Battery Contactor Weld Detection Using Voltage Drop and RC Dynamics
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Solution Overview
Problem
Electric vehicles face the challenge of contactor welding due to high electric currents, which can cause unintended connections between the traction battery and the vehicle chassis, leading to increased resistance and voltage drops, potentially preventing the vehicle from starting.
Innovation Solution
A system and method that includes a controller generating commands to open contactors and inhibiting vehicle startup based on sensed voltage and current changes, detecting increased resistance and voltage drops across electrical buses, and using RC dynamics to determine contactor weld status, thereby preventing further damage and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactors remain closed due to welding, then electrical connection is maintained, but vehicle reliability deteriorates and potential damage occurs
Solution Approach 1:
The system performs preliminary detection by commanding contactors to open and monitoring voltage/current changes before actual welding damage occurs. The controller detects resistance changes and voltage drops that indicate welding conditions, preventing further operation that would cause damage.
Solution Approach 2:
The system continuously monitors voltage and current parameters across contactors, providing feedback to the controller. When abnormal changes are detected (resistance increase, voltage drop), the controller receives this feedback and inhibits vehicle start, preventing welding-related damage.
2Object-affected harmful factors
If vehicle startup is inhibited when contactor weld is detected, then safety is improved, but productivity decreases due to restricted operation
Solution Approach 1:
The controller receives feedback from voltage and current sensors to determine contactor status. Based on this feedback, the controller intelligently decides whether to inhibit startup, only restricting operation when actual welding conditions are detected, not for normal operations.
Solution Approach 2:
The system performs self-diagnosis by monitoring its own electrical parameters. The controller automatically detects welding conditions through voltage/current monitoring and takes corrective action (inhibiting startup) without external intervention, ensuring safety while maintaining operational autonomy.
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 contactor welding by inhibiting vehicle startup when abnormal resistance and voltage conditions are detected, ensuring reliable electrical connections and preventing potential damage to the vehicle's electrical system.
Implementation Method 1
using RC dynamics to determine contactor weld status
Implementation Method 2
detecting increased resistance and voltage drops across electrical buses
Data Source
AI summary
A power system includes a battery and a controller. The controller inhibits charge of the battery according to voltage or current values sensed before and after contactors electrically connected to the battery are commanded to open and indicating that a leakage resistance associated with one of the contactors increases after the one of contactors is commanded to open, and a duration of a continuous voltage drop across another of the contactors after the another of the contactors is commanded to open exceeds a threshold.