Traction Battery Leakage Detection via Capacitive Coupling
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Solution Overview
Problem
Leakage currents associated with traction batteries in vehicles are not effectively detected and inhibited by existing technologies, leading to potential battery performance issues and safety concerns.
Innovation Solution
A test circuit and controller system that selectively attaches to a traction battery cell via a transistor, using a voltage sensor to monitor a test capacitor's charge and discharge rates, and inhibiting battery operation if predetermined thresholds are not met, thereby preventing excessive leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing technologies are used to monitor battery leakage, then the system structure remains simple, but leakage currents are not effectively detected and inhibited
Solution Approach 1:
A test capacitor is introduced as an intermediary component between the battery terminal and the voltage sensor. The capacitor serves as a mediator that accumulates leakage current, allowing indirect measurement through voltage monitoring across the capacitor. This enables effective leakage detection without requiring direct complex measurement circuits at the battery terminal.
Solution Approach 2:
The patent replaces direct electrical measurement methods with a capacitive coupling approach. Instead of using complex current sensing circuits, the system uses a voltage sensor to monitor the voltage across the test capacitor, which indirectly reflects the leakage current. This substitution simplifies the measurement system while maintaining detection effectiveness.
2Measurement precision
If continuous monitoring of battery leakage is implemented, then detection accuracy improves, but energy consumption increases
Solution Approach 1:
The monitoring system operates periodically rather than continuously. The controller periodically reads the voltage across the test capacitor to detect leakage currents. This periodic sampling approach maintains adequate detection accuracy while significantly reducing the energy consumption compared to continuous monitoring.
Solution Approach 2:
The test capacitor naturally accumulates leakage current during normal battery operation without requiring active pumping or external energy input. The leakage current itself charges the capacitor, creating a self-service mechanism where the monitored phenomenon directly provides the measurement signal, minimizing additional energy requirements.
3Reliability
If high threshold sensitivity is used to detect leakage currents, then detection capability improves, but false inhibition of battery operation increases
Solution Approach 1:
The controller implements feedback by periodically reading the voltage across the test capacitor and comparing it against threshold values. This feedback mechanism allows the system to adaptively monitor leakage levels and only inhibit battery operation when the voltage (and thus leakage current) exceeds predetermined thresholds, reducing false inhibitions while maintaining reliable detection capability.
Solution Approach 2:
The system uses predetermined voltage thresholds as change points to determine when leakage currents require intervention. By establishing specific voltage threshold values that correspond to safe operating limits, the system can reliably detect problematic leakage conditions while avoiding unnecessary battery shutdowns for minor, acceptable variations in leakage current.
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
Effectively detects and prevents leakage currents by monitoring charge and discharge rates, ensuring the traction battery operates within safe parameters and maintaining battery health.
Implementation Method 1
a voltage sensor disposed across a test capacitor indicative of the voltage of the test capacitor
Implementation Method 2
operate the transistor such that electrical current from the one of the positive terminal and negative terminal is inverted within the test circuit
Data Source
AI summary
A circuit is selectively attachable to one of a positive terminal and negative terminal of a traction battery cell via a transistor. The circuit has a current sensor disposed in series with an inductor. A controller operates the transistor such that electrical current from the one of the positive terminal and negative terminal is inverted within the circuit, and while an inductor charge rate is less than a predetermined charge value, inhibits charge and discharge of the traction battery cell.