Battery Discharge Voltage Prediction from Two Current Tests
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Solution Overview
Problem
Existing methods for predicting discharge voltage graphs of lithium ion secondary batteries require direct experiments for each discharge current, making it difficult to predict the discharge voltage graph without prior information.
Innovation Solution
A method for predicting discharge voltage graphs using a proportional constant and index parameter to calculate the time required for battery cell voltages to reach discharge limit voltages based on measured times and constant currents, allowing prediction without prior experimental data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct experiments are conducted for each discharge current to obtain discharge voltage graphs, then accurate discharge voltage data is obtained, but extensive experimental testing is required for each current condition
Solution Approach 1:
The patent performs preliminary experiments at only two specific discharge currents (first and second discharge currents) to obtain discharge voltage graphs in advance. These preliminary results are stored and used as basis for predicting discharge voltage graphs at arbitrary discharge currents without conducting additional experiments, thus resolving the contradiction between measurement accuracy and experimental time consumption.
Solution Approach 2:
The patent creates simplified models (first and second discharge voltage graphs) from actual experimental data at two current levels. These models serve as copies that can predict the behavior at arbitrary discharge currents through mathematical relationships, eliminating the need for extensive direct experimentation while maintaining prediction accuracy.
2Loss of time
If discharge voltage graphs are predicted without prior experimental information, then extensive experimental testing is reduced, but prediction accuracy deteriorates
Solution Approach 1:
The patent transforms the prediction problem by changing parameters from predicting entire discharge voltage graphs to predicting specific characteristic values (discharge limit currents at predetermined times, discharge resistances, discharge powers). This parameter transformation enables accurate predictions using simplified models based on only two experimental current levels.
Solution Approach 2:
Instead of attempting to predict the entire discharge voltage graph across all current conditions, the patent focuses on accurately predicting specific local characteristics (discharge limit currents at specific times, discharge resistances at specific times). This localized approach maintains prediction accuracy while significantly reducing experimental requirements.
3Measurement precision
If discharge limit current, discharge resistance, or discharge power is measured at predetermined times through experiments, then accurate battery performance data is obtained, but extensive experimental testing is required
Solution Approach 1:
The patent creates simplified discharge voltage graph models (first and second discharge voltage graphs) from experimental data at two current levels. These models serve as templates that can predict discharge limit currents, discharge resistances, and discharge powers at arbitrary currents through mathematical relationships, eliminating the need for extensive direct measurement experiments.
Solution Approach 2:
The patent develops a universal prediction method where discharge voltage graphs obtained at two specific current levels can predict multiple battery performance parameters (discharge limit currents, discharge resistances, discharge powers) at arbitrary discharge currents. This multi-functional approach increases testing efficiency while maintaining measurement accuracy.
Data Source
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AI summary
A method for predicting a constant current discharge graph for a battery cell according to one feature of the invention includes: measuring a first time required for the battery cell voltage to decrease to a first discharge limit voltage by a first constant current discharge; measuring a second time required for the battery cell voltage to decrease to a second discharge limit voltage by a second constant current discharge; and calculating a proportional constant and an index parameter in the relationship between the constant current and the discharge time during a discharging based on the first constant current and the first time, and the second constant current and the second time. The first discharge limit voltage is a voltage obtained by subtracting the first voltage drop due to the first constant current and the internal resistance of the battery cell from the discharge reference voltage when the discharge current is 0, and the second discharge limit voltage is a voltage obtained by subtracting the second voltage drop due to the second constant current and the internal resistance of the battery cell from the discharge reference voltage.