Battery Cell SOC Change Analysis for Internal Short Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting internal short circuit faults in battery cells connected in series are inaccurate due to factors like full charge capacity, degradation level, temperature, and internal resistance, and require battery cells to remain undisturbed for extended periods.
Innovation Solution
A battery management system that utilizes state of charge (SOC) changes during charging and/or discharging of battery cells to detect internal short circuit faults. The system includes a sensing circuit to acquire state parameters and a control circuit that applies SOC estimation and statistical algorithms to determine reference factors and detect faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage difference or voltage drop methods are used to detect internal short circuit faults, then fault detection can be performed, but the detection accuracy is low due to interference from full charge capacity, degradation level, temperature, and internal resistance
Solution Approach 1:
The patent changes the detection parameter from voltage-based measurements (which are affected by multiple factors) to SOC-based measurements during charging/discharging. By monitoring SOC changes at different states of charge and comparing them, the method achieves more accurate fault detection that is less sensitive to temperature, internal resistance, and degradation variations
Solution Approach 2:
The patent introduces SOC (state of charge) as an intermediary parameter to detect internal short circuits. Instead of directly measuring voltage differences, the system uses SOC changes during charging and discharging as a mediator that reflects the health status of battery cells more accurately, filtering out the effects of temperature and internal resistance
2Measurement precision
If voltage drop method is used to detect internal short circuit faults, then fault detection is possible, but battery cells must remain undisturbed for extended periods (few hours to few days)
Solution Approach 1:
The patent enables continuous fault detection during normal charging and discharging operations. Instead of requiring the battery to be at rest for extended periods, the system continuously monitors SOC changes during active use, allowing real-time fault detection without interrupting battery operation or requiring prolonged idle time
Solution Approach 2:
The patent performs preliminary SOC measurements at multiple points during charging and discharging cycles. By taking SOC readings at different states of charge before and during operation, the system can detect faults in real-time without waiting for the battery to settle, eliminating the need for extended rest periods required by traditional voltage drop methods
3Ease of operation
If minimum voltage and maximum voltage parameters are used for fault detection, then simple measurement is possible, but accuracy is low because these parameters are greatly affected by other factors
Solution Approach 1:
The patent transitions from using minimum and maximum voltage parameters to using SOC change parameters during charging/discharging. This parameter change maintains operational simplicity while significantly improving accuracy, as SOC changes are less influenced by temperature, internal resistance, and degradation effects compared to voltage measurements
Data Source
AI summary
A battery management system includes a sensing circuit to acquire a state parameter of each of a plurality of battery cells connected in series; and a control circuit to determine, for each battery cell, a first state of charge (SOC) change which is a difference between a first SOC at a first charge time and a second SOC at a second charge time by applying a SOC estimation algorithm to the state parameter acquired during charging. The control circuit determines a reference factor by applying a statistical algorithm to the first SOC changes of at least two of the plurality of battery cells. The control circuit detects an internal short circuit fault in each battery cell based on the first SOC change of each battery cell and the reference factor.