SOC Estimation Using Temperature Coefficient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) of secondary cells, such as lithium-ion cells, require complex calculations involving open circuit voltage measurements, leading to increased arithmetic circuit burden and costs, and struggle to manage constant current charging and discharging effectively.
Innovation Solution
Calculating the value of (∂Eemf/∂T) in advance and using it to estimate SOC based on temperature and current measurements, eliminating the need for open voltage measurements and reducing computational burden, allowing for accurate SOC estimation directly from temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open circuit voltage measurement method is used to estimate state of charge, then measurement precision is improved, but device complexity and measurement time increase due to requiring the cell to remain unused for extended periods
Solution Approach 1:
The patent changes the measurement parameters from open circuit voltage (requiring static conditions) to temperature and current measurements (which can be taken during active charging/discharging). By measuring temperature change rate and current, the system calculates state of charge without requiring the cell to be at rest, thus resolving the time loss issue while maintaining accuracy through alternative physical parameters
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to estimate state of charge. Instead of directly measuring open circuit voltage, the system uses temperature change rate during charging/discharging as a mediator to infer state of charge, allowing continuous monitoring without requiring the cell to be unused
2Measurement precision
If complex calculation methods involving simultaneous differential equations are used, then state of charge estimation accuracy is improved, but arithmetic circuit burden increases
Solution Approach 1:
The patent extracts only the essential parameters needed for state of charge estimation (temperature change rate and current) and removes unnecessary complex calculations. By focusing on the direct relationship between temperature change, current, and state of charge, the system eliminates the need for solving simultaneous differential equations while maintaining sufficient accuracy for practical applications
Solution Approach 2:
The patent segments the state of charge estimation process into discrete, manageable steps: measuring current, measuring temperature change rate, and calculating state of charge using a simplified formula. This segmentation breaks down the complex estimation process into simple, computationally efficient operations that reduce arithmetic circuit burden
3Measurement precision
If open circuit voltage measurement is required, then state of charge estimation accuracy is improved, but ease of operation deteriorates due to requiring the cell to remain unused for several hours
Solution Approach 1:
The patent implements periodic measurement of temperature and current during charging and discharging cycles. Instead of requiring long idle periods for single measurements, the system continuously or periodically measures parameters during active operation, making the estimation process more operationally convenient while maintaining accuracy through multiple data points
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 reduces the computational load on arithmetic circuits, enables efficient management of constant current operations, and minimizes errors in SOC estimation, even with frequent charging and discharging, without requiring the secondary cell to remain unused for extended periods.
Implementation Method 1
calculating a value of (∂Eemf/∂T) in advance on the assumption that Eemf is an electromotive force of the secondary cell and T is a temperature of the secondary cell; and calculating the state of charge based on at least a value of (∂Eemf/∂T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell
Data Source
AI summary
A method of estimating a state of charge of a secondary cell includes: calculating a value of (∂Eemf/∂T) in advance on the assumption that Eemf is an electromotive force of the secondary cell and T is a temperature of the secondary cell; and calculating the state of charge based on at least a value of (∂Eemf/∂T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.