Battery Charging Control from Two-Point Impedance Change
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Solution Overview
Problem
When measuring the impedance of a battery during charging, especially at high charging rates, the uneven distribution of lithium in the electrodes affects the measurement results, making it difficult to accurately diagnose battery degradation due to the interference from lithium diffusion processes.
Innovation Solution
A method where a superimposed current with a periodically changing waveform is input to the battery at predetermined frequencies to measure impedance at two time points, with the current value of the charging current adjusted based on the increase state of the second impedance to the first impedance, using parameters like the increase ratio to maintain optimal charging conditions and minimize lithium unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging rate of the charging current is increased to reduce charging time, then productivity is improved, but the measurement precision of impedance is worsened due to lithium uneven distribution affecting the measurement results
Solution Approach 1:
The patent applies preliminary action by measuring the impedance at an initial stage (before significant lithium uneven distribution occurs) and comparing it with impedance measured at later stages. This allows the system to detect changes in impedance characteristics that indicate lithium unevenness before it severely degrades measurement accuracy, enabling corrective actions to be taken proactively.
Solution Approach 2:
The patent implements feedback by continuously monitoring impedance measurements during charging and using these measurements to adjust the charging rate. When impedance changes indicate lithium uneven distribution, the system reduces the charging rate to restore uniform lithium distribution, thereby maintaining measurement precision while still achieving efficient charging overall.
2Measurement precision
If the charging rate is reduced to improve impedance measurement accuracy, then measurement precision is improved, but the charging time increases reducing productivity
Solution Approach 1:
The patent applies periodic action by intermittently reducing the charging rate at specific intervals during the charging process. Instead of maintaining a constantly low charging rate, the system periodically pauses or reduces charging to allow lithium uniformization, then resumes at higher rates. This periodic modulation achieves both measurement accuracy and acceptable charging time.
Solution Approach 2:
The patent implements dynamics by making the charging rate adjustable and adaptive throughout the charging process. The system dynamically transitions between different charging rates based on real-time impedance measurements and detected lithium distribution states, optimizing the balance between charging speed and measurement accuracy at each moment rather than using a fixed rate.
3Productivity
If a high charging rate is used during impedance measurement, then the charging efficiency is improved, but the reliability of battery diagnosis is worsened due to interference from lithium diffusion processes
Solution Approach 1:
The patent applies the taking out principle by separating the impedance measurement process from the high-rate charging process. The system performs impedance measurements at reduced charging rates or at specific intervals when lithium distribution is known to be uniform, extracting pure degradation signals from the composite signals that would otherwise include lithium diffusion effects. This allows accurate battery diagnosis to be obtained without compromising overall charging efficiency.
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
This approach allows for accurate impedance measurement and battery diagnosis by adjusting the charging current to appropriate magnitudes, reducing the impact of lithium unevenness and effectively determining battery degradation states.
Implementation Method 1
the frequency characteristic of the impedance of the battery is measured, and the state of the battery including the degradation state of the battery is diagnosed based on the measurement result of the frequency characteristic of the impedance
Implementation Method 2
a superimposed current obtained by superimposing a periodically changing current waveform (the current waveform of an AC current) on a charging current is input to the battery, thereby measuring the impedance of the battery
Data Source
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AI summary
In a charging method of a battery (6) of an approach, at each of a first time point and a second time point after a time point at which a predetermined time is elapsed from the first time point, a superimposed current (Ia(t)) obtained by superimposing a current waveform that periodically changes at a predetermined frequency (F0) on a charging current is input to the battery (6), thereby measuring, concerning an impedance of the battery (6) at the predetermined frequency (F0), a first impedance at the first time point and a second impedance at the second time point. In the charging method, using a parameter representing an increase state of the second impedance to the first impedance as an index, a current value of the charging current is adjusted.