Reconfigurable Battery Charger Control for Voltage Imbalance
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Solution Overview
Problem
Vehicle battery packs with multiple parallel strings often experience voltage imbalances, which hinder their performance and prevent proper usage in parallel electrical circuits, necessitating an improved method for recharging.
Innovation Solution
A method that determines voltage imbalances between parallel strings and uses series circuits with external power supplies, electrical loads, or pulse width modulation to reduce these imbalances, allowing the strings to be reconnected in parallel for efficient power supply to the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel strings are connected directly for charging, then charging speed is fast, but voltage imbalance occurs between strings
Solution Approach 1:
The system performs preliminary detection of voltage imbalances before charging begins, and pre-balances the strings by connecting them in series and adjusting voltages to be within a threshold range, ensuring balanced charging conditions are established in advance
Solution Approach 2:
The system dynamically switches between parallel connection mode (for fast charging when voltages are balanced) and series connection mode (for voltage balancing when imbalances occur), allowing the charging strategy to adapt in real-time based on the voltage state of the battery strings
2Reliability
If series connection is used for voltage balancing, then voltage imbalance is reduced, but charging time increases
Solution Approach 1:
The system performs preliminary voltage balancing in series connection mode before switching to parallel charging, so that when parallel charging begins, the strings are already balanced and can charge simultaneously without requiring time-consuming balancing operations during the charging process
Solution Approach 2:
The system periodically monitors voltage imbalances during charging and temporarily switches to series connection for balancing when imbalances exceed the threshold, then returns to parallel connection for fast charging, creating a periodic cycle that maintains both speed and balance
3Productivity
If voltage balancing is performed during charging, then charging efficiency is maintained, but system complexity increases
Solution Approach 1:
The same switching network and control system are used for both charging operations and voltage balancing operations, allowing the system to perform multiple functions (parallel charging, series balancing, mode switching) without requiring separate dedicated hardware for each function
Solution Approach 2:
The system continuously monitors the voltage differences between parallel strings and uses this feedback to automatically determine when to switch between parallel and series connection modes, maintaining charging efficiency through closed-loop control without requiring complex manual intervention
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
This approach minimizes charging time and enhances the performance of vehicle battery packs by effectively addressing voltage imbalances, enabling faster and more efficient charging and power supply.
Implementation Method 1
connecting the first group of the cells in series with an external power supply, such that the voltage imbalance is electrically reduced by increasing the voltage potential of the first group of the cells
Implementation Method 2
the second group of the cells is connected in series with an electrical load, such that the voltage imbalance is electrically reduced by reducing the voltage potential of the second group of the cells
Implementation Method 3
a connection of an electrical load in series with the first group of cells and the second group of cells may be alternated using pulse width modulation, such that the voltage imbalance is electrically reduced by increasing the voltage potential of the first group of the cells and by reducing the voltage potential of the second group of the cells
Data Source
AI summary
Methods of charging a vehicle battery pack are disclosed. Example methods may include determining a voltage imbalance between at least two parallel strings of a battery pack exceeds a threshold magnitude. Methods may further include electrically reducing the voltage imbalance between the at least two parallel strings using a series circuit including a first group of one or more of the battery cells of a first one of the parallel strings, and reconnecting the parallel strings in an electrical circuit in parallel to each other, in which configuration the strings of the battery pack may supply power to the vehicle.