Battery Cell Balancing Duty-Cycle Control for Heat-Limited Packs
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Solution Overview
Problem
Existing cell-balancing methods in high-voltage batteries face challenges in reducing balancing time while maintaining heat radiation performance, as increasing balancing current leads to higher power consumption and heat generation, limiting the size and cost of the substrate.
Innovation Solution
A battery management system with multiple balancing resistors and switches, where the battery controller calculates and scales duty cycles based on cell capacities and power consumption limits to optimize balancing efficiency and reduce heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the balancing current is increased to reduce balancing time, then the balancing time is reduced, but the power consumption and heat generation increase
Solution Approach 1:
The patent implements dynamic adjustment of duty cycles for balancing switches based on real-time cell voltage differences and power consumption limits. The controller continuously monitors the state of charge of each cell and adjusts the balancing current dynamically, allowing higher currents when power headroom is available and reducing currents when approaching thermal limits, thus resolving the contradiction between fast balancing and heat management
Solution Approach 2:
The patent employs periodic balancing operations with pulsed duty cycles rather than continuous balancing. By applying balancing current in periodic pulses and introducing duty cycle ratios, the system achieves effective balancing over time while allowing heat dissipation during off-periods, thereby reducing peak power consumption and heat generation while maintaining acceptable balancing speeds
2Loss of time
If the balancing current is increased to reduce balancing time, then the balancing time is reduced, but the heat radiation performance deteriorates
Solution Approach 1:
The patent applies different duty cycle ratios to different balancing switches based on local conditions of each cell and its position in the battery pack. Cells with higher voltage deviations receive higher duty cycles, while cells closer to thermal limits receive lower duty cycles. This localized control allows the system to achieve fast balancing where possible while protecting thermal-sensitive areas, resolving the contradiction between balancing speed and heat radiation performance
Solution Approach 2:
The controller acts as an intermediary between the balancing current source and the cells, mediating the power delivery through intelligent duty cycle management. It translates the conflicting requirements of fast balancing and heat management into optimized switching patterns, effectively decoupling the direct relationship between balancing current magnitude and heat generation by introducing temporal distribution of energy delivery
3Productivity
If the balancing current is increased, then the balancing efficiency is improved, but the substrate size and material cost increase
Solution Approach 1:
The patent enables the battery management system to self-regulate the balancing process by autonomously monitoring cell states and adjusting duty cycles without external intervention. The system uses its own sensing capabilities and control algorithms to optimize balancing efficiency within thermal constraints, eliminating the need for oversized passive cooling structures and achieving high balancing efficiency with compact substrate design
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 solution effectively reduces balancing time while maintaining heat radiation performance by optimizing duty cycles and power consumption, allowing for increased balancing current without excessive heat generation.
Implementation Method 1
The passive cell-balancing method uses a simple control method or a simple control circuit, but power generated by a discharging is consumed through heat
Data Source
AI summary
A battery management system may include a plurality of balancing resistors respectively forming balancing discharging paths of cells connected in series to each other, a plurality of balancing switches respectively connected between the cells and the balancing resistors, and configured to control cell-balancing of each of the cells, a voltage-detecting circuit for detecting respective cell voltages of the cells, and a battery controller for acquiring respective balancing capacities of the cells based on the cell voltages, for obtaining duty cycles of the balancing switches according to the balancing capacities, and for scaling the duty cycles of the balancing switches according to a sum of duty cycles of two adjacent cells from among the cells.