Battery Cell Impedance Monitoring for Fast-Charge Damage Prevention
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Solution Overview
Problem
Existing fast-charging methods for electric vehicle batteries risk damaging the cells due to exceeding their operational limits, and complex, computing-intensive control methods are required to prevent this, which are impractical for user implementation.
Innovation Solution
A method that determines complex AC impedance and temperature characteristics of the battery cells during charging and quiescent phases to adjust charging and discharging profiles, using lookup tables and impedance measurements to detect deviations from normal operation, thereby preventing damage by reducing currents when thresholds are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast-charging methods operate battery cells at the limits of their specification to achieve efficient charging, then charging speed and productivity are improved, but cell damage risk increases due to exceeding operational limits
Solution Approach 1:
The patent performs preliminary determination of complex AC impedance and temperature characteristics before charging to establish safe operating parameters. By pre-characterizing the battery cell's electrical properties and thermal behavior, the system can set appropriate charging current limits that prevent damage while maximizing charging speed, thus resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent implements continuous monitoring of impedance and temperature characteristics during charging operations. By measuring these parameters in real-time and comparing them against predetermined thresholds, the system provides feedback control that adjusts charging current to prevent cell damage while maintaining efficient charging rates, thereby resolving the contradiction between charging speed and cell safety.
2Reliability
If complex, computing-intensive control methods are used to prevent cell damage, then reliability is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent employs relatively simple measurement circuits and lookup tables instead of complex computational models. By using predetermined impedance and temperature characteristic data stored in lookup tables, the system achieves reliable cell protection through simple comparisons rather than intensive real-time calculations, thus reducing device complexity while maintaining high reliability.
Solution Approach 2:
The patent transforms the complex problem of real-time battery state estimation into simpler parameter comparisons by determining characteristic values (impedance and temperature) that capture the essential battery state. By monitoring changes in these specific parameters against predetermined thresholds, the system achieves effective cell protection without requiring complex control algorithms or high computational power.
3Productivity
If impedance measurements are performed during charging mode to determine temperature characteristics, then charging efficiency is maintained, but measurement accuracy may be affected by charging current interference
Solution Approach 1:
The patent performs impedance measurements periodically during charging operations at predetermined intervals or at specific charging stages. By conducting measurements at these periodic intervals rather than continuously, the system maintains charging efficiency while obtaining sufficient data points to accurately determine temperature characteristics and detect cell state changes, thus resolving the contradiction between productivity and measurement precision.
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 safe and efficient charging and discharging of electric vehicle batteries without complex computing, adapting to different aging paths and preventing one-off and subsequent damage, while maintaining battery capacity.
Implementation Method 1
a first impedance characteristic value and a second impedance characteristic value are determined during the charging mode. The first impedance characteristic value and the second impedance characteristic value are each representative of a complex AC impedance of the cell
Data Source
AI summary
A method for charging a cell of an electric energy store includes setting the cell into a charging mode; determining a first and a second impedance characteristic, each representative of a complex alternating current impedance of the cell; determining a first and a second temperature characteristic on the basis of the impedance characteristics, each representative of a temperature of the cell; determining a deviation in the temperature characteristics; and reducing a charging current of the cell in the event that the deviation exceeds a specified temperature threshold value.