Hybrid Battery Cell Balancing for Low-SOC Equalization
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Solution Overview
Problem
Battery cells in a battery pack or rack experience varying degrees of degradation due to manufacturing and usage differences, leading to inconsistent state of charge (SOC), which existing balancing technologies fail to efficiently address.
Innovation Solution
An apparatus and method for battery cell balancing that performs active balancing on the cell with the lowest SOC and passive balancing on higher SOC cells, using a system of passive balancing resistors, switches, and a charging element controlled by a battery management system to equalize SOC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If passive balancing is performed on all battery cells, then the balancing operation can be performed, but energy waste increases due to discharging cells that do not need balancing
Solution Approach 1:
The patent applies local quality by differentiating the balancing approach for different battery cells based on their individual SOC levels. Specifically, only cells with SOC above a reference threshold undergo passive balancing, while the cell with the lowest SOC receives active balancing. This selective application of different balancing methods to different parts of the battery system minimizes unnecessary energy discharge while maintaining effective balancing performance.
2Productivity
If active balancing is performed on all battery cells, then balancing can be achieved, but device complexity and cost increase
Solution Approach 1:
The patent segments the battery balancing system into two distinct groups: cells requiring active balancing (those with lowest SOC) and cells requiring passive balancing (those with higher SOC). This segmentation allows the system to apply the more complex and expensive active balancing method only where necessary, while using the simpler passive balancing method for the majority of cells, thereby reducing overall system complexity and cost.
Solution Approach 2:
The patent applies partial action by performing active balancing on only one cell at a time (the cell with the lowest SOC) rather than simultaneously on all cells. This partial application of active balancing reduces the complexity of the switching network and control system while still achieving effective overall balancing through the combination with passive balancing on other cells.
3Device complexity
If only passive balancing is used, then the system is simple, but energy waste increases and balancing speed decreases
Solution Approach 1:
The patent introduces a charging element as an intermediary component that enables active balancing by transferring charge from cells with higher SOC to the cell with lowest SOC. This intermediary charging element allows the system to recover and reuse energy that would otherwise be wasted, converting it into useful charging capacity for the deficient cell, thereby reducing overall energy waste while maintaining system simplicity.
4Loss of time
If balancing is performed on all cells simultaneously, then balancing time is reduced, but energy waste and system complexity increase
Solution Approach 1:
The patent implements periodic action by sequentially performing active balancing on different cells in multiple stages rather than attempting to balance all cells simultaneously. The battery management system identifies the cell with the lowest SOC, performs active balancing on that cell, then re-evaluates and moves to the next cell with the lowest SOC. This periodic, iterative approach achieves comprehensive balancing over time while minimizing energy waste and system complexity at any given moment.
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
Rapidly balances battery cells while minimizing energy waste and monitoring cell states, preventing accelerated degradation and ensuring efficient power utilization.
Implementation Method 1
a charging element configured to convert power received from a power source for active balancing and supply a result of conversion to the plurality of battery cells
Implementation Method 2
a plurality of passive balancing resistors respectively connected in parallel to a plurality of battery cells
Data Source
AI summary
Proposed are an apparatus and a method for battery cell balancing. The apparatus includes passive balancing resistors respectively connected in parallel to battery cells, passive balancing switches respectively connected in series to the passive balancing resistors and connecting or disconnecting the passive balancing resistors in parallel to or from the battery cells, a charging element converting power and supplying a result of conversion to the battery cells, switching elements respectively connected to the battery cells and connecting or disconnecting the battery cells to or from the charging element, and a battery management system sensing states of charge of the battery cells and controlling the passive balancing switches or the switching elements such that active balancing is performed on one battery cell with the lowest state of charge and passive balancing is performed on one or more battery cells with the states of charge higher than a reference value.