Battery Management System Capacity Estimation via Internal Resistance
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Solution Overview
Problem
Existing battery management systems (BMS) fail to accurately estimate battery capacities due to the changing nature of battery characteristics over time, such as internal resistance, which affects the accuracy of capacity calculations, especially during degradation and partial charge/discharge conditions.
Innovation Solution
A battery management system that includes a sensing unit and a main controller unit (MCU) to calculate used, uncharged, maximum, unusable, and total usable capacities by integrating current values and considering open circuit voltage, internal resistance, and temperature, allowing for precise capacity estimation under varying discharge conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed correlations such as open circuit voltage versus state of charge are used to estimate battery capacities, then the estimation process is simple, but the accuracy deteriorates due to changing battery characteristics during degradation and charge/discharge cycles
Solution Approach 1:
The patent applies dynamics by transitioning from fixed static correlations to dynamic adaptive correlations that evolve with battery degradation. The system continuously updates the open circuit voltage versus state of charge relationship based on observed battery behavior, allowing the estimation model to adapt to changing battery characteristics while maintaining operational simplicity
Solution Approach 2:
The patent changes the parameter relationships by introducing degradation-dependent corrections to the voltage-capacity correlation. Instead of using a single fixed correlation, the system modifies the correlation parameters based on detected degradation indicators, thereby maintaining accuracy as battery characteristics change over time
2Measurement precision
If battery internal resistance and other characteristics are monitored to improve capacity estimation accuracy, then measurement precision improves, but device complexity increases due to additional sensors and calculation requirements
Solution Approach 1:
The patent applies universality by designing the battery management system to perform multiple functions using the same sensor infrastructure. The voltage and current sensors used for basic state of charge estimation are also utilized for degradation detection and capacity correction, eliminating the need for separate dedicated sensors and reducing overall system complexity
Solution Approach 2:
The system applies self-service by using the battery's own operational data (voltage, current, temperature) to automatically detect degradation and adjust capacity estimates. The system monitors its own performance characteristics and performs self-correction without requiring external intervention or additional complex measurement systems
Data Source
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AI summary
A battery management system includes a sensing unit and a main controller unit (MCU) is disclosed. In one aspect, the sensing unit is configured to measure a current value and a voltage value of a battery under a discharge condition of the battery. In addition, the MCU is configured to receive the current and voltage values and further configured to manage capacities of the battery based at least in part on the current and voltage values. In addition, the MCU includes a an unusable capacity calculating unit configured to calculate an unusable capacity corresponding to a portion of a theoretical maximum capacity of the battery that is unusable under the discharge condition, where the unusable capacity is calculated based at least in part on the current value and an internal resistance value of the battery under the discharge condition.