phase Shift
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Solution Overview
Problem
Current methods for determining the capacity of electrical energy stores, such as lithium-ion batteries, require full charging and discharging or precise matching with battery management systems, which are time-consuming and inefficient.
Innovation Solution
A device and method that utilize impedance measurements to determine capacity by analyzing the phase shift between current and voltage, allowing for quick and accurate capacity assessment with minimal and short-term loading, using periodic loads with frequencies between 1 and 15 hertz, and considering additional parameters like temperature and state of charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full charging and discharging is performed to determine capacity, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies partial action by performing only a short-term load test (e.g., 1-15 seconds) instead of complete charge-discharge cycles. The impedance measurement device applies a brief periodic load signal to measure phase shift, which correlates with capacity, without requiring full cycling of the battery. This partial measurement achieves sufficient precision for practical purposes while dramatically reducing time consumption.
Solution Approach 2:
The patent uses preliminary action by pre-establishing the relationship between phase shift characteristics and capacity through prior calibration or modeling. Once the correlation between impedance phase and capacity is established, subsequent capacity determinations can be made rapidly by measuring only the phase shift under brief loading conditions, without repeating full charge-discharge cycles.
2Loss of time
If battery management system data is used for capacity assessment, then loss of time is reduced, but measurement precision deteriorates due to calibration requirements
Solution Approach 1:
The patent enables the battery management system to perform self-diagnosis by directly measuring impedance characteristics of the battery cells. The BMS uses its own existing sensors and control capabilities to measure phase shift during brief load applications, eliminating the need for external calibration equipment or manual testing while maintaining measurement accuracy through direct physical measurement rather than relying on pre-stored calibration data.
3Productivity
If impedance measurement with periodic load is applied, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent achieves universality by designing an impedance measurement device that can perform multiple functions using the same hardware platform. The system can measure not only capacity through phase shift analysis but also monitor battery health, detect cell degradation, and provide diagnostic information. This multi-functionality justifies the added complexity by delivering comprehensive battery assessment capabilities from a single integrated system.
Solution Approach 2:
The patent uses phase shift measurement as an intermediary parameter to indirectly determine capacity. Instead of directly measuring capacity through time-consuming charge-discharge cycles, the system measures the phase difference between voltage and current during brief impedance testing, which serves as a mediator that correlates with capacity. This intermediary measurement approach enables rapid assessment without requiring direct capacity measurement procedures.
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
Enables rapid and reliable determination of electrical energy store capacity, reducing the need for full charging and discharging, and allowing for flexible adaptation to different conditions.
Implementation Method 1
an impedance measurement of the electrical energy storage device to determine the phase shift between current and voltage
Implementation Method 2
determination of the phase shift between the periodic load signal and the measured system response of the electrical energy storage device
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to the determination of the capacitance of an electrical energy storage device, such as for example a rechargeable battery, on the basis of the phase of the complex impedance of the electrical energy storage device. For this, the impedance of the electrical energy storage device is determined by loading the energy storage device with a predefined periodic load and determining the system response which occurs thereto. On the basis of the relationship between the phase of the complex impedance of the electrical energy storage device and the capacitance of the electrical energy storage device it is subsequent possible to determine the capacitance of the electrical energy storage device in a simple and reliable way.