Battery Management System Dynamic Current Limiting
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Solution Overview
Problem
Lithium-ion batteries in electric vehicles face premature ageing due to high root mean square current (IRMS) values, especially at low temperatures or during steep inclines, leading to reduced service life and potential damage, necessitating an increase in limit values without compromising the 15-year warranty.
Innovation Solution
A method to adjust the maximum current delivery based on the frequency distribution of the root mean square current, allowing a higher power output for a portion of the operating time while maintaining the battery's service life by introducing a weighting factor that weakens control as the warranted operating time approaches its end, and controlling the current through setpoint values for different intensity ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the maximum current limit is increased to provide higher power output, then the power delivery capability is improved, but the battery ageing accelerates and service life is reduced
Solution Approach 1:
The patent implements dynamic adjustment of the maximum current limit based on the frequency distribution of root mean square current values. The control parameter is no longer fixed but adapts continuously according to the statistical distribution of actual operating conditions, allowing the system to optimize between power delivery and battery protection in real-time
Solution Approach 2:
The invention changes the control parameter from a fixed current threshold to a statistically derived limit based on the frequency distribution of IRMS values. By analyzing the distribution characteristics and calculating appropriate percentile-based limits, the system dynamically adjusts operational parameters to balance power needs with battery longevity
2Productivity
If the maximum current limit is increased to allow higher power output for short periods, then the productivity is improved, but the temperature gradient and lithium plating effects worsen
Solution Approach 1:
The patent allows temporary exceedance of conservative current limits by utilizing the statistical distribution of operating conditions. By permitting operation at higher currents during periods when the distribution indicates low risk (based on frequency analysis), the system achieves partial excessive action that boosts productivity while maintaining overall safety through statistical control
Solution Approach 2:
The system continuously monitors the frequency distribution of root mean square current values and uses this feedback to dynamically adjust the maximum current limit. This closed-loop approach ensures that higher power outputs are permitted only when historical data indicates such conditions are safe, automatically reducing limits when temperature gradient or lithium plating risks increase
Data Source
AI summary
The invention relates to a method for managing a battery comprising a plurality of battery cells, wherein a maximum value of a current that can be delivered by the battery is adjusted on the basis of a frequency distribution (44) of a root mean square current delivered by the battery. The invention further relates to a battery management system and a computer program for carrying out said method as well as to a motor vehicle comprising a battery which includes a battery management system of said type.