Bilevel Battery Equalizer Combining Resistive and Switching Topologies
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Solution Overview
Problem
Current battery charge management systems, particularly charge equalizers, face inefficiencies and high costs, with resistive equalizers losing energy and being inexpensive but ineffective during discharge, while switching equalizers are complex and costly, limiting the overall performance and lifespan of battery packs.
Innovation Solution
A bilevel equalizer system combining resistive and switching equalizers, where resistive equalizers are used within sections of the battery pack to balance cell voltages and switching equalizers between sections to equalize section voltages, providing efficient charge management during both charge and discharge cycles at a reduced cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resistive equalizers are used to balance cell voltages, then cost is reduced and simplicity is improved, but energy loss increases and efficiency deteriorates
Solution Approach 1:
The battery pack is divided into multiple sections, with resistive equalizers applied at the section level rather than individual cell level. This segmentation reduces the number of equalizers needed, lowering cost while minimizing total energy loss through targeted equalization of section voltages.
Solution Approach 2:
Switching equalizers are introduced as intermediary devices between sections to transfer charge efficiently without resistive losses. These switching equalizers act as mediators that enable energy-efficient charge redistribution between sections, complementing the resistive equalizers at the section level.
2Loss of energy
If switching equalizers are used to transfer charge between cells, then efficiency is improved and energy loss is reduced, but device complexity and cost increase
Solution Approach 1:
The equalizer system is segmented into two levels: switching equalizers operating at the section level and resistive equalizers at the cell level within each section. This segmentation allows switching equalizers to handle only inter-section charge transfer, reducing their number and overall system complexity while maintaining efficiency.
Solution Approach 2:
The patent merges resistive and switching equalizer technologies into a unified bilevel system. Each approach complements the other: switching equalizers provide efficient inter-section charge transfer, while resistive equalizers handle intra-section balancing, creating a synergistic system that achieves high efficiency without excessive complexity.
3Productivity
If resistive equalizers are used during charging, then charge balancing is achieved, but discharge capacity is not improved
Solution Approach 1:
The equalizer system dynamically adapts its operation mode based on battery pack needs. During charging, resistive equalizers balance cell voltages within sections. During discharge, switching equalizers actively transfer charge to maintain optimal charge distribution, maximizing discharge capacity. The system transitions between these modes to optimize performance for each operational phase.
Solution Approach 2:
The bilevel equalizer system performs multiple functions: it balances cell voltages during charging like traditional resistive equalizers, and simultaneously maximizes discharge capacity through active charge transfer during discharge. This multi-functionality allows a single system to address both charge balancing and discharge capacity enhancement needs.
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 bilevel equalizer system enhances battery pack capacity and efficiency by maintaining voltages across all cells, offering performance comparable to switching equalizers at the cost of resistive equalizers, thus extending the usable capacity and lifespan of battery packs.
Implementation Method 1
REQs remove charge from the weakest cells during charging by connecting resistors in parallel with the higher voltage cells to divert current. REQs dissipate energy to bleed down the weak cells
Implementation Method 2
SEQs use high frequency switching circuits to transfer charge from weaker to strong cells during charge cycles, and vice versa during discharge cycles
Data Source
AI summary
An equalizer circuit provides both passive and active charge transfer between cells in a battery pack to improve charge and discharge efficiency. The equalizer circuit is a bilevel circuit that uses both resistive equalizers and switching equalizers to balance cell charge. The cells may be grouped into size limited sections which are balanced by resistive equalizers. The sections are balanced by switching equalizers to promote increased pack discharge capacity.