Secondary Battery Degradation Measurement via Impedance Calculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring the degradation of secondary batteries, such as lithium-ion batteries, are inaccurate due to difficulties in stopping discharge for open voltage measurement, leading to incorrect calculation of recovered capacity and degradation.
Innovation Solution
A degradation measurement device and method that includes a battery sensing section, current sensing section, and control section to measure voltage and current, calculate internal impedance, and determine open voltage while continuing discharge, allowing for accurate calculation of recovered capacity and degradation without fully discharging the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discharge is stopped to measure open voltage, then measurement accuracy is improved, but productivity deteriorates due to inability to measure during continuous discharge operation
Solution Approach 1:
The control section预先 stores the external impedance value in advance, and during continuous discharge, calculates the open voltage by combining this pre-stored external impedance with the internally calculated impedance and measured discharge current, eliminating the need to stop discharge for measurement
Solution Approach 2:
The patent introduces impedance calculation as an intermediary method to obtain open voltage indirectly during discharge. By measuring terminal voltage and discharge current, calculating internal impedance, and combining with pre-stored external impedance, the system derives open voltage without interrupting discharge operation
2Measurement precision
If open voltage is measured after several hours of discharge stop, then convergence accuracy is improved, but loss of time increases due to extended measurement period
Solution Approach 1:
The patent enables continuous discharge operation throughout the measurement process. The control section continuously monitors discharge current, calculates internal impedance in real-time, and computes open voltage without interrupting the discharge flow, maintaining continuous useful action throughout measurement
Solution Approach 2:
The patent replaces the time-based physical waiting method (stopping discharge for several hours to allow voltage convergence) with a calculation-based approach. By using impedance calculations and pre-stored external impedance values, the system substitutes the mechanical/waiting process with computational methods to achieve the same measurement goal instantly
3Measurement precision
If discharge capacity reference value is set high, then measurement accuracy is improved, but productivity deteriorates due to extended discharge time required
Solution Approach 1:
The control section continuously monitors the integrated discharge capacity during discharge and provides feedback to determine when the predetermined discharge capacity reference value is reached. This feedback mechanism allows the system to dynamically control the measurement process, ensuring accurate recovered capacity calculation while optimizing discharge time based on real-time capacity accumulation
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 precise and efficient measurement of secondary battery degradation during continuous discharge, reducing the time required for maintenance and improving the accuracy of capacity assessment.
Implementation Method 1
a battery sensing section that measures a voltage across a secondary battery
Implementation Method 2
a current sensing section that measures a current flowing through the secondary battery
Implementation Method 3
calculates an internal impedance present in the secondary battery at the second measurement time based on the voltage measured by the battery sensing section
Data Source
AI summary
A battery sensing section measures a voltage across a secondary battery. A current sensing section measures a current flowing through the secondary battery. A control section holds the value of an external impedance present in a discharge path outside the secondary battery, discharges the secondary battery from a first time to a second time at which an integrated discharge capacity based on a measured discharge current becomes equal to a predetermined discharge capacity reference value, calculates the internal impedance present in the secondary battery at the second time based on the measured voltage, calculates the second open voltage at the second time by multiplying the sum of the external impedance and the internal impedance by the measured discharge current, and calculates the recovered capacity of the secondary battery based on the first open voltage at the first time, the second open voltage and the discharge capacity reference value.