Open Circuit Voltage Estimation Without Rest Time
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Solution Overview
Problem
Existing battery management systems struggle to accurately estimate open circuit voltage in real-time, especially in applications where batteries do not have rest times, such as energy storage systems for power generation equipment, due to the influence of internal resistance and continuous charging/discharging operations.
Innovation Solution
An open circuit voltage estimating apparatus that measures and integrates charge/discharge current to calculate a critical time where the integrated current value is zero or changes sign, allowing for the estimation of open circuit voltage by averaging the cell voltage measured during this time, effectively accounting for internal resistance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery cell is stopped to measure exact open circuit voltage, then measurement precision is improved, but productivity deteriorates due to loss of time and interruption of charging/discharging operations
Solution Approach 1:
The system performs preliminary integration of current values during charging/discharging operations to predict when the integrated current will reach zero. This allows the system to proactively identify the optimal measurement timing without interrupting operations, thereby maintaining productivity while ensuring measurement precision when the battery is naturally at equilibrium.
Solution Approach 2:
The system continuously monitors and integrates current values, using this feedback to dynamically determine when the battery has reached a state suitable for open circuit voltage measurement. This feedback mechanism enables real-time adjustment of measurement timing, allowing continuous operations while capturing accurate voltage data when conditions are appropriate.
2Productivity
If open circuit voltage is measured during continuous charging/discharging without rest time, then productivity is maintained, but measurement precision deteriorates due to internal resistance and polarization effects
Solution Approach 1:
The system calculates the critical time point in advance by integrating current values until they reach zero or change sign. This preliminary calculation identifies the exact moment when polarization effects are minimized, allowing the system to schedule measurements at these optimal points without interrupting continuous operations, thus maintaining both productivity and measurement precision.
Solution Approach 2:
The system dynamically adjusts measurement timing based on real-time current integration results. Instead of using fixed time intervals, the measurement schedule is continuously adapted to match the actual operational state of the battery, ensuring measurements are taken at dynamically determined optimal moments when internal resistance effects are minimized.
3Measurement precision
If average voltage over extended period is used to estimate open circuit voltage, then measurement precision improves, but loss of time increases due to longer integration periods
Solution Approach 1:
The system uses preliminary current integration to predict the optimal measurement window, allowing it to concentrate voltage sampling during the most informative time period. This approach achieves accurate estimation using a focused, shorter integration period rather than extending the measurement over a long duration, thereby reducing time loss while maintaining precision.
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 real-time estimation of open circuit voltage during continuous charging/discharging, facilitating accurate state of charge and health monitoring, and preventing voltage deviations between battery cells, thus enhancing safety and performance in battery applications.
Implementation Method 1
the secondary battery is used in a state where a plurality of the secondary batteries are connected in series and/or in parallel so as to be used in a high voltage and/or mass energy storage apparatus
Implementation Method 2
The reason why the open circuit voltage of the battery cell is different from the actual voltage measured from the battery cell is known to be because of internal resistance (ohmic polarization) of the cell and the polarization phenomenon
Data Source
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AI summary
The present disclosure relates to an open circuit voltage estimating apparatus capable of estimating an open circuit voltage even when a battery cell does not have a rest time. The open circuit voltage estimating apparatus according to an embodiment of the present disclosure includes a current measuring unit configured to measure a charge/discharge current of a battery cell; a current integrating unit configured to integrate the current measured by the current measuring unit starting from an initial time; a time calculating unit configured to calculate a critical time, that is a time in which the integrated current value integrated by the current integrating unit is within a critical range; a cell voltage measuring unit configured to measure a voltage of the battery cell; and an open circuit voltage estimating unit configured to estimate an open circuit voltage of the battery cell by calculating an average value of the voltage measured by the cell voltage measuring unit during an operation time starting from the initial time to the critical time.