Battery Control Apparatus Using Discharge Capacity for Cell Balancing
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Solution Overview
Problem
Secondary batteries undergo accelerated degradation due to internal resistance increases from repeated charge/discharge cycles, leading to uneven cell capacity values and incorrect SOC calculations, resulting in over-charge and over-discharge conditions that accelerate cell degradation.
Innovation Solution
A battery control apparatus with voltage detection, charging rate calculation, current integration, cell capacity estimation, dischargeable capacity calculation, and control units to manage charging/discharging based on individual cell capacity values, preventing over-charge and over-discharge by maintaining balanced SOC levels across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization is performed based on open-circuit voltage for degraded cells, then voltage equalization is achieved, but cell degradation is accelerated due to repeated charge/discharge cycles
Solution Approach 1:
The patent changes the equalization parameter from open-circuit voltage to discharge capacity. By measuring the discharge capacity of each cell and equalizing based on capacity differences rather than voltage differences, the system avoids unnecessary charge/discharge cycles for cells that appear voltage-equalized but have different actual capacities, thereby reducing degradation while maintaining equalization effectiveness
Solution Approach 2:
The patent replaces the voltage-based equalization mechanism with a capacity-based equalization mechanism. Instead of using voltage measurements and corresponding charge/discharge operations, the system uses discharge capacity measurements to determine equalization needs, substituting the control variable and reducing harmful operational cycles
2Device complexity
If average voltage is used for SOC calculation, then calculation is simplified, but accuracy is reduced due to cell capacity variations from degradation
Solution Approach 1:
The patent applies local quality by calculating SOC individually for each cell based on its specific discharge capacity rather than using a uniform average voltage approach. Each cell's SOC is determined by its own discharge capacity characteristics, accounting for individual degradation levels and capacity variations, thereby improving overall SOC accuracy while maintaining manageable calculation complexity
3Stability of the object's composition
If charge/discharge cycles are performed for equalization, then SOC is equalized, but internal resistance increases due to repeated degradation
Solution Approach 1:
The patent performs preliminary measurement of discharge capacity for each cell before equalization operations. By预先 measuring and comparing discharge capacities, the system can identify which cells actually require equalization and target only those cells, avoiding unnecessary charge/discharge cycles for cells that are already balanced, thereby maintaining SOC uniformity while minimizing degradation-induced internal resistance increase
Data Source
AI summary
It is intended to prevent degradation of battery cells (cells). A battery control apparatus obtains a cell voltage value of each of the cells (201) (S1), calculates a cell SOC at each of the cells based on the measured cell voltage value (S2), calculates an integrated current value (Ah) by integrating current values of a battery pack (2) configured with a plurality of the cells (201), calculates a cell capacity value of each of the cells (201) based on the integrated current value and the cell SOC (S3), calculates a dischargeable cell capacity value from the cell capacity value and the cell SOC (S4), and controls charging/discharging of the battery pack (2) based on the dischargeable cell capacity value (S5).