Battery Capacity Estimation via AC Impedance Feature Frequency
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Solution Overview
Problem
Existing methods for determining the capacity maintenance ratio of chargeable and dischargeable batteries are inaccurate and require extensive charging and discharging, making them unsuitable for quick assessments, especially in applications like electric vehicles where complete discharge is not feasible.
Innovation Solution
A device that calculates the capacity maintenance ratio based on the frequency characteristics of AC impedance using an alternating signal and temperature data, without the need for complete charging or discharging, by determining feature information from the impedance response and referencing stored relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery is completely discharged and charged to calculate full charge capacity, then the full charge capacity can be accurately obtained, but a sufficient period of time is required and complete discharge is not feasible for backup power supply and electric vehicle batteries
Solution Approach 1:
The patent replaces the mechanical charging/discharging process with an electrical impedance measurement system. By applying an alternating current signal and measuring the voltage response, the system calculates battery capacity through impedance characteristics rather than through physical charge/discharge cycles, achieving rapid assessment without time-consuming battery cycling
Solution Approach 2:
The patent introduces impedance calculation as an intermediary measurement method. Instead of directly measuring charge/discharge capacity, the system uses impedance characteristics (real part and imaginary part) as intermediate parameters to infer full charge capacity, enabling indirect but accurate capacity assessment without complete battery cycling
2Ease of manufacture
If the integrated capacity is divided by the amount of change in battery voltage to calculate full charge capacity, then the calculation is simple, but the full charge capacity cannot be accurately obtained because the integrated capacity is not exactly proportional to the amount of change in battery voltage
Solution Approach 1:
The patent changes the measurement parameters from simple voltage change to impedance characteristics (real part and imaginary part). By measuring the real part of impedance at open circuit voltage and the imaginary part at a specific frequency, the system obtains more accurate parameters that properly reflect battery capacity without relying on the inaccurate proportionality assumption between integrated capacity and voltage change
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 accurate and rapid determination of the capacity maintenance ratio, improving accuracy and allowing for timely assessments without the need for extensive battery cycling.
Implementation Method 1
calculate frequency characteristics of AC impedance of a battery based on a response signal output from the battery in response to an alternating signal
Data Source
AI summary
A capacity maintenance ratio determination device includes an impedance measurement unit and a capacity estimation unit. An alternating signal is applied from a signal generator to a battery. Frequency characteristics of AC impedance are calculated by the impedance measurement unit based on a response signal output from the battery in response to the alternating signal. A feature frequency is determined from the calculated frequency characteristics. The capacity estimation unit includes a memory and a determination unit. A correspondence relationship among a temperature of the battery, the feature frequency and a capacity maintenance ratio is stored in the memory. The determination unit determines the capacity maintenance ratio of the battery based on the temperature of the battery detected by a temperature detector, the determined feature frequency and the correspondence relationship stored in the memory.