Battery Cell Temperature Estimation via EIS Without Thermistors
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Solution Overview
Problem
Existing battery monitoring systems rely on thermistors attached to battery cell casings, which increase cost and weight with the number of cells, and may not accurately measure core cell temperatures due to thermal lag.
Innovation Solution
The use of Electro-chemical Impedance Spectroscopy (EIS) to estimate battery cell temperature by measuring voltage and current, which includes a frequency component, and relating multiple features of impedance to temperature through a feature vector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermistors are attached to battery cell casings for temperature monitoring, then temperature measurement capability is provided, but cost and weight increase with the number of cells
Solution Approach 1:
The existing voltage and current measurement circuits in the battery management system are made multi-functional by using them to perform both electrical parameter measurement and temperature estimation through EIS techniques, eliminating the need for separate thermistor sensors
Solution Approach 2:
The battery cell itself is used to provide the measurement signal through its inherent electrical properties (impedance), which naturally varies with temperature, eliminating the need for external sensing components
2Measurement precision
If additional wiring and sensors are added for temperature monitoring, then temperature measurement capability is improved, but device complexity increases
Solution Approach 1:
The existing voltage and current measurement circuits are made multi-functional by using them to perform both electrical parameter measurement and temperature estimation through EIS techniques, eliminating the need for separate thermistor sensors and reducing overall system complexity
Solution Approach 2:
The battery cell itself is used to provide the measurement signal through its inherent electrical properties (impedance), which naturally varies with temperature, eliminating the need for external sensing components and reducing device complexity
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
EIS-based temperature estimation achieves accurate core cell temperature measurement with less than 1°C error over a wide frequency and temperature range, without the need for additional wiring or sensors, thereby reducing costs and improving monitoring efficiency.
Implementation Method 1
Electrochemical impedance spectroscopy (EIS) is a technique used to characterize electrochemical systems by measuring the impedance of the system as a function of frequency
Implementation Method 2
The temperature estimation circuit is configured to estimate an impedance based on the frequency component
Implementation Method 3
estimate a temperature based on a feature vector including at least two features of the impedance
Data Source
AI summary
A temperature estimation apparatus includes a measurement circuit and a temperature estimation circuit. The measurement circuit is configured to acquire a voltage measurement and a current measurement. The voltage measurement and the current measurement include a frequency component. The temperature estimation circuit is coupled to the measurement circuit. The temperature estimation circuit is configured to estimate an impedance based on the voltage measurement and the current measurement, and estimate a temperature based on a feature vector including at least two features of the impedance.