Battery Cell SOE Estimation Using Internal Resistance and OCV
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for estimating the state of energy (SOE) of a battery cell, particularly in the aeronautical field, are non-deterministic and lack certification, especially in hybrid or fully electric aircraft where batteries are used for propulsion.
Innovation Solution
A method involving measurement of cell temperature, voltage, and current to estimate internal resistance, open circuit voltage, and total energy delivery, using predefined associations to calculate maximum energy and SOE, independent of charge state and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a neural network is used to estimate SOE based on current, voltage and temperature measurements, then the estimation can be performed using available measurements, but the system becomes non-deterministic and difficult to certify in the aeronautical field
Solution Approach 1:
The patent replaces the neural network (statistical/learning system) with a deterministic calculation method based on electrical circuit principles. The SOE is estimated by calculating internal resistance from voltage and current measurements, then using predefined associations with temperature and current to determine total delivered energy and maximum energy, finally computing SOE as the difference. This substitution of a non-deterministic system with a deterministic one enables certification while maintaining estimation functionality.
2Measurement precision
If internal resistance estimation is performed using volt-amperometry measurement, then the estimation accuracy is improved, but the measurement process becomes more complex
Solution Approach 1:
The patent makes the volt-amperometry measurement system multi-functional by using the same voltage and current measurements for multiple purposes: estimating internal resistance, determining operating conditions for energy calculation, and monitoring cell state. This universal use of measurements improves internal resistance estimation accuracy without proportionally increasing system complexity, as the same sensors serve multiple functions.
3Reliability
If the SOE estimation method accounts for internal resistance changes and aging effects, then the accuracy and reliability are improved, but the calculation complexity increases
Solution Approach 1:
The patent performs preliminary action by pre-establishing associations between operating conditions (temperature, current, open circuit voltage) and total delivered energy through prior calibration or experimentation. These predefined associations are stored and readily accessible during operation. This preliminary preparation allows the system to account for internal resistance changes and aging effects during actual use without performing complex real-time calculations, thus improving reliability while keeping operational calculation complexity manageable.
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
Provides a deterministic and certifiable method for estimating battery SOE, accounting for internal resistance changes and aging, ensuring accurate energy estimation for battery management.
Implementation Method 1
adding to the measured voltage a voltage of the internal resistance resulting from a passage of the measured current through the internal resistance
Data Source
AI summary
Estimating the state of energy for a particular time, which includes:receiving measurements of a temperature of the cell, of a voltage of the cell, and of a current exchanged by the cell;estimating an internal resistance of the cell;estimating an open circuit voltage of the cell;estimating a total energy delivered by the cell until the particular time;estimating a maximum energy that can be delivered by the cell, assuming that the temperature and the current remain constant; andsubtracting the estimated total delivered energy from the estimated maximum energy.