Dynamic Precharge Timing for Electric Vehicle Powertrain
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Solution Overview
Problem
Electric vehicles experience high in-rush currents during start-up due to the capacitance in their powertrains, which can damage components, and existing precharge circuits may not effectively manage this issue under varying conditions.
Innovation Solution
The method involves intentionally varying the precharge time by adjusting the duration of the precharge period based on conditions such as remote start, occupancy, and charging status, using a controller to manage the precharge contactor and main contactors to route current through a resistor, thereby reducing in-rush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery is reconnected to the powertrain at start-up, then the battery is reconnected to the portions of the powertrain, but high in-rush current damages components
Solution Approach 1:
The precharge contactor closes before the main contactor to precharge the powertrain capacitance through the precharge resistor, limiting in-rush current before the main power connection is established. This preliminary action prevents damaging current spikes when the battery is reconnected to the powertrain.
Solution Approach 2:
The precharge resistor serves as an intermediary element that temporarily limits current flow during the transition phase. By routing current through this high-resistance path before switching to the low-resistance main contactor path, the system mediates the harmful in-rush current effect.
2Adaptability or versatility
If a fixed precharge time is used, then the precharge circuit limits in-rush current, but it may not effectively manage the issue under varying conditions
Solution Approach 1:
The precharge time is changed from a fixed value to a dynamic parameter that varies based on vehicle conditions. The controller adjusts the precharge duration according to whether the vehicle is remotely started, occupied, or charging, allowing the system to adapt to different operational scenarios while maintaining reliable in-rush current management.
Solution Approach 2:
The system uses feedback from vehicle state sensors (remote start status, occupancy sensors, charging status) to dynamically adjust the precharge timing. This feedback mechanism enables the precharge circuit to respond to varying conditions and optimize its operation for each specific scenario.
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 reduces in-rush currents, prolongs the life of powertrain components, and ensures safe and efficient start-up by optimizing the precharge time based on specific conditions.
Implementation Method 1
The precharge circuit limits in-rush current by routing current through the precharge resistor
Implementation Method 2
The powertrain of an electric vehicle has significant capacitance. The capacitance has a very low resistance and can cause a large amount of in-rush current when the battery is reconnected and the capacitance charges
Data Source
AI summary
An example method includes intentionally precharging a powertrain of an electric vehicle for an first time period that is different than a second precharge time period. An example electric vehicle assembly includes a precharge contactor transitionable back and forth between an open state and a closed state, a first main contactor, a second main contactor, and a controller configured to selectively close the second main contactor after the precharge contactor has been closed for a first time period that is different than a second precharge time period.