Adaptive SOC Calculation for Battery Cells
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Solution Overview
Problem
Existing battery systems for electric vehicles and power supply devices face challenges in precisely calculating the state of charge due to discontinuous changes caused by frequent current fluctuations, leading to inaccurate remaining capacity assessments.
Innovation Solution
A battery system comprising a state-of-charge calculation unit that combines current-based and voltage-based state of charge calculations using weight coefficients adjusted based on the charging, discharging, or stopped state of the battery cell, ensuring precise calculation of the combined state of charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If weights are determined based on current change rate, then the calculation responds quickly to current changes, but the calculated remaining capacity discontinuously changes when current changes frequently
Solution Approach 1:
The patent applies dynamics by making the weight coefficients adaptive rather than static. The first weight coefficient for current-based calculation and the second weight coefficient for voltage-based calculation are dynamically adjusted based on the charging/discharging state of the battery cell. This allows the system to respond appropriately to current changes while maintaining calculation accuracy by selecting the most reliable calculation method for each operational state.
Solution Approach 2:
The patent changes the parameters (weight coefficients) based on operational conditions. By determining the first and second weight coefficients according to whether the battery cell is in charging, discharging, or idle state, the system optimizes the contribution of current-based and voltage-based calculations for each state, preventing discontinuous changes and improving overall accuracy.
2Productivity
If current-based calculation is used, then the calculation is simple and fast, but the accuracy decreases when current changes frequently
Solution Approach 1:
The patent merges two calculation methods by combining current-based calculation and voltage-based calculation with appropriate weight coefficients. This hybrid approach allows the system to leverage the speed advantage of current-based calculation while compensating for its accuracy limitations through voltage-based calculation, achieving both fast and accurate state of charge determination.
Solution Approach 2:
The patent dynamically changes the weight coefficients based on operational state. When the battery cell is in a stable charging or discharging state, the current-based calculation is given higher weight for speed. When the state changes or is unstable, the voltage-based calculation is given higher weight for accuracy, thus adapting the calculation parameters to maintain both speed and precision.
3Measurement precision
If voltage-based calculation is used, then the accuracy is maintained, but the calculation becomes more complex
Solution Approach 1:
The patent applies dynamics by selectively applying different calculation methods based on operational state rather than using a single complex method continuously. The system dynamically determines which calculation approach (current-based, voltage-based, or combined) is most appropriate for the current charging/discharging state, reducing unnecessary computational complexity while maintaining accuracy.
Solution Approach 2:
The patent segments the calculation process into different modes based on operational state. By dividing the state of charge calculation into current-based segment, voltage-based segment, and combined segment, each activated according to specific conditions, the system manages complexity by only executing the necessary calculation method for each state rather than always using the most accurate but complex combined approach.
Data Source
AI summary
Provided is a battery system capable of accurately calculating a state of charge of a battery cell, an electric vehicle, a movable structure, an electricity storage device, and a power supply device. A current-based SOC calculation unit calculates a current-based SOCi on the basis of current flowing in a battery cell. A voltage-based SOC calculation unit calculates a voltage-based SOCv on the basis of the terminal voltage of the battery cell. A combined SOC calculation unit calculates a combined SOCt by weighting the SOCi and the SOCv with the respective weight coefficients (1−α) and α, and combining the weighted SOCi and SOCv. The weight coefficients (1−α) and α are determined based on whether the battery cell is in a charging state, a discharging state, or a charge/discharge stopped state.