Battery Pack Charging Balancing via Electromotive Force Calculation
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Solution Overview
Problem
Current battery pack balancing methods inaccurately determine which cells need balancing due to increasing internal resistance differences over time, leading to reduced accuracy and reliability in charging.
Innovation Solution
A battery pack system that acquires internal resistance and terminal voltage of each cell in real time during constant current charging, calculates the electromotive force, and identifies a target cell for balancing management based on these values to ensure accurate charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If terminal voltage difference method is used for cell balancing determination, then the balancing process is simple to implement, but the accuracy and reliability of balancing determination decreases over time due to internal resistance differences
Solution Approach 1:
The patent changes the parameter used for balancing determination from terminal voltage to electromotive force. By calculating electromotive force using the formula E = U + Ir (where E is electromotive force, U is terminal voltage, I is charging current, and r is internal resistance), the system compensates for voltage drops caused by internal resistance differences, thereby maintaining high accuracy in balancing determination over time without sacrificing implementation simplicity
Solution Approach 2:
The patent introduces electromotive force as an intermediary parameter between terminal voltage and cell state. Instead of directly using terminal voltage for balancing determination, the system first calculates electromotive force by adding the internal resistance voltage drop (Ir) to the terminal voltage (U), then uses this intermediary value for accurate cell balancing decisions
2Measurement precision
If internal resistance compensation method is used to calculate electromotive force, then the accuracy of balancing determination is improved, but the complexity of the charging system increases
Solution Approach 1:
The control module performs self-service by automatically acquiring internal resistance values for each cell and using these values to calculate electromotive force during the charging process. The system uses its own existing resources (control module, sensors) to implement the compensation calculation without requiring external assistance or additional complex equipment
Solution Approach 2:
The control module is designed to perform multiple functions: it manages charging control, acquires terminal voltage data, stores internal resistance values, calculates electromotive force, and determines balancing needs. By making the control module universal and multi-functional, the patent avoids adding separate dedicated hardware for each function, thereby limiting the increase in system complexity
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 improves the accuracy and reliability of charging balancing by accurately determining the target cell for balancing, thereby maintaining optimal cell performance over time.
Implementation Method 1
a first battery cell group and a second battery cell group in the battery pack are respectively charged to different charging states
Data Source
AI summary
A battery pack includes a plurality of cells and a control module. The control module is configured to acquire internal resistance of each of the plurality of cells, acquire a terminal voltage of each of the plurality of cells in real time in a case where the plurality of cells are charged with a constant current, determine an electromotive force of each of the plurality of cells based on the internal resistance of each of the plurality of cells and a charging current and the terminal voltage, determine a target cell from the plurality of cells based on the electromotive force of each of the plurality of cells, and perform charging balancing management on the target cell.