Battery Pack Equalization Using Cell-Wise Converter Output Control
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Solution Overview
Problem
Battery charge imbalance due to chemical and aging differences among cells leads to over-charging and over-discharging, causing degradation and reduced battery capacity and life.
Innovation Solution
A method and apparatus for battery equalization that involves verifying the output physical quantity of DC-DC converters, calculating average state information, and adjusting output values based on state differences to balance battery states, ensuring balanced charging and discharging across the battery pack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charging and discharging operations are repetitively performed on a plurality of cells, then battery capacity and power output are improved, but chemical differences and aging differences develop among cells causing charge imbalance and over-charging/over-discharging
Solution Approach 1:
The patent applies local quality by individually managing each battery cell's charge state through separate converters. Each converter is controlled based on the specific state of charge (SOC) of its corresponding cell, allowing differential treatment of cells with different aging and chemical characteristics. This enables the system to maintain charge balance by adjusting each cell's charging/discharging rate according to its individual needs rather than treating all cells uniformly.
Solution Approach 2:
The patent implements dynamics by continuously monitoring and dynamically adjusting the output values of converters based on real-time SOC measurements. The control system dynamically modifies charging/discharging rates during operation to maintain charge balance, adapting to changing cell conditions as aging and chemical differences evolve over time. This dynamic adjustment prevents over-charging and over-discharging while maximizing battery capacity utilization.
2Device complexity
If conventional battery management is used without equalization, then device complexity is reduced, but over-charging and over-discharging cause degradation and reduced battery life
Solution Approach 1:
The patent implements feedback by continuously monitoring the state of charge of each battery cell and using this information to adjust the output values of converters. The control system receives SOC feedback from each cell, compares it against target values, and dynamically modifies charging/discharging rates to maintain charge balance. This closed-loop feedback mechanism prevents over-charging and over-discharging, thereby extending battery life while managing system complexity through automated control.
Solution Approach 2:
The patent applies self-service by enabling the battery management system to automatically detect charge imbalances and correct them without external intervention. The control system autonomously monitors SOC levels, identifies cells that are over-charged or over-discharged, and adjusts converter outputs to equalize charge states. This self-correcting mechanism extends battery life by preventing degradation while maintaining relatively simple system architecture through automated equalization.
Data Source
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AI summary
A method and an apparatus for charge equalization of batteries, and a battery pack using such a method are provided. A method of charge equalization of batteries involves determining a ratio between first state difference information for each of the batteries and second state difference information calculated based on values of items included in the first state difference information, and defining an output value for each converter corresponding to each of the batteries based on the ratio.