Battery Cell Internal Short Detection via Balancing Frequency
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Solution Overview
Problem
Existing rechargeable battery systems face challenges in detecting internal shorts and imbalances among battery cells, which can lead to thermal runaway events due to the limitations of external temperature monitoring and the variability in wear and use patterns among cells and modules.
Innovation Solution
A method involving a microprocessor that monitors and counts the frequency of balancing operations for each battery cell, marking cells as faulty when a threshold is exceeded, using Coulomb counting and differential testing to detect internal shorts before they cause thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external temperature monitoring is used to detect internal shorts, then thermal runaway events can be detected, but detection reliability is insufficient because internal shorts often occur without causing detectable temperature increase
Solution Approach 1:
The patent uses balancing operation counts as an intermediary indicator to detect internal shorts. Instead of directly measuring temperature (which fails to detect hidden faults), the system monitors the number of times balancing operations are performed on each cell. An abnormal increase in balancing frequency serves as a proxy indicator of internal short conditions, enabling detection before thermal runaway occurs.
Solution Approach 2:
The system implements feedback by continuously monitoring balancing operation counts and comparing them against threshold values. When the balancing count exceeds the threshold, the system generates a fault indication. This closed-loop feedback mechanism enables continuous assessment of cell health based on operational patterns rather than relying on direct temperature measurement.
2Reliability
If battery cells are monitored using traditional methods, then basic operation status can be tracked, but internal shorts and imbalances cannot be detected early enough to prevent thermal runaway
Solution Approach 1:
The system performs preliminary detection by monitoring balancing operation counts before thermal runaway occurs. Internal shorts cause increased self-discharge, which triggers more frequent balancing operations. By detecting this pattern early through count monitoring, the system identifies faults in the preliminary stage, allowing preventive action before the condition escalates to thermal runaway.
Solution Approach 2:
The patent implements a threshold-based warning system that provides advance notice of potential failures. By setting a threshold for balancing operation counts and alerting when approached, the system creates a safety buffer that allows preventive maintenance or system shutdown before the actual failure occurs, cushioning against the harmful effects of thermal runaway.
3Stability of the object's composition
If balancing operations are performed frequently to maintain cell balance, then cell balance is improved, but excessive balancing may indicate or accelerate internal short conditions
Solution Approach 1:
The system uses feedback by monitoring the frequency of balancing operations and using this information to detect potential internal shorts. When a cell requires balancing more frequently than others, the system counts these operations and compares against thresholds. This feedback loop transforms the balancing process from a purely corrective action into a diagnostic tool that can identify cells with internal issues.
Solution Approach 2:
The balancing operation count serves as an intermediary metric that links the balancing process to cell health assessment. Rather than directly measuring internal short conditions, the system uses the frequency of balancing operations as a proxy indicator. This intermediary measurement enables indirect detection of cell degradation and internal faults.
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
This approach allows for early detection of potentially faulty battery cells, preventing thermal runaway events and ensuring safer operation by identifying internal shorts and imbalances through monitoring balancing cycles, thereby enhancing the reliability and safety of battery systems.
Implementation Method 1
using Coulomb counting and differential testing to detect internal shorts before they cause thermal runaway
Data Source
AI summary
Internal shorts and other failures in lithium-ion battery cells may be detected during balancing of the battery cells. A counter may be used to detect when a battery cell is behaving differently than other battery cells by balancing more or less frequently. The counter may increment each time a battery cell is balanced to the other battery cells. A misbehaving battery cell may be flagged, when the counter exceeds a threshold value, for safety checks before an overheating event occurs. This misbehaving battery cell may be faulty due to an internal short. If the faulty battery cell is not corrected by replacement with a different battery cell or corrected by a user resetting the counter, the misbehaving battery cell may be disconnected to prevent the overheating event.