EV Battery Cell Switching for DC Link Precharge
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Solution Overview
Problem
Conventional electric vehicle precharging methods require a discrete precharging resistor to manage large electric currents during DC link capacitor charging, which can be costly and prone to failure.
Innovation Solution
A method that incrementally connects multiple battery cells to the electrical component via switching units, using parasitic impedance for current limiting without additional components, allowing for a soft start and efficient energy supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discrete precharging resistor is used to limit current during DC link capacitor charging, then large electric currents are controlled within an uncritical range, but the device complexity increases and the risk of failure increases
Solution Approach 1:
The patent extracts the precharging function from a separate discrete resistor component and integrates it into the battery management system through software control. The battery management system selectively activates or deactivates individual battery cells to inherently limit current during DC link capacitor charging, eliminating the need for external precharging resistors and their associated relays.
Solution Approach 2:
The battery management system uses the battery's own cellular structure and control capabilities to perform precharging. By controlling which battery cells are active during startup, the system self-regulates the charging current without requiring external passive components, making the battery system serve its own precharging needs.
2Ease of manufacture
If a precharging resistor is used to manage inrush current, then the DC link capacitor is charged safely, but additional components and switching elements are required
Solution Approach 1:
The patent merges the precharging function with the existing battery management system and battery cell structure. The battery management system combines control of multiple battery cells to achieve current limiting, integrating what would traditionally be a separate precharging circuit into the battery's native control architecture, thereby reducing total component count.
Solution Approach 2:
The battery management system performs multiple functions: it manages normal battery operation and simultaneously handles precharging by selectively activating/deactivating battery cells. This multi-functionality eliminates the need for dedicated precharging components, as the same control system serves both purposes.
3Device complexity
If battery cells are incrementally connected via switching units, then current is limited without additional precharging components, but the control complexity increases
Solution Approach 1:
The patent segments the battery into multiple independently controllable cells, each with its own switching unit. During precharging, the battery management system activates cells incrementally rather than all at once, using the segmentation to inherently limit current. This transforms a single complex precharging control problem into simpler sequential cell activation.
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 reduces the need for precharging components, improves precharging quality, and lowers the risk of failure while providing a reliable energy supply for electric vehicle components.
Implementation Method 1
using parasitic impedance for current limiting without additional components
Data Source
AI summary
A method for operating at least one electrical component of a vehicle with the aid of a battery. At least two battery cells of the battery are electrically connected and thus added to the at least one component via at least one particular switching unit. The following steps for precharging a DC link of the vehicle is carried out: a) adding a first of the battery cells, b) incrementally adding at least a second of the battery cells, after a previous adding has taken place in each case.