Fast Charge Contactor Voltage-Drop Control in EV DC Charging
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Solution Overview
Problem
In electric vehicles, the high current and voltage during DC fast charging stress contactors, potentially reducing their durability, and existing systems lack effective methods to monitor contactor health beyond counting opening and closing events.
Innovation Solution
A controller adjusts the DC charge current based on voltage drop data across fast charge contactors, commanding a lower current if the drop is below a threshold and a higher current if above, discontinuing charging if excessive, and using voltage sensors to assess contactor health and trigger service notifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high DC charge current is used during fast charging, then charging speed is improved, but contactor durability deteriorates due to stress
Solution Approach 1:
The controller continuously monitors voltage drop across the contactor and adjusts the charge current accordingly. When voltage drop exceeds a threshold indicating contactor stress, the controller reduces current magnitude to prevent damage, thereby maintaining reliability while enabling fast charging capability.
Solution Approach 2:
The charge current magnitude is dynamically adjusted based on real-time contactor condition assessment through voltage drop monitoring. The system transitions between different current levels (high when contactor is healthy, reduced when stress is detected) to optimize both charging speed and contactor lifespan.
2Reliability
If voltage drop monitoring is implemented to assess contactor health, then contactor reliability is improved, but system complexity increases
Solution Approach 1:
The contactor effectively monitors its own health condition by measuring voltage drop across its terminals during normal operation. This self-diagnosis capability eliminates the need for separate monitoring hardware, reducing system complexity while improving reliability.
Solution Approach 2:
The voltage drop measurement serves multiple functions: it characterizes contactor resistance for health assessment, triggers service notifications when thresholds are exceeded, and provides feedback for dynamic current adjustment. This multi-functionality reduces the need for additional dedicated monitoring systems.
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 effectively monitors contactor health and prevents over-stressing, potentially extending contactor lifespan and ensuring safe charging operations by adjusting charge current in response to voltage drop thresholds.
Implementation Method 1
monitoring the voltage drop across the fast charge contactor during DC fast charging
Data Source
AI summary
A controller, during DC fast charge of a traction battery, commands a DC charge current to have a magnitude less than a predefined value and responsive to magnitudes of resulting voltage drop data for a fast charge contactor connected between a charge port and main contactor being less than a first threshold value, commands the DC charge current to have a magnitude at a target high value.