Dynamic Passive Cell Balancing for Faster EV Battery Equalization
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Solution Overview
Problem
Conventional passive cell balancing techniques for electrified vehicles suffer from slow speeds and poor accuracy due to fixed resistance limiting discharge/balancing current, leading to charge imbalance and decreased vehicle range.
Innovation Solution
A passive dynamic cell balancing system that utilizes a variable or dynamic load, such as a switching mode or linear dynamic load, to control balancing current, incorporating state of charge deviation detection and variable gain for improved accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional passive cell balancing with fixed resistance is used, then the system structure remains simple, but the balancing speed and accuracy deteriorate
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed resistance to variable resistance that dynamically adjusts based on cell state. The control system continuously monitors cell voltages and SOCs, then adjusts the resistance values in real-time to optimize balancing current flow, thereby improving balancing speed and accuracy without requiring a fundamentally complex system architecture.
Solution Approach 2:
The patent implements parameter changes by modifying the resistance parameter dynamically during the balancing process. The control system adjusts resistance values based on measured cell parameters (voltage, SOC) to optimize the balancing current. This allows the system to adapt to changing battery conditions and achieve faster, more accurate balancing while maintaining relative system simplicity.
2Device complexity
If conventional passive cell balancing with fixed resistance is used, then the system structure remains simple, but the balancing accuracy deteriorates
Solution Approach 1:
The patent applies feedback by implementing a control system that continuously monitors cell voltages and SOCs, compares them against target values, and adjusts the resistance parameters accordingly. This closed-loop feedback mechanism enables the system to achieve high balancing accuracy by dynamically responding to cell state changes, while the overall system structure remains relatively simple through efficient control algorithms.
Solution Approach 2:
The patent uses parameter changes to improve balancing accuracy by dynamically adjusting resistance values based on real-time cell measurements. The control system modifies resistance parameters in response to measured cell voltages and SOCs, enabling precise control of balancing currents to achieve accurate cell matching without requiring complex hardware modifications.
3Device complexity
If passive cell balancing is used instead of active cell balancing, then device complexity is reduced, but balancing speed deteriorates
Solution Approach 1:
The patent bridges the gap between passive and active balancing by implementing a dynamic passive balancing system. The variable resistance allows the passive system to adjust its characteristics in real-time, enabling faster balancing speeds comparable to active systems while maintaining the simpler passive architecture. The dynamic adjustment of resistance compensates for the inherent speed limitation of passive balancing.
Solution Approach 2:
The patent uses parameter changes to overcome the speed limitation of passive balancing. By dynamically adjusting resistance parameters based on cell state, the system optimizes balancing current flow rates, achieving faster balancing speeds while retaining the passive energy dissipation approach. This eliminates the need for complex active energy transfer mechanisms.
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
Enhances charge/discharge performance and increases vehicle range by up to 5 kilometers through precise balancing current control.
Implementation Method 1
passive cell balancing, which is simpler and involves dissipating excess energy from higher charged cells
Data Source
AI summary
A passive dynamic cell balancing system for an electrified vehicle includes a dynamic load system configured to vary a balancing current output to a battery system of the electrified vehicle, wherein the battery system comprises a plurality of battery cells, and a control system configured to estimate a charge imbalance across the plurality of battery cells by estimating a state of charge (SOC) of each of the plurality of battery cells, estimate a balancing current for each of the plurality of battery cells based on their respective estimated SOCs, and controlling the variable load system based on the estimated balancing currents to dissipate a desired amount of electrical energy from each of the plurality of battery cells to resolve the estimated charge imbalance.