Battery Reactive Impedance Measurement Using Time Offset Alignment
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Solution Overview
Problem
Conventional methods for determining battery reactive impedance require high-frequency sampling and precise timing control, are costly, and need unique excitation current knowledge, making them inefficient and expensive for complex battery systems like electric vehicles.
Innovation Solution
A time-domain based impedance measurement system that determines a time offset to align voltage and current waveforms, allowing for cost-effective and efficient impedance calculation without high-frequency sampling or precise phase knowledge, compatible with existing systems and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high-frequency sampling methods are used for impedance measurement, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the measurement parameter from time-domain high-frequency sampling to frequency-domain analysis at the fundamental excitation frequency. By measuring voltage and current at the specific excitation frequency rather than sampling across a broad frequency range, the system achieves accurate impedance measurement without requiring complex high-speed sampling hardware
Solution Approach 2:
The patent replaces the mechanical/electrical high-frequency sampling system with a frequency-domain analysis approach. Instead of using complex hardware to capture and process high-frequency signals, the system uses signal processing techniques to analyze voltage and current measurements at the fundamental excitation frequency, thereby reducing hardware complexity
2Measurement precision
If precise timing control is implemented for voltage and current measurement, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary approach by using the known excitation frequency as a reference. Rather than directly measuring and comparing timestamps of voltage and current waveforms, the system uses the excitation frequency to derive phase information, acting as an intermediary that simplifies the measurement process
Solution Approach 2:
The patent makes the measurement system universal by using the excitation frequency itself as the reference for phase measurement. This frequency serves multiple functions: it drives the battery, provides the reference for synchronization, and enables phase calculation without requiring separate timing control mechanisms
3Measurement precision
If unique excitation current knowledge is required for impedance measurement, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent implements self-service by having the measurement system use the excitation signal already present in the battery system. The same current that drives the battery serves as the excitation signal for impedance measurement, eliminating the need for separate excitation current generation and knowledge
Data Source
AI summary
Systems and methods for battery reactive impedance measurement is generally described. The method can include measuring a voltage of a battery cell. The method can further include measuring a current flowing through the battery cell. The method can further include determining a time offset based on the voltage and the current. The time offset can cause the voltage and current to be in-phase. The method can further include sampling the voltage and the current based on the time offset. The method can further include determining an impedance of the battery cell based on the sampled voltage and sampled shifted current.