Battery Cell Temperature Detection via Impedance Intercept Frequency
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Solution Overview
Problem
Accurately measuring battery cell temperature, especially in large battery packs, is challenging due to thermal mass and time delays, and existing methods are costly and complex, making it difficult to determine the temperature of each cell within 1K for optimal performance and longevity.
Innovation Solution
The method involves detecting the intercept frequency of the imaginary part of the impedance plot for each battery cell using an intercept detection circuit and a temperature detection circuit, which maps this frequency to determine the cell's temperature, allowing for instantaneous and accurate temperature measurement without complex models or multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are placed inside each battery cell to achieve accurate temperature measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces physical temperature sensors with an electrical impedance-based measurement system. By injecting current at different frequencies and measuring the impedance response, the system determines cell temperature without requiring direct thermal contact sensors inside each cell, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The patent introduces impedance measurement as an intermediary method to indirectly determine temperature. Instead of directly measuring temperature with sensors, the system measures electrical impedance at various frequencies and uses the relationship between impedance characteristics and temperature to infer the cell temperature, avoiding the need for intrusive sensors
2Measurement precision
If thermal models are used to identify individual cell temperatures, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex thermal modeling with direct electrical impedance measurement. By measuring impedance at multiple frequencies and identifying characteristic frequencies related to temperature-dependent processes, the system directly determines cell temperature without requiring complex thermal models, diffusion coefficients, or heat transfer calculations
Solution Approach 2:
The patent changes the measurement parameter from direct thermal measurement to electrical impedance measurement. By measuring impedance at different frequencies and identifying how these electrical parameters change with temperature, the system determines temperature through electrical characteristics rather than thermal models, simplifying the overall approach
3Measurement precision
If multiple temperature sensors are used for each battery cell, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent makes the impedance measurement system multi-functional by using the same current injection and voltage measurement circuitry to determine both cell temperature and cell health status. This single system replaces multiple dedicated sensors, reducing the quantity of components required while providing comprehensive monitoring capabilities
Solution Approach 2:
The patent substitutes electrical impedance measurement for multiple physical temperature sensors. By using electrical measurements to infer temperature, the system eliminates the need for multiple costly temperature sensors per cell, significantly reducing component quantity and overall system cost
4Measurement precision
If temperature measurement is delayed due to thermal mass, then measurement precision is maintained, but productivity decreases
Solution Approach 1:
The patent uses periodic current injection at different frequencies to measure impedance characteristics. By applying alternating current at various frequencies and measuring the resulting voltage response, the system rapidly determines temperature-dependent impedance features without waiting for thermal equilibrium, enabling fast temperature assessment
Solution Approach 2:
The patent replaces slow thermal measurement methods with rapid electrical impedance measurement. Since electrical measurements occur instantaneously compared to thermal processes, the system can determine cell temperature in real-time without being constrained by thermal mass and heat transfer time constants
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 enables precise temperature measurement of battery cell chemistry, reducing measurement errors and time delays, and allows for real-time control of charging and discharging, improving battery pack performance and longevity without the need for complex models or multiple sensors.
Implementation Method 1
detecting an intercept frequency, the intercept frequency being a frequency at which an imaginary part of a plot of impedance values of the battery cell exhibits a zero crossing, with the impedance values corresponding to current injected into the cell
Data Source
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AI summary
Temperature characteristics of battery cells are detected. In accordance with one or more embodiments, an intercept frequency is detected for each battery cell, at which frequency an imaginary part of a plot of impedance values of the battery cell exhibits a zero crossing. The impedance values correspond to current injected into the cell. A temperature of the cell is determined based upon the detected intercept frequency for the cell and stored data that models operation of the cell. Various approaches are implemented with different types of circuits coupled to detect the impedance values of the respective cells.