Battery Entropy Measurement Using In-Situ Voltage Relaxation
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Solution Overview
Problem
Current methods for measuring thermodynamic data of batteries, such as entropy and enthalpy, are time-consuming, labor-intensive, and cannot be performed in situ or in real-time, limiting their applicability for online diagnostics and health monitoring of batteries in applications like electric vehicles.
Innovation Solution
A method and device for measuring entropy variation of batteries in situ and in real-time, involving preliminary modeling of the battery's electrical and thermal behavior, using recursive least squares algorithms to estimate electrical and thermal parameters, including entropy and enthalpy, allowing for continuous monitoring of battery health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard electrochemical thermodynamic measurement methods are used, then measurement precision of thermodynamic data is improved, but measurement time increases significantly (several days to weeks)
Solution Approach 1:
The patent changes the measurement parameters by using voltage relaxation curves obtained during normal charge-discharge cycles instead of requiring separate equilibrium measurements at multiple temperatures. This transforms the measurement approach from temperature-varied equilibrium measurements to time-based relaxation analysis during operational cycles, dramatically reducing measurement time while maintaining diagnostic value
Solution Approach 2:
The patent performs preliminary modeling of voltage relaxation behavior during normal battery operation to extract thermodynamic parameters. By analyzing voltage relaxation curves that occur naturally during charge-discharge cycles, the system obtains entropy and enthalpy data without requiring separate dedicated measurement campaigns, thus saving time while preserving measurement accuracy
2Measurement precision
If standard laboratory measurement methods are used, then measurement precision is improved, but ease of operation deteriorates (cannot be performed in situ or online)
Solution Approach 1:
The patent makes the battery management system perform multiple functions: it simultaneously manages charge-discharge operations and conducts thermodynamic measurements. The voltage relaxation analysis is integrated into the normal BMS operation, allowing the same system to both control battery charging/discharging and extract thermodynamic parameters like entropy and enthalpy, thus enabling in situ measurement without separate laboratory equipment
Solution Approach 2:
The battery system measures its own thermodynamic parameters by analyzing its own voltage relaxation behavior during normal operation. The BMS uses the battery's inherent voltage response to relaxation as the measurement signal, eliminating the need for external laboratory measurement systems. The system serves itself by using operational data for both control and diagnostic purposes
3Reliability
If comprehensive battery diagnostics are implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent integrates thermodynamic measurement functionality into the existing battery management system without adding separate dedicated measurement hardware. The BMS uses its existing voltage and temperature sensors along with its control capabilities to perform entropy and enthalpy measurements through voltage relaxation analysis, thereby improving reliability through comprehensive diagnostics while avoiding increased device complexity
Solution Approach 2:
The patent merges the thermodynamic measurement function with the battery management system's existing charge-discharge control functions. By combining these functions, the system achieves comprehensive battery diagnostics including entropy, enthalpy, and state of charge monitoring without requiring separate complex measurement systems, thus improving reliability while maintaining manageable 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
Enables rapid, online, and economical estimation of battery parameters like open circuit voltage, internal resistance, and heat capacity, facilitating real-time health monitoring and state of charge determination, thereby improving battery management and safety.
Implementation Method 1
we cut the current and we wait several hours for the voltage at the battery terminals to relax and tend towards OCV
Implementation Method 2
Then, we vary the temperature of the battery, which has the effect of varying the voltage. There is a linear relationship between T beats and OCV
Data Source
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AI summary
The invention relates to a method and a device for measuring, in real time and in situ, thermodynamic data of a battery (enthalpy and entropy). The object of the invention is to provide a reliable method for measuring, in situ, online and in real time, the variation in entropy (ΔS) of a battery. To this end, the method is characterized in that it consists primarily in: (phase I) producing a prior model of the battery: (a) charging the battery; (b) and/or discharging the battery; (c) measuring actual variables; (d) modeling the electrical behavior of the battery during charging (a) and/or discharging (b) in order to estimate the electrical parameters of the battery; (e) estimating electrical parameters of the battery; (f) modeling the thermal behavior of the battery during charging (a) and/or discharging (b) in order to estimate ΔS in situ, online and in real time; (g) estimating ΔS, by using at least one of the electrical parameters estimated in step (d); (phase II) measuring ΔS of the battery during use in any application and with any state of charge by carrying out step (d) and step (f) of phase I, step (e) and step (g); (phase III) optionally storing the data measured/calculated in phase II and/or in phase I. The invention also relates to a method for determining the state of charge and the state of health of a battery on the basis of these thermodynamic data. Another subject of the invention is a device for implementing this method.