Battery Cell Current Limiting Using Predictive RMS Thermal Control
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Solution Overview
Problem
The risk of overheating in battery cells, particularly in electric vehicles, leads to potential leakage and accelerated aging due to unmonitored components, affecting power loss and service life, necessitating a method to control the maximum permissible current to prevent thermal damage.
Innovation Solution
A battery management system calculates a predictive RMS limiting value for the cell current based on temperature and time intervals using a PT1-element model, adjusting current limits dynamically to prevent overheating through a proportional-integral controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the cell current is increased to improve power output, then the available power increases, but the risk of overheating and thermal damage increases
Solution Approach 1:
The patent implements dynamic current limiting values that adapt in real-time based on temperature measurements and time intervals. The BMS continuously adjusts the maximum permissible cell current according to current thermal conditions, allowing higher currents when temperatures are low and reducing currents when temperatures rise, thus optimizing power output while preventing overheating
Solution Approach 2:
The system employs feedback mechanisms by continuously monitoring cell temperature via temperature sensors and using this information to adjust current limiting values. The BMS measures temperature, compares it against thresholds, and dynamically modifies the permissible current accordingly, creating a closed-loop control system that balances power delivery with thermal safety
2Reliability
If the cell current is limited to prevent overheating, then thermal protection is improved, but the available power decreases
Solution Approach 1:
The current limiting values are not static but dynamically adjusted based on real-time temperature conditions and time intervals. The system allows maximum current when temperatures are within safe ranges and progressively reduces current limits as temperatures approach critical thresholds, ensuring thermal protection while maximizing power availability under safe operating conditions
Solution Approach 2:
The system changes the current limiting parameter dynamically based on temperature and time. By modifying the current limit parameter according to thermal conditions and duration of current flow, the system maintains reliability through thermal protection while optimizing power output when conditions permit
3Reliability
If temperature monitoring is extended to unmonitored components, then thermal protection is improved, but device complexity increases
Solution Approach 1:
The patent introduces a thermal model as an intermediary that estimates temperatures of unmonitored components (such as current collectors and sealing materials) based on measurements from existing temperature sensors. This mathematical model predicts thermal conditions in areas without direct sensor contact, extending thermal protection coverage without requiring physical sensors in every location
Solution Approach 2:
The system creates virtual representations (thermal models) of unmonitored components that replicate their thermal behavior based on monitored parameters. By copying the thermal characteristics of current collectors and sealing materials through mathematical models, the system achieves monitoring coverage for these critical components without physical sensors
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
The method efficiently limits current to ensure thermal protection and full capacity availability of battery cells, allowing intelligent power management and reducing the risk of premature aging.
Implementation Method 1
this effect has a direct influence upon the available power, and can shorten the service life of the battery cell
Data Source
AI summary
A method for controlling a cell current limiting value for a battery management system. In some examples, the method includes determining quadratic reference currents of a battery cell; calculating a corresponding reference time constant for each reference current using a model for the calculation of a RMS value of a cell current by reference to a continuous current; constituting a diagram for the relationship between the reference time constant and the quadratic reference current; determining a predictive time constant by the comparison of a quadratic measured value of a cell current with the quadratic reference currents; calculating a predictive RMS limiting value of the cell current; calculating a first predictive limiting value for a short predictive time, a second predictive limiting value for a long predictive time, and a third predictive limiting value for a continuous predictive time; and calculating additional RMS limiting value for the cell current.