Inductor and FET Selection for Efficient Battery Cell Equalization
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Solution Overview
Problem
Current battery management systems (BMS) face challenges in efficiently balancing the state-of-charge (SOC) of battery cells due to the use of either passive or active equalizers, with passive EQUs causing energy loss and active EQUs being expensive, while bilevel equalizers (BEQs) require effective design tools to optimize performance and cost.
Innovation Solution
A method for selecting an inductor and a pair of FET switches for an active battery cell equalization circuit, involving determining design specifications, inductance, core design, winding turns, saturation levels, losses, and efficiencies, along with selecting appropriate FET switches to maximize charge transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive equalizers are used to balance battery cell voltages, then cost is reduced, but energy loss increases due to heat dissipation
Solution Approach 1:
The patent introduces an inductor as an intermediary energy storage element between battery cells. Instead of directly dissipating energy through resistors (passive EQU), the inductor temporarily stores energy and enables controlled charge transfer between cells, reducing energy loss while maintaining cost-effectiveness compared to full active equalization systems
2Loss of energy
If active equalizers are used to transfer charge between battery cells, then energy loss is reduced and performance is improved, but cost increases
Solution Approach 1:
The patent segments the equalization system into multiple battery cell groups, with active equalization applied selectively between groups rather than requiring full active equalization for every cell. This segmentation approach reduces the overall number of active equalization circuits needed, lowering cost while maintaining energy efficiency benefits in critical areas
Solution Approach 2:
The patent applies different equalization strategies to different parts of the battery system - active equalization with inductor-based energy transfer is used where energy efficiency is critical, while allowing passive equalization in less critical areas. This local differentiation optimizes the balance between cost and energy loss reduction
3Reliability
If bilevel equalizers are implemented to combine active and passive equalization, then performance接近 active EQU is achieved, but design complexity increases requiring effective design tools
Solution Approach 1:
The patent performs preliminary calculations and optimizations during the design phase, including determining optimal inductor values, switching frequencies, and circuit parameters before manufacturing. This preliminary action creates a standardized design framework that reduces the complexity of implementing bilevel equalization systems, as the complex parameters are pre-determined through systematic design tools and methodologies
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
The method enhances the efficiency and performance of BEQs by optimizing inductor and FET switch design, reducing energy loss and cost, thereby improving battery capacity and performance.
Implementation Method 1
determining an inductance of the inductor using the design specifications... determining total inductor losses for the selected core design... determines an efficiency for the selected core design
Implementation Method 2
selecting a potential pair of FET switches for the equalization circuit, determining switching losses and conduction losses of the selected FET switches
Data Source
AI summary
A method for selecting an inductor and a pair of FET switches for an active battery cell equalization circuit. The method includes determining inductor design specifications including an operating voltage, current and frequency of the equalization circuit; determining an inductance of the inductor using the design specifications; determining an inductor power of the inductor using the design specifications; selecting an inductor core design to be used in the inductor; determining the number of turns for the windings of the selected core design using the determined inductance; determining a level of saturation for the selected core design; determining inductor core losses for the selected core design; determining inductor winding losses for the selected core design; determining total inductor losses for the selected core design; and determining an efficiency for the selected core design. The method further includes determining switching losses and conduction losses and determining an efficiency of selected FET switches.